Thyroid Function Test (TFT) Explained: Normal Range, TSH, T3, T4, High & Low Levels (India 2026) | थायरॉइड फंक्शन टेस्ट गाइड
Thyroid Function Test (TFT) Explained: Normal Range, TSH, T3, T4, High & Low Levels (India 2026)
थायरॉइड फंक्शन टेस्ट गाइड: TSH, T3, T4 — नॉर्मल रेंज, Hypothyroidism, Hyperthyroidism, Report Reading और Medication Monitoring — पूरी जानकारी
Your routine health check has flagged a TSH of 8.4 mIU/L — and you are trying to understand whether you have hypothyroidism and whether you need medication. Or you are already on levothyroxine and wondering whether your thyroid is now well-controlled. Or your doctor has ordered a "thyroid profile" and the report shows TSH, T3, T4, Free T3, Free T4 — and you are not sure what each number means or which one matters most. The Thyroid Function Test (TFT), also called Thyroid Profile, is one of the most commonly ordered blood tests in India — yet the results are among the most frequently misinterpreted, generating unnecessary anxiety or, conversely, missing significant abnormalities. India has an extraordinarily high thyroid disease burden: an estimated 42 million Indians have thyroid disease, making it the second most common endocrine disorder after diabetes. Women are affected 5–10 times more commonly than men. This guide explains every parameter in the TFT clearly — what each test measures, the correct normal ranges, and exactly how to interpret your result.
For the free thyroid profile (FT3, FT4) specifically, see our Free Thyroid Profile guide. For thyroid antibodies (Anti-TPO) see our Anti-TPO guide. For reading lab reports generally, see our beginner's guide.
Routine check में TSH 8.4 mIU/L flagged — hypothyroidism है? Medication चाहिए? Or already levothyroxine पर हैं — thyroid well-controlled है? TFT report में TSH, T3, T4, Free T3, Free T4 — कौन सा number matters? India में estimated 42 million लोगों को thyroid disease — second most common endocrine disorder। Women 5–10× more commonly affected। यह guide सब clearly explain करती है।Table of Contents / विषय सूची
- How the Thyroid Works / थायरॉइड कैसे काम करता है?
- What Each TFT Parameter Measures
- Normal Range — TSH, T3, T4, FT3, FT4
- Hypothyroidism — High TSH, Low T3/T4
- Hyperthyroidism — Low TSH, High T3/T4
- TFT While on Thyroid Medication
- India Context — Iodine, Autoimmunity & Women's Health
- Test Preparation Checklist / टेस्ट की तैयारी
- Frequently Asked Questions / अक्सर पूछे जाने वाले सवाल
How the Thyroid Works / थायरॉइड कैसे काम करता है?
The thyroid gland produces two hormones: T4 (thyroxine — the storage and transport form, with 4 iodine atoms) and T3 (triiodothyronine — the biologically active form, with 3 iodine atoms). T4 is produced by the thyroid in much larger quantities but is relatively inactive — it is converted to the active T3 in peripheral tissues (liver, kidney, muscle) by deiodinase enzymes. The pituitary gland produces TSH (Thyroid Stimulating Hormone) to regulate thyroid output: high TSH stimulates more T3/T4 production; low TSH signals the thyroid to reduce output.
Thyroid gland दो hormones produce करती है: T4 (thyroxine — 4 iodine atoms, storage/transport form) और T3 (triiodothyronine — 3 iodine atoms, biologically active form)। Thyroid T4 much more produce करती है — peripheral tissues (liver, kidney, muscle) में T4 → T3 convert। Pituitary TSH produce करती है regulate करने के लिए: high TSH → more T3/T4। Low TSH → thyroid output reduce।- The vast majority of T3 and T4 in the blood (99%+) is bound to carrier proteins — primarily TBG (Thyroid Binding Globulin), transthyretin, and albumin. Only the small "free" fraction (Free T3, Free T4) is biologically active — it is the unbound hormone that enters cells and exerts metabolic effects.
- Total T3 and Total T4 measure both bound and free hormone together. They are significantly affected by changes in TBG concentration — which is raised by oestrogen (pregnancy, oral contraceptive pills) and lowered by androgens, steroids, and severe illness. A pregnant woman has high TBG and therefore high Total T4 — even though her free (active) T4 may be normal.
- Free T3 (FT3) and Free T4 (FT4) measure only the biologically active unbound fraction — they are not affected by TBG changes and are therefore more accurate and clinically useful in most situations. Modern thyroid panels almost always use FT3 and FT4 rather than Total T3/T4.
- The practical hierarchy: TSH is the first-line screening test. If TSH is abnormal, FT4 is added to confirm and classify the abnormality. FT3 is added when hyperthyroidism is suspected (FT3 rises before FT4 in early Graves' disease) or when T3 toxicosis is suspected.
What Each TFT Parameter Measures
TSH is produced by the pituitary gland and is the most sensitive and important single thyroid test. It has an inverse relationship with thyroid hormones — when T3/T4 are low, TSH rises; when T3/T4 are high, TSH falls. TSH changes before T3/T4 change in early thyroid disease — making it the most sensitive early marker. TSH is the recommended test for: thyroid screening in adults; monitoring levothyroxine therapy; neonatal thyroid screening (congenital hypothyroidism); pregnancy thyroid surveillance. TSH is not reliable as the sole marker when: pituitary disease is present (secondary hypothyroidism — TSH may be inappropriately normal or low despite hypothyroidism); very early onset thyroid disease before TSH has had time to respond; and during acute non-thyroidal illness (sick euthyroid syndrome — TSH can be transiently abnormal in any severe illness).
TSH: pituitary produce करती है। Thyroid hormones से inverse relationship: T3/T4 low → TSH rise; T3/T4 high → TSH fall। T3/T4 से पहले change → most sensitive early marker। Uses: thyroid screening, levothyroxine monitoring, neonatal screening, pregnancy surveillance। Not reliable when: pituitary disease (secondary hypothyroidism), very early disease, acute severe illness (sick euthyroid syndrome)।T4 (thyroxine) is the primary thyroid hormone secreted by the thyroid gland — produced in much larger quantities than T3. It is the storage and transport form of thyroid hormone, converted to the active T3 in peripheral tissues. FT4 (Free T4 / Free Thyroxine) is the small unbound biologically available fraction. FT4 is used clinically to: confirm hypothyroidism (low FT4 with high TSH = primary hypothyroidism confirmed); assess severity of hypothyroidism (lower FT4 = more severe deficiency); distinguish primary from secondary hypothyroidism (low FT4 with low/normal TSH = pituitary cause — secondary hypothyroidism); and to confirm hyperthyroidism (elevated FT4 with suppressed TSH). During levothyroxine (T4 replacement) therapy, FT4 should be within the normal range — not elevated (over-replacement) or low (under-replacement).
T4/FT4: thyroid का primary secretion, peripheral tissues में T3 convert। FT4 clinically: hypothyroidism confirm (low FT4 + high TSH = primary hypothyroid)। Severity assess (lower FT4 = more severe)। Primary vs secondary hypothyroid distinguish (low FT4 + low/normal TSH = pituitary cause)। Hyperthyroidism confirm (elevated FT4 + suppressed TSH)। Levothyroxine therapy पर: FT4 normal range में होनी चाहिए।T3 (triiodothyronine) is the biologically active thyroid hormone — it binds to nuclear thyroid hormone receptors in cells and directly drives metabolic effects. Most T3 (approximately 80%) comes from peripheral conversion of T4, and only 20% from direct thyroid secretion. FT3 (Free T3) is the unbound biologically active fraction. FT3 is particularly important in: hyperthyroidism diagnosis (FT3 is the first to rise in early Graves' disease and in T3 toxicosis — a condition where FT3 is elevated with FT4 normal, seen in toxic nodular goitre); thyroid cancer monitoring; and assessing thyroid hormone action in tissues. In hypothyroidism management, FT3 is less commonly used because T4 replacement (levothyroxine) is converted to T3 peripherally — a normal FT4 on levothyroxine typically ensures adequate T3 production.
T3/FT3: biologically active form — nuclear receptors से bind, direct metabolic effects। 80% = peripheral T4 conversion, 20% direct thyroid secretion। FT3 important: hyperthyroidism diagnosis (early Graves' में first rise, T3 toxicosis में FT3 high + FT4 normal)। Thyroid cancer monitoring। Hypothyroidism management में less commonly used (levothyroxine T4 → T3 peripherally convert)।TSH alone is adequate for: routine thyroid screening in asymptomatic adults; monitoring stable hypothyroid patients on a fixed levothyroxine dose; postpartum thyroid screening. Add FT4 when TSH is abnormal (to confirm and classify), when pituitary disease is suspected, or in pregnancy. Add FT3 when: hyperthyroidism is suspected clinically but TSH is suppressed with only mildly elevated FT4 (T3 toxicosis); in thyroid cancer surveillance; and in the immediate post-treatment period for hyperthyroidism. Many Indian labs automatically run the full panel (TSH + FT3 + FT4) as the "thyroid profile" — this is clinically acceptable but adds cost without additional diagnostic value in straightforward monitoring situations where TSH alone is sufficient.
TSH alone adequate: routine screening, stable hypothyroid monitoring, postpartum। FT4 add when: TSH abnormal, pituitary disease suspect, pregnancy। FT3 add when: T3 toxicosis suspect (TSH suppressed, only mildly elevated FT4), thyroid cancer surveillance, post-hyperthyroidism treatment। Indian labs में full panel (TSH + FT3 + FT4) = "thyroid profile" — acceptable लेकिन straightforward monitoring में TSH alone sufficient।Normal Range — TSH, T3, T4, FT3, FT4
*Reference ranges vary between labs and assay platforms. Always use the reference range printed on your specific lab report. The values below represent the most widely used reference ranges in Indian NABL-accredited labs. Units: TSH in mIU/L (= µIU/mL); T3 in ng/dL; FT3 in pg/mL; T4 in µg/dL; FT4 in ng/dL.
| Parameter | Normal Range | Hypothyroid Pattern | Hyperthyroid Pattern | Clinical Notes |
|---|---|---|---|---|
| TSH | 0.4–4.0 mIU/L Pregnancy: 0.1–2.5 (1st trimester) / 0.2–3.0 (2nd) / 0.3–3.0 (3rd) |
High (>4.0) Subclinical: 4.0–10. Overt: >10 |
Low (<0.4) Subclinical: 0.1–0.4. Overt: <0.1 |
Most important single parameter. Inverse relationship with T3/T4. Rises before T3/T4 fall in early hypothyroidism. Pregnancy has separate trimester-specific ranges. |
| FT4 | 0.8–1.8 ng/dL | Low (<0.8) | High (>1.8) | More reliable than Total T4. Not affected by TBG changes (pregnancy, OCP). First add-on when TSH is abnormal. |
| FT3 | 2.3–4.2 pg/mL | Low (<2.3) | High (>4.2) FT3 rises earlier than FT4 in Graves' |
Biologically active form. Important for hyperthyroidism diagnosis. T3 toxicosis: FT3 elevated, FT4 normal, TSH suppressed. |
| Total T4 | 5.0–12.0 µg/dL | Low | High | Less reliable than FT4 — affected by TBG changes. Falsely elevated in pregnancy and on OCP. FT4 preferred in modern labs. |
| Total T3 | 80–200 ng/dL | Low | High | Less reliable than FT3. Falls in severe illness (sick euthyroid syndrome) independently of true thyroid status. FT3 preferred in modern labs. |
- TSH has a log-linear relationship — small TSH changes mean large hormone changes: TSH does not change proportionally to thyroid hormone. A TSH rise from 1.0 to 4.0 (still within normal range) represents a meaningful reduction in thyroid hormone. A TSH of 8.0 does not mean twice as much deficiency as a TSH of 4.0 — it means several times more because the relationship is logarithmic. This is why the clinical significance of a TSH of 6.0 vs 20.0 cannot be judged by simple arithmetic.
- Biotin interference — the most common cause of spurious thyroid results in India: High-dose biotin (Vitamin B7) supplements — widely taken in India for hair fall, nail growth, and skin health — cause false results on many immunoassay-based thyroid platforms: falsely LOW TSH and falsely HIGH FT4, mimicking overt hyperthyroidism; OR falsely HIGH TSH and falsely LOW FT4, mimicking hypothyroidism. Stop all biotin-containing supplements for at least 48–72 hours (ideally 5–7 days) before any thyroid test.
- Reference ranges differ between assay platforms — never compare values across labs: A TSH of 2.8 on one platform may be equivalent to a TSH of 3.5 on another. For serial thyroid monitoring (on medication), always use the same NABL lab and the same assay platform for meaningful trend comparison.
- Sick euthyroid syndrome: Any severe acute illness (infection, MI, surgery, hospitalisation) can transiently suppress TSH and lower Total T3 — a phenomenon called sick euthyroid syndrome or non-thyroidal illness syndrome. This does not represent true thyroid disease and should not be treated with thyroid medication. Avoid routine thyroid testing during acute illness unless thyroid disease is specifically suspected.
Hypothyroidism — High TSH, Low T3/T4
Subclinical hypothyroidism is defined as TSH elevated above the upper limit of normal (4.0 mIU/L) with FT4 still within the normal range. It is extremely common in India — particularly in women above 35. The decision to treat is individualised:
- Treat if: TSH above 10 (regardless of symptoms); TSH 4–10 with symptoms of hypothyroidism; TSH 4–10 in pregnancy (lower TSH target in pregnancy); TSH 4–10 with positive Anti-TPO antibodies (higher risk of progression to overt hypothyroidism — approximately 5% per year); TSH 4–10 with infertility or recurrent miscarriage.
- Watch and wait if: TSH 4–10 in an asymptomatic elderly person (TSH naturally rises slightly with age — the upper limit of normal is higher in people above 70); TSH mildly elevated in a single test without confirmation on repeat.
- Always confirm on repeat: A single mildly elevated TSH (4–7 mIU/L) should be confirmed on a repeat test 4–6 weeks later, as transient TSH elevations occur in convalescence from illness, stress, and other non-thyroidal causes. Treat on two confirmed elevated TSH measurements, not one.
Overt hypothyroidism (TSH above 10 mIU/L with FT4 below normal) requires treatment with levothyroxine in virtually all patients regardless of symptoms — the cardiovascular and metabolic consequences of sustained overt hypothyroidism (dyslipidaemia, atherosclerosis acceleration, hypertension, heart failure) make treatment essential. Treatment: oral levothyroxine (L-T4) sodium — taken once daily on an empty stomach, 30–60 minutes before breakfast. Dose: 1.6 µg/kg/day as a starting estimate, adjusted based on TSH monitoring every 6–8 weeks until target TSH is reached (typically 0.5–2.5 mIU/L for most adults; lower target in pregnancy). In elderly patients and those with cardiac disease, start with a very low dose (25–50 µg/day) and titrate up slowly — rapid correction of longstanding hypothyroidism can precipitate cardiac events.
Overt hypothyroidism: TSH >10 + FT4 below normal → virtually all patients में levothyroxine ज़रूरी। Treatment: Oral levothyroxine (L-T4), empty stomach पर, breakfast से 30–60 minutes पहले। Dose: 1.6 µg/kg/day starting, TSH monitoring 6–8 weeks → target TSH 0.5–2.5 mIU/L। Elderly/cardiac disease: very low starting dose (25–50 µg/day) → slowly titrate — rapid correction = cardiac events precipitate।- Hashimoto's thyroiditis (autoimmune): The most common cause of hypothyroidism globally and in India. The immune system produces antibodies (Anti-TPO, Anti-TG) that attack thyroid tissue → gradual thyroid destruction → progressive hypothyroidism. Strongly associated with family history of autoimmune disease. See our Anti-TPO guide.
- Iodine deficiency: India has a significant iodine deficiency problem in inland, non-coastal, and mountainous regions (Himalayan belt, northeastern states, central and eastern India). Iodine is required for T3 and T4 synthesis — deficiency reduces thyroid hormone production. Universal salt iodisation has dramatically reduced this in urban areas, but rural inland areas remain at risk.
- Post-thyroidectomy: Surgical removal of the thyroid (for thyroid cancer, large goitre, or severe hyperthyroidism) causes permanent hypothyroidism requiring lifelong levothyroxine replacement.
- Post-radioiodine: Radioiodine therapy (I-131) for hyperthyroidism or thyroid cancer frequently causes subsequent hypothyroidism.
- Post-partum thyroiditis: Transient autoimmune thyroiditis occurring within 12 months of delivery — typically a phase of hyperthyroidism followed by hypothyroidism, then resolution in most women. Affects 5–10% of Indian women post-delivery.
- Medications: Amiodarone (cardiac drug), lithium (psychiatric), interferon-alpha, some checkpoint inhibitors — all can induce hypothyroidism.
Hyperthyroidism — Low TSH, High T3/T4
- Overt hyperthyroidism: TSH below 0.1 mIU/L (suppressed) + elevated FT4 (and/or FT3). Symptoms: weight loss despite good/increased appetite, heat intolerance, excessive sweating, palpitations, rapid heart rate (sinus tachycardia or atrial fibrillation), anxiety, tremor, diarrhoea, light or absent periods in women, eye changes (exophthalmos — protruding eyes, in Graves' disease specifically). Treatment: antithyroid drugs (carbimazole or propylthiouracil — PTU), radioiodine therapy, or thyroidectomy — under endocrinologist supervision.
- Subclinical hyperthyroidism: TSH 0.1–0.4 mIU/L (low but not fully suppressed) with FT4 and FT3 within the normal range. Often asymptomatic. Clinical significance: increased risk of atrial fibrillation (particularly in patients above 60) and bone mineral density loss (osteoporosis risk, particularly in post-menopausal women). Treatment decision individualised based on age, cardiac status, bone density, and cause.
- T3 toxicosis: TSH suppressed + FT3 elevated + FT4 normal. Seen in toxic nodular goitre (where autonomous thyroid nodules preferentially produce T3). Diagnosed by measuring FT3 alongside TSH — missed if only FT4 is measured.
- Causes in India: Graves' disease (most common — autoimmune, TSH receptor antibodies, usually with goitre and eye changes); toxic multinodular goitre (multiple autonomously functioning nodules — common in iodine-deficient endemic goitre areas); solitary toxic adenoma; and amiodarone-induced thyrotoxicosis (Amiodarone, widely used for cardiac arrhythmias in India, contains 37% iodine by weight and can induce either hypothyroidism or hyperthyroidism).
TFT While on Thyroid Medication
Levothyroxine is the standard treatment for hypothyroidism — it is synthetic T4. Key monitoring rules:
- When to test: Check TSH 6–8 weeks after starting levothyroxine or after any dose change — it takes 6–8 weeks for TSH to fully reflect a new dose. Testing too early (within the first 4 weeks) gives a misleadingly abnormal TSH.
- Target TSH on levothyroxine: For most adults with hypothyroidism: 0.5–2.5 mIU/L. For pregnancy: trimester-specific lower targets (0.1–2.5 in first trimester). For thyroid cancer post-thyroidectomy: suppressed TSH target (below 0.1) for high-risk cancer, 0.5–1.0 for low-risk cancer.
- Do NOT take your morning levothyroxine before the blood draw: Levothyroxine causes a transient post-dose spike in FT4 for 6–8 hours after the dose. If you take your tablet, then go to the lab, your FT4 will appear falsely elevated — suggesting over-replacement when you are actually well-dosed. Always draw blood first, then take the morning tablet.
- Once-daily dosing: Levothyroxine should be taken first thing in the morning, 30–60 minutes before breakfast, with a full glass of water. Calcium supplements, iron supplements, antacids, coffee, and soy products significantly reduce levothyroxine absorption — separate by at least 4 hours from levothyroxine intake.
- Once stable, monitor annually: When TSH is within target range on a stable dose, annual monitoring is adequate for most patients. More frequent monitoring (every 3–6 months) is needed: during pregnancy; after any dose change; if new medications are started that affect levothyroxine absorption; and in elderly patients.
For patients being treated for hyperthyroidism with carbimazole (most commonly used in India) or propylthiouracil (PTU — preferred in pregnancy):
- Monitor FT4 and FT3 alongside TSH — TSH may remain suppressed for weeks to months even after FT4 has normalised, because the pituitary recovers slowly. Do not adjust carbimazole dose based on TSH alone in the early treatment period — use FT4 as the primary guide in the first 3–6 months.
- After 12–18 months of antithyroid treatment, TSH receptor antibodies (TRAb or TSI) should be checked to assess remission likelihood before stopping carbimazole.
- CBC must be checked periodically during carbimazole therapy — agranulocytosis (dangerous fall in white blood cells) is a rare but serious complication. Any patient on carbimazole who develops a fever or sore throat should urgently check a CBC and stop carbimazole pending the result.
India Context — Iodine, Autoimmunity & Women's Health
India's iodine deficiency problem is geographically concentrated but significant: the Himalayan and sub-Himalayan belt (Uttarakhand, Himachal Pradesh, J&K, northeastern states), the Gangetic plain (particularly eastern UP, Bihar), and central and eastern India have historically had high rates of iodine deficiency. India's universal salt iodisation programme has substantially reduced the burden in urban areas — but rural inland populations, populations that consume non-iodised rock salt (sendha namak — widely used for religious purposes and in rural areas), and populations dependent on groundwater with low iodine content remain at risk. Iodine deficiency causes: goitre (enlarged thyroid — the thyroid enlarges to compensate for iodine shortage), hypothyroidism, and in pregnancy, cretinism (severe intellectual disability in the newborn from severe prenatal iodine deficiency). All Indian households should use iodised salt (double-fortified salt with iron and iodine is now available). Patients on very low-sodium diets for hypertension or heart failure should discuss iodine supplementation with their physician.
India में iodine deficiency: Himalayan belt (Uttarakhand, HP, J&K, northeast), Gangetic plain (eastern UP, Bihar), central/eastern India। Universal salt iodisation = urban में substantially reduce। Rural inland, sendha namak (non-iodised rock salt — religious/rural use), low-iodine groundwater = still at risk। Causes: goitre, hypothyroidism, cretinism (pregnancy में severe deficiency → newborn intellectual disability)। Iodised salt use करें। Low-sodium diet पर: physician से iodine supplementation discuss।Thyroid disease in Indian women deserves special clinical attention because of the unique interaction between thyroid function and women's reproductive health:
- PCOS and hypothyroidism: Both are extremely common in Indian women and present with overlapping symptoms (irregular periods, weight gain, fatigue, hair loss). TSH is mandatory in any Indian woman evaluated for PCOS — hypothyroidism causes or worsens PCOS-like features, and treating hypothyroidism often improves menstrual regularity independently of PCOS management. See our Female Hormones guide.
- Thyroid in pregnancy: Hypothyroidism in pregnancy — even subclinical (TSH 2.5–10 with normal FT4) — is associated with impaired foetal brain development, miscarriage, preterm birth, and low birth weight. TSH should be tested at the first antenatal visit in all Indian pregnant women. Trimester-specific TSH targets are lower than non-pregnancy targets. Levothyroxine dose typically needs to be increased by 25–50% in pregnancy.
- Post-partum thyroiditis: Transient autoimmune thyroiditis occurring in 5–10% of Indian women within 12 months of delivery. Classic pattern: hyperthyroid phase (1–4 months post-delivery) → hypothyroid phase (4–8 months) → resolution in most (but 20–30% develop permanent hypothyroidism). Any Indian woman with symptoms of thyroid dysfunction in the first year after delivery should have TSH checked.
- Menopause and thyroid: Hypothyroidism and perimenopausal symptoms overlap significantly — fatigue, weight gain, mood changes, irregular periods, sleep disturbance. TSH is essential in any perimenopausal Indian woman with these symptoms to avoid attributing truly treatable hypothyroidism to menopause.
Test Preparation Checklist / टेस्ट की तैयारी
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Stop all biotin (Vitamin B7) supplements at least 48–72 hours before the test — ideally 5–7 days. This is the single most important preparation step for thyroid testing in India. Biotin is present in: hair fall supplements (most contain 5,000–10,000 µg biotin); multivitamins; standalone biotin tablets (5,000 µg and 10,000 µg biotin tablets are widely sold in India over the counter); and some B-complex formulations. Even standard B-complex supplements containing 30–300 µg biotin can interfere with some sensitive assay platforms. When in doubt, stop all supplements for 5–7 days. Tell your doctor if you have been taking biotin — results should be repeated after an adequate biotin-free period if spurious results are suspected.
Biotin (Vitamin B7) supplements: test से कम से कम 48–72 hours (ideally 5–7 days) पहले stop। Most important step। Biotin in: hair fall supplements (most में 5,000–10,000 µg), multivitamins, standalone biotin tablets, B-complex। Doubt होने पर 5–7 days सब stop करें। Doctor को बताएं — spurious results suspect होने पर biotin-free period बाद repeat। -
If you are on levothyroxine: do NOT take your morning tablet before the blood draw. Take the blood sample first, then take your morning levothyroxine after leaving the lab. This is the correct protocol for monitoring levothyroxine therapy. If you accidentally took your morning dose before the blood draw, inform the lab and your doctor — the FT4 result may be falsely elevated and the test may need to be repeated.
Levothyroxine पर हैं: morning tablet blood draw से PEHLE नहीं। Blood sample पहले → lab से निकलने के बाद levothyroxine लें। Accidentally morning dose ले लिया → lab और doctor को inform — FT4 falsely elevated हो सकता है, repeat needed। -
Fasting is not strictly required for thyroid tests — but an 8–12 hour fast is recommended. Thyroid hormones (TSH, T3, T4) are not significantly affected by acute food intake. However, because thyroid tests are commonly ordered as part of a broader panel including fasting blood glucose and lipid profile, and because a morning fasting draw provides the most standardised baseline TSH (TSH has mild diurnal variation — slightly higher in the early morning), an overnight fast is the recommended standard. The most important thing is to consistently test at the same time of day (morning) for serial monitoring.
Fasting strictly required नहीं — लेकिन 8–12 hours fast recommended। Thyroid hormones food से significantly affect नहीं। Broader panel (glucose, lipids) के साथ order होती है — overnight fast standard। TSH mild diurnal variation (morning slightly higher) → morning draw most standardised। Serial monitoring: consistently same time of day। -
Disclose all current medications — several drugs significantly affect thyroid hormone levels and test results. Important medications affecting TFT: iodine-containing drugs — amiodarone (markedly affects thyroid in both directions); contrast agents used in CT scans and angiograms (transiently suppress TSH); lithium, interferon-alpha, checkpoint inhibitors (can induce hypothyroidism); oestrogen and OCP (raise TBG → raise Total T4, not FT4); heparin (transiently elevates FT4 — artifact); and high-dose steroids (transiently suppress TSH).
Medications disclose करें: Amiodarone (markedly affect — both directions)। CT contrast (TSH transiently suppress)। Lithium, interferon, checkpoint inhibitors (hypothyroidism induce)। Oestrogen/OCP (TBG raise → Total T4 high, not FT4)। Heparin (FT4 transient artifact elevate)। High-dose steroids (TSH transiently suppress)। -
Always use the same NABL-accredited lab for serial monitoring on levothyroxine. TSH values can differ by 20–30% between different assay platforms. If you switch labs, an apparent TSH change may reflect an assay difference rather than a true change in thyroid status — leading to unnecessary dose adjustments. Establish one lab for long-term thyroid monitoring and stick with it. Note the assay platform on your report (Roche Cobas, Abbott Architect, Siemens ADVIA — each has slightly different normal ranges and values).
Serial monitoring: same NABL lab use करें। TSH values different assay platforms में 20–30% differ। Lab switch = apparent TSH change (assay difference नहीं true change) → unnecessary dose adjustment। One lab establish → long-term stick। Assay platform note करें (Roche Cobas, Abbott Architect, Siemens ADVIA — slightly different ranges)। -
Avoid testing during acute illness (fever, infection, hospitalisation) unless thyroid disease is specifically suspected. Any severe acute illness causes sick euthyroid syndrome — transiently suppressed TSH, low Total T3, and sometimes mildly abnormal FT4 — without any true underlying thyroid disease. Thyroid test results during acute illness are unreliable and should not be used as the basis for thyroid medication decisions. If thyroid disease is specifically suspected (e.g., thyroid storm in a critically ill patient), testing is appropriate — but results must be interpreted with this caveat in mind.
Acute illness (fever, infection, hospitalisation) के दौरान test avoid — unless thyroid disease specifically suspect। Sick euthyroid syndrome: TSH transiently suppress, Total T3 low, FT4 mildly abnormal — no true thyroid disease। Acute illness में results unreliable → medication decisions का basis नहीं। Thyroid storm suspect → testing appropriate लेकिन caveat के साथ interpret।
✅ Book Thyroid Function Test (TSH + FT3 + FT4) — Home Collection Available
For thyroid screening: TSH alone is adequate. For confirmed thyroid disease or abnormal TSH: book the complete profile (TSH + FT3 + FT4). 8–12 hours fast recommended. Stop biotin supplements 48–72 hours before. If on levothyroxine: draw blood before morning dose. Always use the same NABL lab for serial monitoring:
Affiliate link: I may earn a small commission at no extra cost to you. TFT is available at government hospitals and PMJAY-empanelled facilities across India. Always have TFT results interpreted by a qualified physician or endocrinologist — thyroid medication decisions require clinical context (symptoms, physical examination, medication history, pregnancy status) alongside lab values. Never adjust levothyroxine dose based on a single test result without doctor guidance.
TFT government hospitals में available। TSH alone screening के लिए adequate। Confirmed disease या abnormal TSH: complete profile (TSH + FT3 + FT4)। Biotin 48–72 hours stop। Levothyroxine: blood draw morning dose से PEHLE। Same NABL lab serial monitoring। Physician से symptoms + history + lab values के साथ interpret।Thyroid Health Support & Medication Management
Two products relevant to thyroid health management — a selenium-zinc-vitamin C-E micronutrient supplement (selenium is an essential cofactor for the deiodinase enzymes that convert T4 to active T3, and is required for thyroid peroxidase — deficiency is associated with autoimmune thyroid disease and is common in parts of India) and a weekly pill organiser (essential for patients on daily levothyroxine, which must be taken consistently at the same time each morning — missing doses or inconsistent timing is the most common cause of inadequate TSH control in Indian patients on thyroid medication). These products support thyroid health and medication compliance — they do not treat thyroid disease. Never start, stop, or adjust levothyroxine or antithyroid medications without your endocrinologist or physician's guidance. Selenium supplements should not be taken in doses above 200 µg/day — excess selenium is toxic.
Selenium is a trace mineral with a critical and often underappreciated role in thyroid physiology. The thyroid gland contains the highest selenium concentration of any organ in the body — selenium is an essential component of the deiodinase enzymes (particularly Type 1 and Type 2 deiodinase, DIO1 and DIO2) that convert the relatively inactive T4 to the biologically active T3 in peripheral tissues and within the thyroid gland itself. Without adequate selenium, this T4→T3 conversion is impaired — potentially contributing to symptoms of hypothyroidism even when TSH and T4 appear adequate. Selenium is also an essential cofactor for glutathione peroxidase, the primary antioxidant enzyme protecting thyroid cells from hydrogen peroxide — a by-product of thyroid hormone synthesis that accumulates in the thyroid at high concentrations. Insufficient selenium → inadequate GPx activity → hydrogen peroxide accumulation → oxidative thyroid cell damage → may contribute to autoimmune thyroid disease initiation and progression. The clinical evidence: multiple randomised controlled trials (particularly in Hashimoto's thyroiditis patients) have demonstrated that selenium supplementation at 80–200 µg/day significantly reduces anti-TPO antibody titres over 3–6 months and improves thyroid ultrasound echotexture — suggesting a genuine immunomodulatory and antioxidant benefit in autoimmune thyroid disease. A 2021 systematic review (Ventura et al.) of 12 RCTs found selenium supplementation significantly reduced Anti-TPO antibody levels in Hashimoto's thyroiditis. The Forest Harvest formulation provides 40 µg elemental selenium (as organic selenium — selenomethionine form, better absorbed than inorganic selenite) alongside zinc (essential for T3-nuclear receptor binding), Vitamin C (regenerates Vitamin E; antioxidant synergy), and Vitamin E (protects thyroid cell membranes). Important safety note: selenium toxicity (selenosis) occurs at doses above 400 µg/day. Never exceed 200 µg/day total selenium from all sources. This 40 µg dose is safe for supplementation. Selenium supplementation does not replace levothyroxine therapy for confirmed hypothyroidism — it is a complementary micronutrient support for thyroid health.
Selenium: thyroid में highest concentration। Deiodinase enzymes (DIO1, DIO2) का essential component — T4 → T3 conversion। Without adequate selenium: T4→T3 conversion impaired। Glutathione peroxidase (GPx) cofactor: thyroid cell को H₂O₂ से protect। Selenium deficiency → GPx low → oxidative damage → autoimmune thyroid disease। RCTs (12 trials, Ventura 2021): 80–200 µg/day → Anti-TPO antibody titres significantly reduce (Hashimoto's में)। Forest Harvest: 40 µg organic selenium (selenomethionine — better absorbed) + Zinc (T3 receptor binding) + Vitamin C + Vitamin E। Safety: selenosis >400 µg/day। Never >200 µg/day। Levothyroxine replace नहीं करता — complementary support। View on Amazon IndiaAffiliate link — small commission at no extra cost.
For the estimated 10–15 million Indians currently taking daily levothyroxine, medication adherence is the single most important and most commonly inadequate determinant of thyroid control. Levothyroxine has a long half-life (approximately 7 days) — which means missing one or two doses per week has a relatively modest acute effect on thyroid hormone levels, but chronically inconsistent dosing produces unpredictable TSH fluctuations that make dose optimisation extremely difficult. The most common reasons for inadequate TSH control in Indian hypothyroid patients on levothyroxine: forgotten doses (the most common — particularly relevant because levothyroxine must be taken first thing in the morning, often before the routine of the day has begun and before breakfast, which is a cognitively demanding time for medication adherence); incorrect timing (taking it with breakfast or coffee, which reduces absorption by 25–40%); and dose interaction with other morning medications (calcium, iron, antacids — which should be taken at least 4 hours after levothyroxine). A weekly pill organiser addresses all of these simultaneously: it makes it immediately obvious whether the day's tablet has been taken (eliminating "did I take my tablet?" uncertainty which leads to double-dosing or missed doses); it can be filled once per week, reducing the daily cognitive burden; and it creates a visual routine cue that supports consistent morning timing. The PharmEasy 7-day pill box has seven clearly labelled compartments with easy-open lids appropriate for daily use by adults of all ages. For patients on multiple medications (a very common scenario in hypothyroid Indian patients who frequently also have diabetes, hypertension, and dyslipidaemia), the organiser helps manage the complex timing requirements of levothyroxine relative to other medications. Note: a pill organiser is a medication management tool — it does not replace professional medical guidance for thyroid medication dosing. Never change your levothyroxine dose without consulting your physician.
10–15 million Indians daily levothyroxine पर। Medication adherence = most important + most commonly inadequate determinant of thyroid control। Levothyroxine half-life ~7 days → 1–2 doses miss करना = acute modest effect, लेकिन chronically inconsistent = unpredictable TSH fluctuations → dose optimisation difficult। Common reasons poor control: forgotten doses (morning, cognitively demanding time); incorrect timing (breakfast/coffee के साथ → 25–40% absorption reduce); interaction with calcium/iron/antacids (4 hours separate ज़रूरी)। Weekly pill organiser: daily tablet taken है या नहीं immediately obvious। Weekly fill = daily cognitive burden कम। Visual routine cue। PharmEasy 7-day: 7 labelled compartments, easy-open lids। Multiple medications (DM, HTN, dyslipidaemia common in hypothyroid patients) → complex timing management। Medical guidance replace नहीं करता। View on Amazon IndiaAffiliate link — small commission at no extra cost.
Related Tests / संबंधित जांचें
These tests are commonly ordered alongside TFT for complete thyroid and metabolic evaluation:
TFT के साथ ये जांचें complete thyroid और metabolic evaluation में order होती हैं:Frequently Asked Questions / अक्सर पूछे जाने वाले सवाल
A TSH of 6.5 mIU/L (assuming your lab's upper limit of normal is 4.0 mIU/L) is in the subclinical hypothyroidism range — TSH above normal but with FT4 still within the normal range. Whether you need levothyroxine depends on multiple factors that your physician will assess: Do you have symptoms of hypothyroidism (fatigue, weight gain, cold intolerance, constipation, dry skin, hair loss, slow heart rate)? Is your Anti-TPO antibody positive (if so, risk of progression to overt hypothyroidism is higher)? Are you pregnant or planning to be (in which case treatment is generally recommended even for subclinical hypothyroidism to protect foetal brain development)? Do you have infertility or recurrent miscarriage? Are you elderly (above 70 — where mild TSH elevation may be age-appropriate and not require treatment)? Before any treatment decision, the TSH should be confirmed on a repeat test 4–6 weeks later — a single mildly elevated TSH can reflect transient non-thyroidal causes. Never start levothyroxine based on a single TSH value without doctor guidance.
उत्तर: TSH 6.5 = subclinical hypothyroidism (TSH high, FT4 normal)। Levothyroxine decision factors: Symptoms हैं? Anti-TPO positive? Pregnant/planning? Infertility/miscarriage? Elderly (>70 — mild TSH elevation age-appropriate)?। Confirm on repeat test 4–6 weeks बाद — single mild elevation = transient cause। Single TSH value पर never levothyroxine — doctor guidance।Total T3 and Total T4 measure all the thyroid hormone in the blood — both the large fraction that is bound to carrier proteins (TBG, albumin, transthyretin) and the small free fraction. The bound hormone is inactive — it is a storage and transport form that cannot enter cells. Only the "free" or unbound fraction (Free T3, Free T4) is biologically active and actually drives metabolic effects. The key clinical problem with Total T3/T4: they are significantly affected by changes in TBG (the main carrier protein). Oestrogen (from pregnancy or oral contraceptive pills) raises TBG → raises Total T4 — even though Free T4 is normal and thyroid function is adequate. This makes Total T4 falsely elevated in pregnant women and those on the OCP. Free T3 and Free T4 are not affected by TBG changes and give a more accurate picture of true thyroid hormone activity. Modern labs use FT3 and FT4 for this reason — if your older report shows Total T3/T4, the normal ranges are different from Free T3/T4 ranges.
उत्तर: Total T3/T4: bound (inactive, storage/transport) + free (active) दोनों measure। TBG changes से affected: pregnancy/OCP → TBG high → Total T4 falsely high (Free T4 normal)। FT3/FT4: only unbound active fraction। TBG changes से independent → more accurate। Modern labs FT3/FT4 use। Older report में Total T3/T4 है → reference ranges different। Pregnancy/OCP पर हैं → Total T4 meaningfully interpret नहीं — FT4 use।Yes — this is one of the most important and most commonly overlooked causes of spurious thyroid test results in India. High-dose biotin (Vitamin B7) — which is present in most hair fall supplements sold in India, typically at doses of 5,000–10,000 µg (5–10 mg) per tablet — interferes with many immunoassay-based thyroid test platforms. The interference mimics either hyperthyroidism (falsely low TSH, falsely high FT4 — the most common pattern, because biotin competes with the detection system in streptavidin-based assays) or hypothyroidism (falsely high TSH, falsely low FT4 — on different platforms). A patient who has been taking biotin for hair fall, comes for a thyroid test, and is told their TSH is very low and FT4 is very high, may be incorrectly started on antithyroid drugs for apparent hyperthyroidism — when in reality they have no thyroid disease at all. The solution is simple: stop all biotin supplements for at least 48–72 hours (ideally 5–7 days) before any thyroid test. This is a mandatory pre-test instruction that every lab should ideally communicate to patients.
उत्तर: हाँ — most important and overlooked cause of spurious thyroid results in India। Hair fall supplements में 5,000–10,000 µg biotin → immunoassay platforms interfere। Most common: falsely low TSH + falsely high FT4 (hyperthyroidism mimic) → patient antithyroid drugs पर — no thyroid disease। Solution: test से 48–72 hours (ideally 5–7 days) पहले सब biotin stop। Mandatory pre-test instruction।Take your blood test first — before your morning levothyroxine tablet. After the blood draw, take your tablet as normal. This is the correct protocol. The reason: levothyroxine (T4) causes a transient rise in Free T4 in the blood for approximately 6–8 hours after each dose. If you take your morning tablet, then go to the lab, your FT4 will appear falsely elevated — potentially above the normal range — even if your actual thyroid replacement is appropriate. This can lead to an incorrect conclusion of over-replacement and an inappropriate dose reduction. TSH is not significantly affected by this post-dose spike (because TSH responds slowly to thyroid hormone changes), but FT4 is. To ensure the most accurate combined TSH + FT4 result that reflects your true steady-state thyroid status, always draw blood before the morning dose.
उत्तर: Blood test FIRST — morning levothyroxine tablet के पहले। Blood draw → phir tablet। Reason: levothyroxine post-dose FT4 spike (6–8 hours) → FT4 falsely elevated → over-replacement का incorrect conclusion → inappropriate dose reduction। TSH post-dose spike से significantly affect नहीं (slowly respond)। FT4 affect होती है। Accurate steady-state TSH + FT4: always blood draw BEFORE morning dose।Not necessarily — and not without your physician's assessment. A TSH of 0.3 mIU/L (below the lower limit of normal, typically 0.4 mIU/L) is technically in the subclinical hyperthyroid range if FT3 and FT4 are normal. However, the clinical significance depends entirely on the context. If you are on levothyroxine for hypothyroidism and your FT4 is within the normal range with FT3 also normal — a TSH of 0.3 may represent a very mild over-replacement that can be addressed with a small dose reduction, or it may be at the lower end of your individual optimal TSH (some patients feel better with a slightly lower TSH). A TSH of 0.3 in an elderly patient (above 70) is more concerning for atrial fibrillation and bone density loss than in a young adult. If you are on levothyroxine for thyroid cancer suppression — a low TSH may be the target, not something to correct. Always discuss TSH results in the full clinical context with your endocrinologist before any dose adjustment.
- American Thyroid Association (ATA) — Hypothyroidism Guidelines: ATA Guidelines for Hypothyroidism in Adults
- Indian Thyroid Society (ITS): Indian Thyroid Society — Clinical Practice Guidelines
- MedlinePlus (NIH): TSH Test — Patient Information
⚠️ Medical Disclaimer / चिकित्सा अस्वीकरण
This article is for educational purposes only. TFT results must always be interpreted by a qualified physician or endocrinologist alongside clinical symptoms, examination findings, medication history, pregnancy status, and other investigations. Never start, stop, or adjust levothyroxine or antithyroid medications based on a lab report or this guide alone. A single abnormal TSH result requires confirmation and clinical context before treatment decisions are made. Stop biotin supplements before testing. If you are pregnant and have an abnormal TFT, see an endocrinologist immediately — untreated thyroid disease in pregnancy has serious consequences for foetal brain development.
यह लेख केवल शैक्षिक उद्देश्यों के लिए है। TFT results को physician/endocrinologist से symptoms + examination + medications + pregnancy status के साथ interpret करवाएं। Levothyroxine या antithyroid medications lab report या guide के आधार पर alone start/stop/adjust नहीं। Single abnormal TSH = confirmation + clinical context पहले। Biotin supplements testing से पहले stop। Pregnancy में abnormal TFT → endocrinologist immediately।
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