Hormone Test

Thyroid Function Tests (TSH, T3, T4)

Name: Thyroid Function Tests (TSH, T3, T4): Panel, Normal Range & Results
Creator: Suman Konda
Published: 2026-07-05

Your thyroid controls your metabolism, energy and weight. Here's what TSH, T3 and T4 values in your report actually mean.¹

Written by Suman Konda, Clinical Pharmacist · Based on peer-reviewed sources · Editorial policy · Not medical advice

Last reviewed and updated: 26 September 2026 · How we check our content

Quick answer

A thyroid profile measures TSH (normally 0.4 to 4.0 mIU/L) and free T4 (normally 0.8 to 1.8 ng/dL). TSH moves in the opposite direction to thyroid hormones: high TSH with low free T4 means hypothyroidism, while low TSH with high free T4 means hyperthyroidism. A high TSH with normal free T4 is subclinical hypothyroidism, the commonest abnormal pattern.

Key points

High TSH + low free T4 = overt hypothyroidism; high TSH + normal T4 = subclinical (the commonest abnormal pattern).
TSH moves in the opposite direction to thyroid hormones.
Pregnancy needs a tighter TSH range: 0.1–2.5 mIU/L in the first trimester.

What is a thyroid test?

The thyroid is a butterfly-shaped gland in your neck that produces hormones controlling metabolism, energy, weight, heart rate and mood. A thyroid profile measures TSH (Thyroid Stimulating Hormone), T3 (Triiodothyronine) and T4 (Thyroxine) to check if your thyroid is underactive (hypothyroidism) or overactive (hyperthyroidism). Thyroid disorders, and hypothyroidism in particular, are common everywhere and affect women several times more often than men.

Scroll sideways to see the whole diagram

How TSH and free T4 combine to give a thyroid diagnosis.

What the grid shows. TSH and free T4 are interpreted together. A high TSH with a low free T4 is overt hypothyroidism; a high TSH with a normal free T4 is subclinical hypothyroidism, which is the commonest abnormal pattern and often needs monitoring rather than treatment. A low TSH with a high free T4 is overt hyperthyroidism, and a low TSH with a normal free T4 is the subclinical form. The one combination that points away from the thyroid itself is a low TSH with a low free T4, which suggests a pituitary cause. The counter-intuitive part is that a high TSH means an underactive gland, because TSH is the signal telling the thyroid to work harder.

Thyroid Normal Ranges

Test	Normal Range	Unit
TSH (Thyroid Stimulating Hormone)	0.4 – 4.0	mIU/L
Free T4 (FT4)	0.8 – 1.8	ng/dL
Free T3 (FT3)	2.3 – 4.2	pg/mL
Total T4	5.0 – 12.0	µg/dL
Total T3	80 – 200	ng/dL
TSH in Pregnancy (1st trimester)	0.1 – 2.5	mIU/L

What does HIGH TSH mean?

HIGH TSH Above 4.0 mIU/L: Hypothyroidism

High TSH means your thyroid is underactive (hypothyroidism). Your brain is sending more TSH signals trying to push a sluggish thyroid to work harder. Symptoms include weight gain, fatigue, cold intolerance, dry skin, hair loss, constipation and depression. In countries with adequate dietary iodine, autoimmune Hashimoto's thyroiditis is the most common cause. Treatment is a daily thyroid hormone tablet (levothyroxine).

What does LOW TSH mean?

LOW TSH Below 0.4 mIU/L: Hyperthyroidism

Low TSH means your thyroid is overactive (hyperthyroidism): producing too much hormone. Your brain reduces TSH because there's already excess thyroid hormone. Symptoms include weight loss despite good appetite, racing heart, sweating, anxiety, tremors and heat intolerance. Graves' disease is the most common cause. Treatment includes medications, radioactive iodine or surgery.

What does TSH mean in pregnancy?

PREGNANCY TSH target below 2.5 mIU/L

In pregnancy, normal TSH ranges are different and stricter. American Thyroid Association guidance recommends using a laboratory's own pregnancy- and trimester-specific reference range where available; where none exists, an upper limit of around 4.0 mIU/L (roughly 0.5 mIU/L below the non-pregnant upper limit) is a reasonable substitute, since a rigid 2.5 mIU/L cut-off used in earlier guidance has since been shown to over-diagnose in many populations.³ Untreated hypothyroidism in pregnancy increases risk of miscarriage, premature birth and developmental problems in the baby, so an abnormal result and the decision to treat are best worked through with the obstetric team rather than by the number alone.

Subclinical hypothyroidism

If TSH is mildly elevated (4–10 mIU/L) but T3 and T4 are normal, it's called subclinical hypothyroidism. Many people have no symptoms. Your doctor may or may not recommend treatment depending on your TSH level, symptoms, age and whether you are pregnant or planning pregnancy. Whether treating it actually helps is genuinely debated: in a placebo-controlled trial of 737 adults aged 65 and over with persisting subclinical hypothyroidism, a year of levothyroxine brought TSH down as expected but produced no measurable improvement in hypothyroid symptoms or tiredness compared with placebo.² That's why age, symptoms and the size of the TSH rise all factor into the decision rather than the abnormal number alone.

How the thyroid tests fit together

A thyroid profile usually reports TSH along with free T4 (and sometimes free T3). TSH is a pituitary hormone that tells the thyroid how hard to work, so it is exquisitely sensitive: when the thyroid is underactive, TSH rises to push it; when overactive, TSH falls.

This is why TSH is the primary screening test, with free T4 confirming the picture. A high TSH with low free T4 confirms an underactive thyroid (hypothyroidism), while a low TSH with high free T4 confirms an overactive thyroid (hyperthyroidism).

Common causes of abnormal thyroid results

The most frequent cause of an underactive thyroid is Hashimoto's thyroiditis, an autoimmune condition confirmed by thyroid antibody (anti-TPO) testing. An overactive thyroid is most often due to Graves' disease, another autoimmune condition.

Thyroid problems are far more common in women and become more likely with age, which is why testing is often done when investigating symptoms such as unexplained weight change, fatigue, cold or heat intolerance, palpitations, or changes in mood and periods.

Subclinical thyroid disease

Sometimes TSH is mildly abnormal while free T4 remains normal: called subclinical hypo- or hyperthyroidism. This does not always need treatment, and the decision depends on how abnormal the TSH is, whether antibodies are present, symptoms, age and pregnancy plans.

Because of this, a borderline thyroid result is often repeated after a few weeks rather than acted on immediately, to see whether it is a temporary fluctuation or a persistent trend.

Thyroid myths vs facts

Thyroid testing attracts more folklore than almost any other blood test. Here is what the evidence actually says:

MYTH One abnormal TSH means tablets for life.

Fact: A mildly raised TSH with a normal free T4 is subclinical hypothyroidism, and guidelines suggest rechecking in 6–12 weeks before any treatment decision. Thyroid levels wobble with illness, sleep and even time of day — one mildly raised reading is not a lifetime prescription.

MYTH Thyroid problems always show up as weight change.

Fact: Many people with thyroid dysfunction notice no weight change at all. Fatigue, feeling cold, constipation, hair changes or low mood can be the whole story — and some have no symptoms, with the abnormal TSH found incidentally.

MYTH “Natural” thyroid supplements are safer than prescribed hormone.

Fact: Unregulated thyroid supplements vary wildly in what they actually contain, and some have caused dangerous hormone excess. Prescribed levothyroxine is a precisely measured dose of the same hormone your gland makes. Discuss any supplement with your doctor before combining it with treatment.

MYTH You must fast before a thyroid test.

Fact: Fasting is not usually required. What matters more is consistency — TSH is highest in the early morning, so testing at roughly the same morning time each round gives the most comparable trend.

MYTH More iodine fixes every thyroid problem.

Fact: Most thyroid disease in India is autoimmune (Hashimoto’s, Graves’), not iodine deficiency — and excess iodine can actually worsen some thyroid conditions. Iodine supplements help only when deficiency is the proven cause, which your doctor determines.

Your thyroid result: what to do next

Find the row that matches your situation — every path ends with your doctor, because thyroid results are never read alone:

If your result is…	Sensible next step	Talk to your doctor when…
TSH mildly raised, free T4 normal, no symptoms	Usually rechecked in 6–12 weeks; note symptoms, family history and pregnancy plans	TSH keeps rising, antibodies are positive, or you are planning pregnancy
Any abnormal result in pregnancy or while planning it	Discuss promptly — targets are tighter and thyroid levels affect foetal development	As soon as you know; do not wait for the next routine visit
Abnormal during another illness (infection, surgery, hospital stay)	Ask about repeating after recovery — serious illness transiently alters thyroid levels	The repeat, taken when well, is still abnormal
On thyroid treatment and the result is out of range	Do not adjust the dose yourself; mention the time of day you tested and any supplements (especially biotin)	Symptoms change, or a new medicine or supplement was started
TSH normal but thyroid symptoms persist	Discuss free T4 and antibodies with your doctor — TSH is the best first screen, not an infallible one	Symptoms continue despite the normal TSH

Thyroid test price in India

A thyroid profile (TSH + free T4, sometimes free T3) typically costs ₹600–₹1,200, though prices vary by city and lab; a standalone TSH test costs less, while antibody tests such as anti-TPO are usually priced separately. Where possible, choose a NABL-accredited lab, and remember the range printed on your own report — especially the pregnancy-specific ranges — is the one that counts.

Frequently Asked Questions

Do I need to fast for a thyroid test?

Fasting is not usually required, but because TSH varies through the day (it is highest in the early morning), consistency in timing helps when monitoring: many clinics prefer a morning sample.

Can medicines affect thyroid results?

Yes. Biotin supplements can interfere with some thyroid assays, and drugs such as steroids, lithium and amiodarone affect thyroid function. Always mention your supplements and medicines.

Why is TSH checked before T4?

Because TSH is the most sensitive early indicator of thyroid dysfunction: it often changes before free T4 moves outside the normal range.

Are thyroid problems lifelong?

Autoimmune hypothyroidism usually requires lifelong hormone replacement, but some thyroid disturbances, such as those after pregnancy or a viral thyroiditis, can be temporary and resolve.

How much does the Thyroid test cost in India?

There is no single fixed price — it varies by city, lab, and whether the test is ordered alone or as part of a panel. NABL-accredited labs usually publish their rates online, so it is worth comparing a couple near you. Whatever you pay, the reference range printed on your own report is what counts — discuss the result with your doctor.

What is the difference between a TSH test and a full thyroid panel?

A TSH test measures the pituitary signal alone and is the usual first-line screen; a full panel adds free T4 and sometimes free T3. TSH alone is often enough for monitoring, while the panel is used when TSH is abnormal or the picture needs confirming. Our dedicated TSH page explains the single test in more detail.

What is anti-TPO and why is it ordered with thyroid tests?

Anti-TPO is an antibody test that helps find the cause of thyroid dysfunction: a positive result points towards Hashimoto's thyroiditis, the commonest cause of an underactive thyroid. It is ordered to explain abnormal results, not as a routine screen.

Can thyroid results be abnormal during another illness?

Yes. Serious infections, surgery or prolonged hospitalisation can transiently alter TSH and thyroid hormone levels without any real thyroid disease — a pattern doctors call non-thyroidal illness. An odd result in that setting is usually rechecked after recovery rather than treated.

Do I need the full panel every time I retest?

Usually not. Once a diagnosis is established, TSH alone is often enough for routine monitoring, with free T4 added when TSH is abnormal or the clinical picture changes. Follow your doctor's plan for which tests to repeat and how often.

Pharmacist's practical notes

TSH is usually the first and most sensitive test, and for routine monitoring it is often the only one needed. Free T4 and free T3 add context when TSH is abnormal or when the clinical picture is unclear. If your doctor ordered TSH alone, that is usually a deliberate, sufficient choice — not a test that was forgotten.

When the cause of thyroid dysfunction needs pinning down, antibodies enter the picture. Anti-TPO points towards Hashimoto's thyroiditis in an underactive gland, and TSH-receptor antibodies towards Graves' disease in an overactive one. These are cause-finding tests, ordered when the basic results need explaining, not as routine add-ons.

Thyroid results can be thrown off by non-thyroidal illness: a serious infection, surgery or prolonged hospitalisation can transiently alter TSH and thyroid hormones without any real thyroid disease. A mildly odd result during or just after another illness is usually rechecked after recovery rather than treated.

A full panel every time is not always necessary. Once a diagnosis is established and treatment is stable, many doctors follow TSH alone at intervals. What matters most is consistency — similar timing of the blood draw, and mentioning biotin supplements and medicines (steroids, lithium, amiodarone) that can skew the assay.

References

Sources cited on this page. PubMed links open the original abstract.

Cooper DS. Hyperthyroidism. Lancet. 2003;362(9382):459–468. PMID 12927435 · doi:10.1016/S0140-6736(03)14073-1
Stott DJ, Rodondi N, Kearney PM, et al. Thyroid Hormone Therapy for Older Adults with Subclinical Hypothyroidism. N Engl J Med. 2017;376(26):2534–2544. PMID 28402245 · doi:10.1056/NEJMoa1603825
Alexander EK, Pearce EN, Brent GA, et al. 2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum. Thyroid. 2017;27(3):315–389. PMID 28056690 · doi:10.1089/thy.2016.0457

Medical Disclaimer: TSH ranges can vary by laboratory and are different during pregnancy. This information is for educational purposes only. Never start or stop thyroid medication without consulting your endocrinologist or physician.