3 values
Thyroid Profile: Reading TSH, T3 and T4 Together
A thyroid report confuses people for a structural reason: one of its three numbers runs backwards. TSH is not a thyroid hormone at all — it is the pituitary's instruction to the thyroid, so it rises when the gland is underperforming.
When it is ordered
Ordered for tiredness, weight change, hair fall, irregular periods, in pregnancy, and to monitor anyone already on thyroid medication. Fasting is not usually required; a morning sample is preferred.
Every line on the report
| Test | Typical range | Unit | What it is |
|---|---|---|---|
| TSH | 0.4–4 | µIU/mL | The pituitary's instruction to the thyroid, not a thyroid hormone. It moves opposite to T3 and T4. |
| T3 (Total) | 80–200 | ng/dL | The active hormone, mostly converted from T4 elsewhere in the body. |
| T4 (Total) | 5–12 | µg/dL | The thyroid's main output. Read together with TSH — the pair is what carries the meaning. |
Ranges differ between laboratories. These are the values commonly printed on adult reports in India — always compare against the range printed on your own report, next to your own result.
How the values are read together
- High TSH with low T4 — an underactive thyroid. Tiredness, weight gain, feeling cold and dry skin are typical.
- Low TSH with high T3 or T4 — an overactive thyroid. Weight loss, palpitations and heat intolerance are typical.
- Abnormal TSH with normal T3 and T4 — the gland is keeping up under more instruction than usual. Whether that needs treating depends on the degree, your symptoms and whether you are pregnant.
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Frequently asked questions
What is the normal TSH range?
About 0.4–4.0 mIU/L for most adults, with different targets in pregnancy and some variation between labs and methods.
Why is TSH high when T3 and T4 are normal?
The pituitary is working harder to keep hormone levels in range — often called subclinical hypothyroidism. Whether it needs treatment is a decision for a doctor, not a number.
Should I fast for a thyroid test?
Usually not, though labs often prefer a morning sample because TSH varies through the day. If you take thyroid medicine, ask whether to take it before or after the draw and then stay consistent.