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). In India, thyroid disorders — especially hypothyroidism — are extremely common, particularly in women.
Thyroid Normal Range Chart
| 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 India, 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. TSH above 2.5 in the first trimester is considered elevated and needs treatment. Untreated hypothyroidism in pregnancy increases risk of miscarriage, premature birth and developmental problems in the baby. All pregnant women should have TSH checked early in pregnancy.
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.