TSH, T3, T4 Explained: Reading Your Thyroid Report Without Panicking

A thyroid report has three main numbers and a lot of anxiety attached to them. Here is how to read it sensibly.

What Each Value Means

• TSH — the pituitary's signal to the thyroid. High TSH usually means an underactive thyroid; low TSH usually means overactive.
• T4 (free T4) — the main hormone produced by the thyroid gland
• T3 (free T3) — the active form used by tissues

Typical Adult Reference Ranges

• TSH: roughly 0.4–4.0 mIU/L
• Free T4: roughly 0.8–1.8 ng/dL
• Free T3: roughly 2.3–4.2 pg/mL

Ranges differ slightly between laboratories and methods — always read against the range printed on your own report, and different targets apply in pregnancy.

Common Report Patterns

• High TSH, normal T4 — subclinical hypothyroidism; often just monitored
• High TSH, low T4 — overt hypothyroidism; usually treated
• Low TSH, high T3/T4 — hyperthyroidism; needs prompt review
• All normal, symptoms persist — look at anaemia, vitamin D and B12 instead

Symptoms That Justify Testing

Weight change without diet change, hair fall, irregular periods, constipation, cold or heat intolerance, palpitations, low mood, or infertility investigations. Women over 35 and anyone with a family history should test annually.

Getting an Accurate Result

• Test in the morning; TSH varies through the day
• Take thyroid medication after the blood draw
• Mention biotin supplements — they can distort results
• Avoid testing during an acute illness

Add anti-TPO antibodies if hypothyroidism is confirmed, to check for Hashimoto's thyroiditis.

Book a thyroid profile in Gurugram with home sample collection. Testing follows NABL protocols; certification application submitted.