Thyroid Health

Thyroid Test (TSH, T3, T4): What the Numbers Mean & When to Test

March 15, 2026
Admin
2 min read
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Endocrinologist examining a young woman's thyroid gland in the neck

The thyroid is a small, butterfly-shaped gland at the front of the neck that produces hormones controlling how your body uses energy. These hormones influence your heart rate, breathing, digestion, weight and even your mood. A thyroid test measures the level of these hormones in your blood when a thyroid problem is suspected.

Understanding the Three Markers

A thyroid test usually measures three key markers:

  • T3 (triiodothyronine) — the active hormone that drives your metabolism.
  • T4 (thyroxine) — a reserve hormone that the body converts into active T3 as needed.
  • TSH (thyroid stimulating hormone) — the control signal from the brain that tells the thyroid how much T3 and T4 to make.

Normal Ranges

Standard reference values are typically:

  • TSH: 0.4 to 4.0 mIU/L
  • T4: 4.5 to 11.0 mcg/dL
  • T3: 70 to 200 ng/dL

Reference ranges can vary slightly between laboratories, and targets differ during pregnancy or with certain medications. Your doctor interprets the numbers together, not in isolation.

Warning Signs of Thyroid Problems

Symptoms that may point to a thyroid imbalance include persistent tiredness, unexplained weight gain or loss, mood changes, hair loss, an irregular heartbeat, digestive issues, muscle weakness, sleep problems and changes in the skin.

When Should You Get Tested?

Doctors generally recommend a thyroid test when symptoms suggest a hormonal imbalance, during pregnancy, in people with autoimmune conditions, to monitor the effect of thyroid medication, or to investigate otherwise unexplained symptoms.

What Happens During the Test?

A thyroid test is a simple blood test. A healthcare professional draws a small sample from a vein in your arm. Tell them about any medicines you take, and check whether fasting is needed — for most thyroid tests it is not, though a morning sample is preferred.

You can book a thyroid profile at our NABL-accredited biochemistry lab in Delhi & Noida, with same-day reporting and home sample collection. Contact us to schedule your test.