A thyroid test (thyroid profile) is a blood test that measures TSH, T3 and T4 to check how well your thyroid gland is working. It detects hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid). TSH is usually the first and most sensitive marker, with a typical adult range of about 0.4–4.0 mIU/L.
What does the thyroid test measure?
Your thyroid is a small gland in the neck that sets the pace of your metabolism: energy, weight, heart rate, body temperature, mood and menstrual cycles. The brain’s pituitary gland controls it by releasing TSH.
- TSH (thyroid stimulating hormone): The pituitary’s signal to the thyroid. When the thyroid is underactive, TSH rises as the brain “pushes harder”. When it is overactive, TSH falls. This inverse relationship confuses many people reading their reports.
- T4 (thyroxine): The main hormone the thyroid makes. Reports may show total T4 or free T4 (the active, unbound portion).
- T3 (triiodothyronine): The more active hormone, mostly converted from T4 in body tissues.
Thyroid problems are common in India, particularly hypothyroidism in women, and often go unnoticed because early symptoms like tiredness, weight gain and hair fall are easy to blame on a busy life.
Thyroid test normal range (adults)
(some labs use 0.27–4.2)
Where does your result fall?
Enter your TSH value from your report. Not for use in pregnancy, which has its own ranges.
A general guide, not a diagnosis. The reference range on your own report takes priority, and a doctor should interpret any result outside it.
Pregnancy uses different, trimester-specific TSH ranges set by your doctor. Thyroid ranges differ noticeably between lab methods. Ranges vary between labs and methods. Always compare your result with the reference range printed on your own report.
What abnormal results can mean
- High TSH with low T4: Suggests hypothyroidism (underactive thyroid).
- High TSH with normal T4: Called subclinical hypothyroidism; often monitored rather than treated straight away.
- Low TSH with high T3/T4: Suggests hyperthyroidism (overactive thyroid).
- Results off while on thyroid medicine: Your dose may need review by your doctor.
Illness, some medicines and biotin supplements can affect results. Discuss your report with a doctor.
Who should get this test?
- People with symptoms: unexplained weight change, tiredness, feeling unusually cold or hot, hair fall, irregular periods, palpitations, or low mood.
- Women planning pregnancy or who are pregnant, and women over 35 as part of routine checks.
- People with diabetes, high cholesterol or a family history of thyroid disease.
- Anyone on thyroid medication, usually every 6–12 months once stable.
- Preparation: Fasting is not required. Take the sample at a consistent time, ideally morning, and before your thyroid tablet that day unless told otherwise. Stop biotin supplements 2 days before if your doctor agrees.
This page is for general information and is not a substitute for medical advice. Always interpret your results with a qualified doctor.