FaridabadBy Dr B.C. Gupta, MD · 2026-08-15
A TSH test measures thyroid stimulating hormone, the chemical that tells your thyroid gland how much thyroid hormone to make. It is the most common first test for checking how well your thyroid is working.
What does the test measure?
TSH is made by the pituitary gland at the base of the brain. It signals the thyroid, a small gland in the front of the neck, to release thyroid hormone. When thyroid hormone levels are low, TSH rises to push the thyroid harder. When they are high, TSH falls. So a single TSH reading gives a useful picture of thyroid function.
How to prepare
No special preparation is needed for a TSH test. You do not need to fast. The sample is a simple blood draw, usually from a vein in the arm, and the result is typically available the same day. If you take thyroid medicine, ask your doctor whether to take it before or after the test, because timing can affect the result.
What a high or low result can mean
A high TSH often points to an underactive thyroid, a condition where the gland is not making enough hormone. A low TSH can point to an overactive thyroid, where too much hormone is being made. These are general patterns, not diagnoses. Many things affect TSH, including medicines, pregnancy, and recent illness, so the result must be read alongside your symptoms and other tests by a doctor.
When is it ordered?
Doctors commonly order a TSH test for symptoms such as tiredness, weight change, feeling too hot or too cold, or changes in heart rate. It is also part of routine health checks and is checked during pregnancy. If your result is outside the usual range, your doctor will explain what it means for you and what to do next.
This article is for general information only and is not medical advice. Always discuss your results and any health concerns with your doctor.
