TSH (Thyroid-Stimulating Hormone) Test
Reviewed
A TSH test measures a pituitary hormone that helps regulate thyroid hormone production.
Preparation and collection
Follow the ordering clinician's instructions about timing, biotin-containing supplements, pregnancy, recent illness, and thyroid medicine schedules. Do not stop a medicine or supplement unless instructed.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- Intervals and targets differ in pregnancy, childhood, older age, pituitary disease, and during treatment.
- Biotin and some medicines can interfere with certain assays.
What to do next
Follow-up may include free T4, free T3, thyroid antibodies, repeat testing, or treatment review depending on the pattern.
Evidence source
U.S. National Library of Medicine: TSH (Thyroid-Stimulating Hormone) Test