Biomarker education
TSH: What It Measures & Why People Track It
Also called: Thyroid-stimulating hormone
TSH is a pituitary hormone measured when clinicians evaluate thyroid-related lab context.
General biomarker education — not personalized medical advice. Learn more
Result on your report
IllustrativeTSH
2.1
Range: 0.4 – 4.0
What it generally measures
TSH helps regulate thyroid hormone production. Labs report a blood concentration; related thyroid hormones may appear on the same or separate reports.
Common units on reports: mIU/L
Why people track it over time
People with serial thyroid labs often compare TSH over time. Timing of medications and lab methods can affect interpretation — ask your clinician.
Changes over time do not by themselves establish a diagnosis. Learn more
Questions you might ask a healthcare professional
Questions to bring
IllustrativeRelated markers
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What this page does not do
TSH assays are not interchangeable. A range printed by one laboratory may not apply to another. Medication timing and illness can also influence results. This page does not diagnose thyroid disease.
Common questions
- What is TSH on a blood test?
- TSH is thyroid-stimulating hormone, typically reported in mIU/L with an assay-specific reference interval.
- Should TSH be read with free T4?
- They are complementary when both were ordered. Not every thyroid order includes both. Ask how your clinician wants to read the pair.
- Why did my TSH range change?
- Different assays use different intervals. Compare TSH to the range printed on that report, not to a range from another lab or a website.