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TSH: what the thyroid test means in plain English

TSH stands for thyroid stimulating hormone. It is made by a gland in your brain and tells your thyroid how much thyroid hormone to produce.

Usually reported in mIU/L.

For education only. Lucidio does not diagnose, treat, or replace a doctor. Lab results should always be interpreted by a healthcare professional using the patient's symptoms, history, exam, and full lab report.

What this test measures

TSH is a signal, not the thyroid hormone itself. It shows how hard your body is asking the thyroid to work.

Because it is a signal, TSH can move in the opposite direction from what people expect, which is one reason it is easy to misread on your own.

Clinicians often order other thyroid tests alongside it before drawing any conclusion.

What low, normal, and high generally refer to

These are general descriptions of the words on a lab report — not an interpretation of your result.

Below the range

A result under the range means less signal than expected. On its own it does not identify a cause — that takes a clinician and usually more than one test.

Within the range

A result inside the range is what the lab considers typical for the population it uses for comparison.

Above the range

A result over the range means more signal than expected. Again, the reasons vary and need a clinician's read of your full results and symptoms.

Why a doctor might order it

  • During a general check-up or when screening is recommended.
  • When someone reports symptoms such as fatigue, weight changes, or feeling unusually hot or cold.
  • To monitor a thyroid condition already being managed.
  • As a follow-up to an earlier result outside the range.

Questions worth asking

  1. 1What is my TSH, and what range did this lab use?
  2. 2Do you want to check other thyroid tests alongside this one?
  3. 3Could anything I am taking affect this result?
  4. 4When should this be rechecked?

Want questions built around your own situation? Try Ask Me.

Have your own TSH (Thyroid Stimulating Hormone) result?

Enter your number and the range from your report, and Lucidio will explain it in plain English and suggest questions for your clinician.

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Source: MedlinePlus: TSH Test