TSH Test Results Explained: What Your Number Means

TSH results, explained

Enter your value to see whether it falls in the typical range and what that means. This is an educational explainer — not a diagnosis, and your entry never leaves your browser.

Enter your TSH value

mIU/L

Also written µIU/mL — the numbers are the same.

This is educational, not a diagnosis. Reference ranges vary between labs and assays — the range printed on your report is the one that applies to you, and a single value is interpreted with your history and symptoms by a clinician. Your entry stays in your browser; nothing is stored or sent anywhere.

Reference ranges: American Thyroid Association — Thyroid Function Tests. View source

What TSH measures

TSH is made by the pituitary gland to tell the thyroid how much thyroid hormone to release. It's the first-line screen for thyroid function.

Why the test is done

To check for an underactive thyroid (hypothyroidism) or overactive thyroid (hyperthyroidism), or to monitor thyroid treatment.

Typical reference ranges

Typical adult reference bands for TSH (mIU/L)
Band	What it may mean
Below typical range	A low TSH can point toward an overactive thyroid (hyperthyroidism), where the pituitary dials back its signal. It can also occur early in treatment. It needs interpretation alongside free T4/T3 by a clinician.
Within typical range	This is the commonly used adult reference range for TSH. Within it, thyroid function is usually considered normal — though 'normal' targets can differ in pregnancy and during treatment.
Mildly above range	A mildly high TSH can suggest subclinical or early hypothyroidism (an underactive thyroid). Clinicians often repeat the test and check thyroid antibodies before deciding anything.
Above typical range	A higher TSH suggests the thyroid may be underactive (hypothyroidism), so the pituitary is pushing harder. This is interpreted with free T4 and your symptoms by a clinician.

Ranges shown are typical adult values from American Thyroid Association; your own lab's printed range applies to you. View source.

Frequently asked questions

What is a normal TSH level?

A commonly used adult reference range is about 0.4 to 4.0 mIU/L, but the exact range on your lab report is the one that applies to you, and targets differ in pregnancy and during thyroid treatment.

Does a high TSH mean I have hypothyroidism?

Not by itself. A high TSH can suggest an underactive thyroid, but clinicians confirm it with a free T4 test, sometimes thyroid antibodies, a repeat test, and your symptoms before making a diagnosis.