Make sense of a thyroid lab result. This free checker shows whether a TSH, Free T4 or Free T3 value sits below, within or above a typical adult reference range — informational only, and never a substitute for your doctor’s interpretation.
⚠ Informational only — not a diagnosis. This shows where a lab value sits against typical adult reference ranges, which vary by lab, age, pregnancy and other factors. Thyroid results must be interpreted by a doctor, who often looks at several tests together. Don’t change any treatment based on this.
Your lab result
mIU/L
Enter the value exactly as shown on your lab report, and use your own lab’s reference range where given — it’s the most accurate for you.
Position vs typical range
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Choose a test and enter your result
Your result
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Test
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Typical adult range
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Interpretation
Ask your doctor
Reference ranges here are common examples only and differ between laboratories. A result outside a range isn’t automatically a problem, and a normal result doesn’t rule one out — only a clinician can interpret thyroid tests.
Use this free thyroid function checker to see where a lab result — TSH, Free T4 or Free T3 — sits against typical adult reference ranges. Enter the number from your report for an at-a-glance, informational comparison.
Important: this tool is informational only and is not a diagnosis. It simply shows whether a value you enter is below, within or above a typical reference range. It does not assess symptoms and cannot tell you whether you have a thyroid condition. Thyroid results must be interpreted by a doctor, who usually reviews several tests together.
What this thyroid checker shows you
A thyroid function checker compares a single lab value against a common adult reference range and reports its position — below, within, or above. It covers TSH, Free T4 and Free T3. It’s a quick way to make sense of a number on a report, but interpretation always belongs with your clinician.
What the thyroid tests measure
Test
What it is
Typical adult range*
TSH
Hormone from the pituitary that signals the thyroid
~0.4–4.0 mIU/L
Free T4
Available thyroxine in the blood
~0.8–1.8 ng/dL
Free T3
Available triiodothyronine
~2.3–4.2 pg/mL
*Examples only — every laboratory sets its own ranges, and they shift with age, pregnancy and the testing method. Always use your own report’s range where given.
Why thyroid results need a professional
Thyroid results can be counterintuitive — for example, TSH often moves in the opposite direction to thyroid hormone. A value just outside a range may be normal for you, and a value inside it doesn’t rule out an issue. Doctors interpret the tests together, alongside your history and sometimes repeat or additional testing.
How to use the thyroid checker
Select the test (TSH, Free T4 or Free T3).
Enter the result exactly as shown, choosing the matching units.
Read the position. Below, within or above the typical range.
Take it to your doctor for what it actually means.
Thyroid terms glossary
Term
What it means
TSH
Thyroid-stimulating hormone.
Free T4 / T3
The unbound, active thyroid hormones.
Reference range
The lab’s typical range for healthy adults.
Thyroid Function FAQ
What is a normal TSH level?
A common adult reference range for TSH is roughly 0.4–4.0 mIU/L, but
laboratories set their own ranges and they shift with age and pregnancy.
Always use the range printed on your own report, and have a doctor interpret
it.
What do TSH, Free T4 and Free T3 measure?
TSH is the signal from the pituitary that tells the thyroid to work; Free T4
and Free T3 are the available thyroid hormones in your blood. Doctors
usually look at them together rather than in isolation.
My result is outside the range — is something wrong?
Not necessarily. A value slightly outside a reference range can still be
normal for you, and ranges vary by lab. Only a clinician can say what a
result means, often with repeat or additional testing.
Why does TSH move opposite to thyroid hormone?
When thyroid hormone is low, the pituitary releases more TSH to push the
thyroid, so TSH rises; when hormone is high, TSH falls. This is one reason
thyroid results are easy to misread and need professional interpretation.
Can this checker diagnose a thyroid condition?
No. It only shows where a number sits against an example range and does not
consider symptoms or other tests. Diagnosis requires a healthcare
professional.
Is the thyroid function checker free to use?
Yes, this thyroid function checker is completely free, needs no sign-up, and
gives instant results in your browser. It is informational only and not a
substitute for medical advice.
