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.
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.
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.
How the Thyroid Function Checker Works
The Thyroid Function Checker takes one lab value at a time — TSH, Free T4, or Free T3 — and shows whether it falls below, within, or above a common adult reference range. It does not interpret your overall thyroid picture; it simply plots a single number against typical lab boundaries so you have context before you talk to your doctor.
Formula: For your chosen test and unit, the tool compares your Result (v) against a lower bound (lo) and upper bound (hi): if v < lo → "Below typical range"; if v > hi → “Above typical range”; otherwise → “Within typical range.” The example ranges used are TSH 0.4–4.0 mIU/L; Free T4 0.8–1.8 ng/dL or 12–22 pmol/L; Free T3 2.3–4.2 pg/mL or 3.1–6.8 pmol/L.
- Test — which thyroid lab value you’re checking: TSH, Free T4 (FT4), or Free T3 (FT3)
- Result — the numeric value from your lab report, entered exactly as printed
- Units — the unit your lab used (e.g. mIU/L for TSH; ng/dL or pmol/L for FT4; pg/mL or pmol/L for FT3), so the right reference range is applied
Example Scenarios
| Test | Result | Unit | Position vs typical range |
|---|---|---|---|
| TSH | 2.5 | mIU/L | Within typical range (0.4–4.0) |
| TSH | 5.2 | mIU/L | Above typical range |
| TSH | 0.2 | mIU/L | Below typical range |
| Free T4 | 1.2 | ng/dL | Within typical range (0.8–1.8) |
| Free T4 | 25 | pmol/L | Above typical range (12–22) |
| Free T3 | 2.0 | pg/mL | Below typical range (2.3–4.2) |
Thyroid Function Checker FAQ
Can this tool diagnose hypothyroidism or hyperthyroidism?
No. It only shows where one lab number sits against a typical adult range. Diagnosing a thyroid condition requires a doctor to review your full test panel, symptoms and history — this tool is a reference point, not a diagnostic test.What does it mean if my TSH is above the typical range?
A high TSH often suggests the pituitary is working harder to prompt the thyroid, which can point toward an underactive thyroid, but it isn’t conclusive on its own. Your doctor usually checks it alongside Free T4 and your symptoms.Why do reference ranges differ between labs?
Labs use different equipment, testing methods and reference populations, so their “normal” ranges can vary slightly. The range printed on your own lab report is more accurate for you than any generic example range, including this tool’s.Should I enter Free T4 in ng/dL or pmol/L?
Use whichever unit your lab report shows, and select the matching unit in the tool. Entering the right number with the wrong unit selected will place it against an incorrect range.What if my Free T3 is within range but my TSH isn’t?
That’s common and part of why thyroid tests are read together rather than in isolation. A single out-of-range value doesn’t confirm a problem — only a clinician weighing all your results can interpret the full picture.Is a slightly high or low result something to worry about?
Not necessarily. Values just outside a reference range can still be normal for you, especially with borderline TSH results. Only a doctor can say whether a result needs follow-up, repeat testing, or no action at all.Related Calculators
Thyroid results are just one piece of your overall health picture. If you’re reviewing labs, the blood sugar level checker and anemia risk calculator cover other common blood-test concerns, while the blood pressure tracker helps you log another key vital sign to bring to your next appointment.