Read a thyroid blood test result one value at a time: enter a TSH, Free T4 or Free T3 number to see if it sits below, within or above a typical adult range. Informational only, 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 to Read Thyroid Blood Test Results
Compare each value with its reference range, in the same units, and note whether it is below, within or above. Using this tool’s example ranges, a TSH of 2.5 mIU/L is within 0.4 to 4.0, while 5.2 mIU/L is above it. Doctors read TSH and Free T4 together, with your symptoms.
| Test | Example typical range used here |
|---|---|
| TSH | 0.4 to 4.0 mIU/L |
| Free T4 | 0.8 to 1.8 ng/dL, or 12 to 22 pmol/L |
| Free T3 | 2.3 to 4.2 pg/mL, or 3.1 to 6.8 pmol/L |
- Find the value and its unit on your report, for example TSH 5.2 mIU/L.
- Find the range beside it; the example range here is 0.4 to 4.0 mIU/L.
- Compare: 5.2 is greater than 4.0, so it is above the typical range.
- Take the result, with your other values and symptoms, to your doctor.
How the Checker Works
It places one lab value against a common adult reference range. It does not interpret your overall thyroid picture.
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) |
Is a TSH of 4 normal? Against the 0.4 to 4.0 example range it sits within, right at the top. Is a TSH of 5.5 high? It is above that range, though only your doctor can say whether it matters.
What Does High TSH Mean in a Blood Test?
A high TSH often means the pituitary is pushing the thyroid harder, but it is not a diagnosis on its own. Ranges differ between labs, so the one on your own report takes priority. The normal Free T4 range may be in pmol/L or ng/dL, so check the units.
- Biotin supplements, common in hair and nail products, can interfere with some thyroid assays, so tell whoever orders the test if you take them.
- Pregnancy changes thyroid ranges, so this tool is not suitable for results taken during pregnancy.
- If you take levothyroxine, ask whether to take it before or after the blood draw, and keep the timing consistent between tests.
Use the result to prepare questions for your appointment, not to start or change treatment. The thyroid function tests article on Wikipedia explains how each marker relates to the others.
Common questions about thyroid test results
How do I read thyroid blood test results?
Compare each value with the reference range printed on your report, using the same units. With this tool’s example ranges, a TSH of 2.5 mIU/L is within 0.4 to 4.0, while 5.2 is above it. Only a doctor can say what that means for you.What does high TSH mean in a blood test?
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.Is a TSH of 4 normal?
Against this tool’s example range of 0.4 to 4.0 mIU/L, a TSH of 4.0 sits within the range, right at the upper edge. Your lab’s own range may differ, so check the report and ask your doctor.Is a TSH of 5.5 high?
It is above this tool’s example range of 0.4 to 4.0 mIU/L. A single value just outside a range can still be normal for you, so a doctor decides whether it needs repeat testing or no action.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.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.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.