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Total T3 in two units: the short answer
To convert total t3 from ng/dL to nmol/L, multiply by 0.01536. To go back from nmol/L to ng/dL, multiply by 65.1 (or divide by 0.01536). For example, 150 ng/dL × 0.01536 = 2.30 nmol/L. The converter above works in both directions and shows where the result sits against typical reference ranges.
What the test measures
Total T3 includes bound and free triiodothyronine. US labs report it in ng/dL; SI labs in nmol/L. With a molar mass of 651.0 g/mol, 1 ng/dL = 0.01536 nmol/L, and 1 nmol/L = 65.1 ng/dL.
Why the units differ
T3 is mainly measured when hyperthyroidism is suspected but free T4 is normal (T3 toxicosis). Comparing a US result with a European range requires converting.
Where the factor comes from
The conversion factor comes from the molar mass (650.97 g/mol) and the volume units on each side. Laboratories may round the factor slightly differently, which can change the last digit but never the clinical meaning.
How to convert step by step
- Check the unit printed next to the result on your report – ng/dL or nmol/L.
- ng/dL → nmol/L: multiply by 0.01536.
- nmol/L → ng/dL: multiply by 65.1.
- Round to the same number of decimals your lab uses.
Worked example in reverse: 1.23 nmol/L × 65.1 = 80.1 ng/dL.
Total T3 conversion chart
| ng/dL | nmol/L |
|---|---|
| 50 | 0.77 |
| 60 | 0.92 |
| 80 | 1.23 |
| 100 | 1.54 |
| 120 | 1.84 |
| 150 | 2.3 |
| 180 | 2.76 |
| 200 | 3.07 |
| 250 | 3.84 |
| 300 | 4.61 |
| nmol/L | ng/dL |
|---|---|
| 0.77 | 50.1 |
| 0.92 | 59.9 |
| 1.23 | 80.1 |
| 1.54 | 100.3 |
| 1.84 | 119.8 |
| 2.3 | 149.7 |
| 2.76 | 179.7 |
| 3.07 | 199.9 |
| 3.84 | 250 |
| 4.61 | 300.1 |
Total T3 levels: what the numbers mean
| Category | ng/dL | nmol/L |
|---|---|---|
| Typical adult rangeAbout 1.2–3.1 nmol/L; varies by lab and age | 80 – 200 | 1.23 – 3.07 |
Typical adult reference interval. T3 often falls during acute illness (low-T3 syndrome) without thyroid disease.
Typical adult reference interval. T3 often falls during acute illness (low-T3 syndrome) without thyroid disease.
Interpreting total t3 results
Most T3 is made outside the thyroid by converting T4 in the liver and other tissues. That is why T3 drops in starvation, after surgery and in serious illness, and why it is a poor test for hypothyroidism. Its main value is in suspected overactivity: a high T3 with suppressed TSH supports hyperthyroidism even when free T4 is still normal.
A single result outside the reference range is common and often not significant on its own. Reference ranges are set so that about 1 in 20 healthy people fall outside them, and every laboratory sets its own limits for its method. Use the range printed on your report and discuss results with the clinician who ordered the test.
When to see a doctor
Contact your clinician if a result is flagged as abnormal and you have symptoms, if a value is far outside the range, or if results are changing over time. This page explains units; it cannot diagnose or replace medical advice.
Frequently asked questions
What is 2 nmol/L T3 in ng/dL?
2 × 65.1 = 130 ng/dL.
Why is my T3 low when I'm sick?
Illness, fasting and some medicines reduce conversion of T4 to T3. This is usually not a thyroid problem and is not treated with thyroid hormone.
Can I use this converter for any lab?
Yes for the unit conversion, which is fixed by chemistry. Reference ranges differ between labs and methods, so compare your converted value with your own lab's range.