Short answer: the testosterone test measures the main male sex hormone in the blood. Most reports give total testosterone, sometimes with free testosterone and SHBG, the protein that carries most of it. Levels are highest in the morning and vary from day to day, so doctors usually ask for a morning sample and a repeat before drawing conclusions. In the US the unit is ng/dL; in much of Europe it is nmol/L: nmol/L = ng/dL × 0.0347.
At a glance
| Measures | Testosterone in serum or plasma: total, and sometimes free and SHBG |
|---|---|
| Units | ng/dL (US) or nmol/L (Europe); 1 ng/dL = 0.0347 nmol/L |
| LOINC | 2986-8 (total), 2991-8 (free), 13967-5 (SHBG) |
| When taken | Usually in the morning, often repeated on another day |
| Ordered for | Symptoms of low testosterone, puberty, fertility, excess hair or irregular periods in women |
| Keep | Value, unit, range, date and time of the sample |
What the test measures
Testosterone is made mainly by the testes in men and in smaller amounts by the ovaries and adrenal glands in women. In the blood, most of it is bound to SHBG (sex hormone-binding globulin) and albumin; a small part is free. Total testosterone counts all of it. Because SHBG changes with age, weight, thyroid function and some medicines, a total result can look low or high while the free part is not, which is why some reports include SHBG or a calculated free testosterone.
Why the time of day matters
Testosterone follows a daily rhythm, highest in the early morning, especially in younger men. It also drops after illness, poor sleep, intense exercise or fasting. Clinical guidelines therefore ask for a morning sample and a confirmatory second test before any conclusion. If your report does not say when the sample was taken, write the time next to it.
How the result is written on the report
| Result on the report | LOINC code | Usual unit | Also seen as |
|---|---|---|---|
| Testosterone, total, serum or plasma | 2986-8 | ng/dL | nmol/L (×0.0347) |
| Testosterone, free | 2991-8 | pg/mL | pmol/L (×3.47) |
| SHBG | 13967-5 | nmol/L | — |
nmol/L = ng/dL × 0.0347: 450 ng/dL ≈ 15.6 nmol/L. Reference ranges depend on sex, age and the laboratory's method; use the range printed on your report.
Keeping the results in your record
Hormone results make sense in series: the same test, at the same time of day, over months. Add each report in Anpheros Daily, where values are kept with their unit, range and LOINC code and line up on one chart, or use the free lab results tracker to chart them without an account.
What this page does not do
It explains what the test is and how it is written. It does not interpret your result, diagnose low testosterone or recommend treatment: that needs symptoms, an examination and usually repeated tests, and is your doctor's job.
Sources
Frequently asked questions
Why do I need a second testosterone test?
Testosterone varies from day to day and through the day. Guidelines ask for a repeat morning sample so that a single low or high value is not taken as the whole picture.
How do I convert testosterone from ng/dL to nmol/L?
Multiply by 0.0347. For example, 300 ng/dL is about 10.4 nmol/L.
What is the difference between total and free testosterone?
Total counts all testosterone in the blood; free is the small part not bound to proteins. SHBG levels shift the balance, so doctors sometimes look at both.
Do women have their testosterone tested?
Yes, for example when periods are irregular or there is excess hair growth. Women's ranges are much lower than men's, and the report gives the range for the sex recorded.
Try it in Anpheros Daily
Photograph your lab report and Anpheros Daily lines up each value with its reference range, so you can compare reports from different laboratories.
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