Total testosterone
Also called Serum testosterone, TT
Total testosterone is a blood test that measures all of the testosterone in your bloodstream, both the portion bound to proteins and the small unbound, or free, portion. It is the most commonly ordered testosterone test and the usual starting point when low testosterone is suspected.
Most testosterone travels attached to proteins, chiefly SHBG (sex hormone-binding globulin) and albumin. Total testosterone counts all of it, which is why it is read alongside SHBG and, when needed, free testosterone: the total says how much is circulating, not how much is available to tissues. Guidelines from the American Urological Association and the Endocrine Society base the diagnosis on repeated early-morning total testosterone results together with symptoms, never on a single number.
Why it matters after 45
It is normal for testosterone to decline with age, and conditions that become common in midlife, such as type 2 diabetes, are among those the AUA lists as reasons to measure it. Because levels vary through the day and between draws, and because SHBG also shifts with weight, thyroid function and medicines, the timing and repetition of the test, and what is measured with it, matter more than any one result.
Where it comes up
- Low testosteronethe condition this test is ordered to investigate
- Getting the testosterone test rightmorning draws, repeat tests and what else is measured
- Testosterone levels by agehow reference ranges work and how a result is interpreted
- Comprehensive Lab Panelthe baseline panel that includes the hormone markers
Related terms
References
- MedlinePlus. Testosterone Levels Test. U.S. National Library of Medicine. https://medlineplus.gov/lab-tests/testosterone-levels-test/
- American Urological Association. Evaluation and Management of Testosterone Deficiency (AUA Guideline). https://www.auanet.org/guidelines-and-quality/guidelines/testosterone-deficiency-guideline
- Endocrine Society. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline, 2018. https://www.endocrine.org/clinical-practice-guidelines/testosterone-therapy
Definitions here are educational and are not medical advice. They explain what a term means; the pages linked above cover what it means for you, and a clinician reviews your own results. Editorial & medical review policy · All glossary terms