Testosterone (total)

Women: 0.3 to 1.7 nmol/L · Men: 8.6 to 29 nmol/L

Men run roughly 8.6 to 29 nmol/L on a morning sample and women 0.3 to 1.7, the lower limit in men differs between labs (some print 6.7, 8 or 10), and values fall with age.

Testosterone is the main male sex hormone, made by the testes in men and in much smaller amounts by the ovaries and adrenal glands in women. It supports muscle, bone, red blood cell production, body hair, sex drive and sperm production. The total test measures all of it in the blood, both the part bound to proteins and the small free part.

In men it is requested for low sex drive, erectile problems, tiredness, low mood, reduced body hair, infertility and before or during testosterone replacement. In women it is used for excess hair growth, acne, irregular periods and polycystic ovary syndrome.

• Testosterone replacement and anabolic steroid use
• Polycystic ovary syndrome, in women
• Morning sampling, as levels peak between 7am and 10am
• Rarely, ovarian, testicular or adrenal tumours
• Some inherited adrenal conditions
• Higher SHBG, which raises the total without changing the free part

• Older age, gradually, in the general population
• Heavier body weight and type 2 diabetes
• Afternoon or evening sampling
• Acute illness, poor sleep and heavy alcohol use
• Some medicines, including opioids, steroids and some hormone treatments
• Testicular, pituitary or hypothalamus problems
• Lower SHBG, which lowers the total without changing the free part

• Afternoon samples read lower; UK guidance is a morning sample before 11am, ideally fasting
• A single low value is commonly normal on repeat, so doctors ask for two morning samples
• Recent illness, poor sleep and alcohol lower it temporarily
• Female assays are less accurate at the low end, so small differences between labs are expected

Morning sample before 11am, ideally fasting, and not during an acute illness. Doctors usually repeat a low value on a second morning before drawing any conclusion. In men the result is read with SHBG and often LH.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.