Testosterone Blood Test

Testosterone is the primary androgen (male sex hormone), produced mainly in the testes in men and in smaller amounts by the ovaries and adrenal glands in women. This test measures total testosterone—the sum of testosterone bound to proteins (sex hormone-binding globulin and albumin) plus the small amount that is free (unbound). Total testosterone is the standard first-line test for assessing testosterone status. In men, testosterone is essential for the development of male characteristics during puberty and continues throughout life to regulate libido and sexual function, sperm production, muscle mass and strength, bone density, fat distribution (preventing central obesity), red blood cell production, mood and mental wellbeing, energy and motivation, and cognitive function. Testosterone levels naturally decline gradually after age 30, at approximately 1-2% per year, though this decline varies significantly between individuals. Low testosterone (hypogonadism) can occur at any age and may be due to testicular problems (primary hypogonadism), pituitary/hypothalamic problems (secondary hypogonadism), or age-related decline (late-onset hypogonadism). Normal testosterone in men is typically 8.6-29 nmol/L in the morning. Levels below 8 nmol/L are generally considered low; levels 8-12 nmol/L are borderline and clinical context matters; levels above 12 nmol/L are usually adequate. However, symptoms don't always correlate perfectly with levels, and some men have symptoms despite "normal" total testosterone (possibly due to low free testosterone or individual sensitivity). In women, normal testosterone is approximately 0.5-2.5 nmol/L. Elevated testosterone in women may indicate polycystic ovary syndrome (PCOS), androgen-secreting tumours (rare), or exogenous androgen use. Very high testosterone (>5 nmol/L) in women warrants prompt investigation. Results outside the normal range may need a follow-up with your GP.