Testosterone Levels and Measurements in Adult Males

Understanding Testosterone Measurements

Total testosterone is generally considered normal in the range of 300-800 ng/dL (10.4-27.7 nmol/L) in most laboratories, according to the American Gastroenterological Association 1
Morning measurements are critical as testosterone levels naturally fluctuate throughout the day, with highest levels typically occurring in the morning, as suggested by the American College of Physicians 2
The diagnosis of low testosterone should only be made after two total testosterone measurements are taken on separate occasions, both conducted in early morning fashion, as recommended by the American College of Physicians 2

Testosterone deficiency in males is associated with energy imbalance, impaired glucose control, reduced insulin sensitivity, dyslipidemia, increased abdominal fat mass, and reduction in lean body mass, according to the American Gastroenterological Association 1
Low bioavailable testosterone can affect sexual function even when total testosterone appears normal, as reported by the American College of Physicians 3, 4
The American College of Physicians suggests that clinicians discuss testosterone treatment in men with age-related low testosterone with sexual dysfunction who want to improve sexual function 4
Treatment should be discontinued if there is no improvement in sexual function within 12 months, as recommended by the American College of Physicians 4

Bioavailable testosterone is particularly important to measure in men with obesity, as they may have low total testosterone due solely to low sex hormone-binding globulin but normal free testosterone levels, according to the American Gastroenterological Association 1
Many men receive testosterone therapy without proper diagnosis - up to 25% of men who receive testosterone therapy do not meet the criteria to be diagnosed as testosterone deficient, as noted by the American College of Physicians 2
Nearly half of men placed on testosterone therapy do not have their testosterone levels checked after therapy commences, as reported by the American College of Physicians 2