Testosterone (Total & Free)
Also known as: Total testosterone, Free testosterone, Serum T
Testosterone is the primary male sex hormone and plays important roles in muscle mass, bone density, libido, and mood in both men and women. Levels peak in the morning and decline with age.
Venous blood (serum separator tube — early morning draw essential)
24–48 hours
Not required
Hormones
Reference Ranges
| Measurement | Reference Range | Unit |
|---|---|---|
| Total testosterone (men) | 300 – 1000 | ng/dL |
| Total testosterone (women) | 15 – 70 | ng/dL |
| Free testosterone (men) | 50 – 210 | pg/mL |
Reference ranges are typical adult values. Your laboratory may use slightly different intervals — always use your lab's reported reference.
What This Test Measures
Total testosterone measures all circulating testosterone, most of which (97–99%) is bound to sex hormone-binding globulin (SHBG) or albumin. Only free testosterone — the unbound 1–3% — can enter cells and exert hormonal effects. Conditions that alter SHBG (obesity lowers it; age and liver disease raise it) change the free:total ratio without changing total testosterone.
When Is This Test Ordered?
- Delayed puberty or hypogonadism investigation in men
- Infertility evaluation
- Erectile dysfunction workup
- Polycystic ovary syndrome (PCOS) in women
- Monitoring testosterone replacement therapy
- Unexplained fatigue, low libido, or mood disturbance
When Results Are High
High testosterone in men rarely requires investigation unless it accompanies erythrocytosis, sleep apnoea, or is medication-induced. In women, elevated testosterone (above 70 ng/dL) suggests PCOS, congenital adrenal hyperplasia, or androgen-secreting tumour.
When Results Are Low
Low testosterone in men (below 300 ng/dL on two morning measurements) defines hypogonadism. Causes are primary (testicular failure — high LH) or secondary (pituitary/hypothalamic dysfunction — low LH). Symptoms include low libido, fatigue, loss of muscle mass, mood changes, and osteoporosis risk.
Factors That Can Affect Your Result
- Time of day — testosterone peaks at 7–10am, troughs in the afternoon by 35%
- Acute illness, stress, and sleep deprivation suppress testosterone
- Obesity lowers SHBG and total testosterone — but free testosterone may be adequate
- Alcohol chronically suppresses testosterone production
- Opioids significantly suppress the hypothalamic-pituitary-gonadal axis
Tracking This Test Over Time
Always recheck a borderline low testosterone with a second morning draw before starting treatment. The intra-individual variability of testosterone is 20–30%, making a single low value unreliable for diagnosis. Track both total and free testosterone — some men with low-normal total testosterone have adequate free levels.
Track your Testosterone in LoomsRelated Tests
Medical disclaimer
This page is for educational purposes only and does not constitute medical advice. Reference ranges vary between laboratories, and results must be interpreted in the context of your symptoms, history, and other tests. Always discuss your results with your healthcare provider. Content reviewed by the Looms medical team, 2026-06-01.