Testosterone testing measures the primary male sex hormone in blood. The testosterone test is ordered for evaluating low libido, erectile dysfunction, infertility, and other symptoms in men, as well as evaluating elevated testosterone in women (PCOS workup) or other conditions. Total testosterone and free testosterone provide complementary information. This guide covers what each measures, normal ranges, and clinical applications.
Total vs free testosterone
Most circulating testosterone is bound to sex hormone-binding globulin (SHBG) and albumin. Only a small fraction (1-3%) circulates as free testosterone, which is biologically active.
Total testosterone: Sum of all testosterone (bound and free).
Free testosterone: Only the unbound, biologically active fraction.
SHBG levels affect total testosterone independent of actual androgenic activity. High SHBG (aging, hyperthyroidism, liver disease) elevates total testosterone without raising free testosterone. Low SHBG (obesity, insulin resistance, hypothyroidism) lowers total testosterone without changing free testosterone significantly.
Reference ranges (men)
- Total testosterone: 280-1100 ng/dL adult range
- Free testosterone: 8.7-25.1 pg/mL (varies by lab)
- SHBG: 10-80 nmol/L
Total testosterone declines about 1-2% per year after age 30-40 in men.
Reference ranges (women)
- Total testosterone: 15-70 ng/dL premenopausal
- Total testosterone: under 35 ng/dL postmenopausal
When testosterone is tested
Men with possible hypogonadism:
- Low libido
- Erectile dysfunction
- Fatigue, depression, decreased muscle mass
- Infertility
Women with possible androgen excess:
- Hirsutism (excess hair growth)
- Irregular menses
- PCOS workup
- Infertility
The Endocrine Society recommends measuring morning total testosterone (between 7 and 10 AM) given diurnal variation, with confirmatory repeat testing for low values.
Low testosterone in men
Diagnosing male hypogonadism requires:
- Symptoms consistent with hypogonadism
- Total testosterone below 300 ng/dL on two morning measurements
- Confirmation of cause (primary vs secondary hypogonadism)
Causes include primary testicular failure, secondary (pituitary/hypothalamic) causes, obesity, sleep apnea, medications, and aging itself.
Testosterone replacement therapy considerations
Treatment of male hypogonadism involves testosterone replacement (gel, injection, patch) when symptoms warrant. Risks and considerations:
- Cardiovascular safety (FDA guidance has evolved)
- Erythrocytosis (hematocrit elevation)
- Prostate effects (PSA monitoring)
- Fertility suppression
- Sleep apnea worsening
Treatment requires monitoring including testosterone levels, hematocrit, and PSA.
Frequently Asked Questions
What time of day should testosterone be tested?
Morning (7-10 AM) since testosterone has diurnal variation with morning peaks.
Should I get total or free testosterone?
Total is standard initial test. Free testosterone is added when SHBG abnormalities are suspected or total is borderline.
Do I need to fast?
Not strictly required, though some labs prefer fasting.
What’s a normal testosterone for my age?
Reference ranges are typically not age-adjusted. The same 280-1100 ng/dL applies to most adult men, though some clinicians consider age-specific norms.
How often should testosterone be checked?
For diagnosis: at least two morning measurements. For monitoring on therapy: every 3-12 months depending on stability.
The bottom line on the testosterone test
Testosterone testing is essential for evaluating hypogonadism in men and androgen excess in women. Morning total testosterone is the standard initial test. Diagnosis requires repeated low values plus symptoms. Treatment with testosterone replacement is indicated for symptomatic hypogonadism with appropriate monitoring. Discuss results with your healthcare provider in clinical context.