What the testosterone (total) test shows
Total testosterone measures every testosterone molecule in the blood. Most travels bound — tightly to SHBG (sex hormone-binding globulin) and loosely to albumin — leaving only about 1–2% free. That total is the first-line check of testosterone status in both sexes, as MedlinePlus explains.
It differs from the fractions ordered with it. Free testosterone is only the unbound, active portion, which matters when SHBG shifts — obesity and type 2 diabetes lower it, ageing, an overactive thyroid and liver disease raise it — pulling the total up or down while the active hormone barely moves. About 95% of a man’s testosterone is made in the testes under pituitary control, per StatPearls; the rest is adrenal, the main source in women. It also peaks in the early morning, so the sample is drawn then.
Testosterone normal range
Testosterone is reported in ng/dL in the US and nmol/L elsewhere, and the two are not interchangeable: multiply ng/dL by 0.0347 for nmol/L (300 ng/dL ≈ 10.4 nmol/L). Values differ hugely by sex and, in men, fall with age:
| Group | ng/dL (conventional) | nmol/L (SI) |
|---|---|---|
| Men, adult (~19–49) | ~300–1000 | ~10–35 |
| Men, 50 and older | trend lower, often ~200–800 | ~7–28 |
| Women, adult | ~8–60 | ~0.3–2.1 |
| Children / through puberty | age- and stage-specific — use the lab’s range | — |
The Endocrine Society endorses a harmonized range of 264–916 ng/dL (9.2–31.8 nmol/L) in healthy young men and — with the American Urological Association — treats a morning total below 300 ng/dL (10.4 nmol/L), confirmed on a repeat and matched to symptoms, as the practical deficiency cutoff at any age. Women’s values are a fraction of this, measured best by mass spectrometry. Ranges depend on the lab, sex, age and time of day — read yours against your own report.
Why testosterone is low
In men, low total testosterone with symptoms is hypogonadism. LH and FSH split the cause in two, as StatPearls sets out:
- Secondary (low or normal LH/FSH): the brain’s signal is weak — the commonest, reversible group. Obesity and type 2 diabetes lead (fat converts testosterone to estradiol and dampens the pituitary), then opioids, glucocorticoids, anabolic steroids or testosterone use (which switch off natural production), high prolactin, sleep apnea, illness, and hemochromatosis (pituitary iron).
- Primary (high LH/FSH): the testes are failing — Klinefelter syndrome (commonest genetic cause), mumps orchitis, trauma, and chemotherapy or radiation.
Symptoms include low libido, erectile problems, fatigue, low mood and falling muscle — the Cleveland Clinic picture, and part of a men’s health check after 30. Levels also fall ~1–2% a year from the forties.
When is it urgent? Very low testosterone with headaches or loss of side vision suggests a pituitary tumor needing prompt imaging; delayed puberty in a boy should be assessed promptly.
Why testosterone is high
A raised testosterone matters most in women and children; in men it usually reflects supplementation. By frequency:
- Polycystic ovary syndrome (PCOS) — the commonest cause in women (irregular periods, acne, excess hair); it travels with insulin resistance, so HbA1c or glucose is checked too.
- Non-classic congenital adrenal hyperplasia, screened with 17-OH-progesterone, with a high adrenal source flagged by DHEAS.
- Exogenous androgens — testosterone or anabolic steroids; the usual reason for a high level in men.
- Androgen-secreting tumors of the ovary or adrenal gland — uncommon but important.
When is it urgent? Rapid virilization in a woman — a deepening voice, balding or fast-spreading body hair — points to an androgen-producing tumor and needs prompt assessment. In a child, early (precocious) puberty should be evaluated.
What to test alongside
Rarely interpreted alone, testosterone pairs with:
- Free testosterone — the active fraction, key when SHBG is abnormal.
- SHBG — the carrier; needed to interpret a borderline total and calculate free testosterone.
- LH and FSH — separate testicular (high) from pituitary (low/normal) causes.
- Prolactin — a high level suppresses testosterone; may signal a pituitary tumor.
- Estradiol — testosterone converts into it; relevant in gynecomastia and on therapy.
- DHEAS, 17-OH-progesterone and AMH — the female PCOS work-up.
- Metabolic and overlap checks: HbA1c or glucose (metabolic syndrome), ferritin (iron overload), hemoglobin (raised by therapy) and TSH (thyroid overlap).
What to do about an abnormal result
- Don’t self-treat. Never start testosterone, “T-boosters” or anabolic steroids on your own — they shut down natural production, can impair fertility, and won’t fix a level with another cause.
- Repeat it properly. One value is not a diagnosis: draw a fasting morning sample (7–10 am) and confirm a low result on a repeat.
- Find the cause. It is read with LH, FSH, SHBG and prolactin (plus DHEAS and 17-OH-progesterone in women) to separate testicular, pituitary and adrenal causes.
- Low testosterone in men: reversible drivers — weight gain, opioids, poor sleep, sleep apnea — come first; therapy is only for confirmed, symptomatic deficiency and needs monitoring of hematocrit and prostate health.
- High testosterone in women: the work-up separates PCOS from an adrenal or ovarian source; rapid virilization is urgent until a tumor is excluded.
- Who to see. Start with your GP or primary-care doctor, who refers men to an endocrinologist or urologist and women to a gynecologist.
Mini-FAQ
What is the difference between total and free testosterone?
Total counts all of it — the ~98% bound to SHBG and albumin plus the 1–2% free. Free testosterone is only the unbound, active part. Total is the first-line test; free is added when SHBG is off (obesity, ageing, thyroid or liver disease).
What is a normal testosterone level for a man?
Most labs use roughly 300–1000 ng/dL (about 10–35 nmol/L); the harmonized reference in healthy young men is 264–916 ng/dL. A morning level under ~300 ng/dL twice, with symptoms, points to deficiency. Levels fall slowly with age.
Why does testosterone have to be measured in the morning?
Testosterone peaks in the early morning and falls through the day, so a fasting sample around 7–10 am reads truest. A low value is confirmed on a second morning test.
What does high testosterone mean in a woman?
Most often polycystic ovary syndrome (PCOS), with irregular periods, acne and excess hair. Rapid virilization — a deepening voice, balding or fast-growing body hair — is a red flag for an androgen-producing tumor and needs prompt assessment.
Does low testosterone always need treatment?
No. Many have reversible causes — weight gain, opioids, poor sleep or illness — corrected first. Testosterone therapy is reserved for confirmed, symptomatic deficiency and needs ongoing monitoring.
