Total testosterone is the sum of all testosterone in your blood, bound and unbound. It is the most-ordered androgen test and the headline number on most "low T" workups. It is also the test most likely to be misinterpreted, because testosterone changes hour by hour, year by year, and with anything from a poor night's sleep to a recent flu.
The Endocrine Society and the American Urological Association both say the same thing: a diagnosis of testosterone deficiency needs two morning draws below the reference range plus matching symptoms. A single 3 p.m. result is not a diagnosis. It is also not a reason to start a man on lifelong replacement.
What total testosterone measures
Testosterone is the primary androgen. In men it is made by the testes (Leydig cells); in women, smaller amounts come from the ovaries and adrenal glands. In circulation, testosterone exists in three forms:
- Bound to SHBG (sex hormone-binding globulin), about 40–60%, biologically inactive.
- Bound to albumin: about 40–50%, weakly bound and considered bioavailable.
- Free testosterone: about 1–3%, fully active.
"Total testosterone" sums all three. It is a useful first test in someone with normal SHBG, but can mislead when SHBG is unusually high (aging, hyperthyroidism, oral estrogen, total looks low but bioavailable is fine) or unusually low (obesity, insulin resistance, hypothyroidism, total looks normal but free is low).
Testosterone has a strong diurnal rhythm, peak around 8 a.m., trough late afternoon. Levels can vary 30–50% across a day. Testing should be done before 10 a.m. for diagnostic clarity. Acute illness, severe sleep loss, and aggressive caloric restriction also depress testosterone for days to weeks.
Testosterone reference ranges
| Demographic | Low | High | Unit |
|---|---|---|---|
| Adult men 19–39 | 264 | 916 | ng/dL |
| Adult men 40–59 | 220 | 750 | ng/dL |
| Adult men 60+ | 200 | 700 | ng/dL |
| Adult women | 8 | 60 | ng/dL |
| Postmenopausal women | 5 | 40 | ng/dL |
| Children, pre-puberty | 0 | 7 | ng/dL |
| AUA hypogonadism cutoff (men) | 0 | 300 | ng/dL |
The American Urological Association sets the male diagnostic threshold for hypogonadism at total testosterone below 300 ng/dL on two morning draws, with symptoms. The widely cited Endocrine Society reference range is 264–916 ng/dL (Travison et al., harmonized assay).
- Adult men 19–39: roughly 264–916 ng/dL. Median around 400–500 ng/dL.
- Adult men 40+: total testosterone declines about 1–2% per year. A 70-year-old's median sits closer to 300–400 ng/dL.
- Women: 8–60 ng/dL. Cycle and age-dependent; declines steadily after the mid-30s.
- Children pre-puberty: below 7 ng/dL.
"Optimal" is debated. Most endocrinologists would not treat asymptomatic men with values in the 300–500 range. The number that matters clinically is whether symptoms (low libido, erectile dysfunction, depressed mood, loss of muscle mass, fatigue, reduced morning erections) line up with reproducibly low values.
What high testosterone means
In men, high total testosterone is uncommon outside of exogenous use. The differential:
- Anabolic steroid or exogenous testosterone use: by far the most common cause. Often accompanied by suppressed LH and FSH and shrinking testicular volume.
- Androgen-secreting tumor: rare; testicular Leydig-cell tumor or adrenal tumor. Usually striking elevations and rapid clinical change.
- Congenital adrenal hyperplasia (late-onset), DHEA-S and 17-OH progesterone usually point the way.
- Lab error, recent injection of testosterone replacement: timing relative to dosing matters.
In women, elevated testosterone (>60 ng/dL, certainly >100) most often signals:
- Polycystic ovary syndrome (PCOS): typically modest elevation with hirsutism, irregular cycles, insulin resistance. Check DHEA-S, LH/FSH ratio, fasting insulin.
- Adrenal or ovarian tumor: sudden virilization (deepening voice, clitoromegaly, rapid hair growth) or testosterone above 200 ng/dL warrants urgent imaging.
- Congenital adrenal hyperplasia: non-classical forms surface in adolescence/adulthood.
What low testosterone means
Low testosterone in men is overwhelmingly secondary to lifestyle and metabolic factors, not primary testicular failure. The leading causes:
- Obesity and metabolic syndrome: the dominant driver in men under 60. Aromatization of testosterone to estradiol in adipose tissue plus suppressed gonadotropins. Weight loss restores testosterone in many men.
- Aging: gradual ~1% per year decline. Routine testosterone replacement for normal aging is not supported by evidence.
- Chronic opioid use: even moderate doses suppress the HPG axis substantially.
- Glucocorticoids: chronic prednisone or equivalent.
- Sleep apnea, severe insomnia, poor sleep: testosterone synthesis is sleep-dependent.
- Pituitary disease: prolactinoma, panhypopituitarism, hemochromatosis. Check prolactin, LH, FSH.
- Klinefelter syndrome (47,XXY): primary testicular failure with high LH/FSH and low testosterone. Often diagnosed during infertility workup.
- Recent severe illness, surgery, or starvation: transient suppression.
Symptoms attributable to low testosterone (low libido, erectile dysfunction, fatigue, depressed mood, loss of muscle mass) are non-specific. Many men with low values are asymptomatic, and many with classic symptoms have normal testosterone. Treat the patient, not the number.
Why one testosterone is almost never enough
Testosterone fluctuates more than almost any other hormone routinely measured. Sources of variability:
- Time of day: peak around 8 a.m., trough around 4 p.m. Always test before 10 a.m., fasting if possible.
- Recent illness, fever, or hospitalization: depresses testosterone for days to weeks.
- Acute sleep deprivation: one bad night drops levels measurably.
- Aggressive caloric restriction or overtraining: both suppress the HPG axis.
- SHBG abnormalities: total testosterone misleads when SHBG is high (aging, hyperthyroidism) or low (obesity, hypothyroidism). When values are borderline, check free testosterone too.
- Assay differences: older direct immunoassays are unreliable at low levels; LC-MS/MS is the gold standard for women and pediatrics.
For a borderline result, repeat once or twice in the morning before drawing conclusions. Symptoms that fluctuate should not be paired with a single low number.
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When to act on testosterone
- Two morning total testosterones below 264 ng/dL with consistent symptoms: meets diagnostic criteria for hypogonadism. Discuss treatment options.
- Total testosterone above 1000 ng/dL with normal SHBG, no exogenous use: investigate for tumor.
- Sudden virilization in a woman: testosterone above 150–200 ng/dL warrants urgent adrenal/ovarian imaging.
- Low testosterone with low LH/FSH: central (pituitary) workup including prolactin, MRI if indicated.
- Low testosterone with high LH/FSH: primary testicular failure; consider Klinefelter, prior infection, prior chemo/radiation.
- Infertility workup: testosterone alone is not enough; pair with semen analysis, FSH, LH, and prolactin.
This information is for educational purposes only and is not a substitute for professional medical advice. Always consult your healthcare provider about your lab results.
Tests that complete the picture
- Free testosterone: bioavailable fraction. Essential when SHBG is abnormal.
- SHBG: needed to interpret total testosterone correctly.
- LH and FSH: distinguish primary (testicular) from secondary (pituitary/hypothalamic) hypogonadism.
- Prolactin: rule out prolactinoma in any man with low testosterone and low gonadotropins.
- Estradiol: useful in men with gynecomastia, on testosterone replacement, or with obesity (high aromatization).
- DHEA-S: adrenal androgen contribution, especially in women with hyperandrogenism.
- HbA1c and fasting insulin: metabolic context; insulin resistance suppresses testosterone.