What is testosterone?
Testosterone is the main male sex hormone. In men it is made mostly by the testicles; women make it in much smaller amounts. In both sexes it supports sex drive, muscle and bone; in men it also drives sperm production, body hair and red blood cell production.
Most testosterone in blood is bound to proteins, mainly SHBG and albumin. A standard total testosterone test measures bound and unbound hormone together. Free testosterone is the small unbound part that tissues can use, and it matters most when SHBG is unusually high or low.
Testosterone levels by age chart
These are reference ranges from ARUP Laboratories, measured by mass spectrometry. To convert ng/dL to nmol/L, multiply by 0.0347.
| Age | Men (ng/dL) | Men (nmol/L) | Women (ng/dL) |
|---|---|---|---|
| 14 to 15 | 31 to 733 | 1.1 to 25.4 | 6 to 52 |
| 16 to 17 | 158 to 826 | 5.5 to 28.7 | 9 to 58 |
| 18 to 39 | 300 to 1,080 | 10.4 to 37.5 | 9 to 55 |
| 40 to 59 | 300 to 890 | 10.4 to 30.9 | 9 to 55 |
| 60 and over | 300 to 720 | 10.4 to 25.0 | 5 to 32 |
MedlinePlus publishes slightly different adult ranges:
| Group | ng/dL | nmol/L |
|---|---|---|
| Men 17 to 50 | 249 to 836 | 8.6 to 29.0 |
| Men over 50 | 193 to 740 | 6.7 to 25.7 |
| Women 17 to 50 | 8.4 to 48.1 | 0.3 to 1.7 |
| Women over 50 | 2.9 to 40.1 | 0.1 to 1.4 |
ARUP Laboratories (mass spectrometry) and the Travison et al. 2017 harmonized range.
The harmonized range for men
Testosterone assays differ between labs, so in 2017 researchers calibrated four large US and European studies to the CDC's reference method. In healthy, non-obese men aged 19 to 39, the harmonized range was 264 to 916 ng/dL, with a median of 531 ng/dL. Several of the same researchers wrote the Endocrine Society's 2018 testosterone guideline. Older men and men with obesity have lower average levels.
How testosterone changes with age
Testosterone falls gradually in men from middle age. In the Baltimore Longitudinal Study of Aging, cited in the AUA guideline, the share of men with low testosterone rose from 12% in their 50s to 19% in their 60s, 28% in their 70s and 49% over 80. In women, levels fall after menopause, which is why ranges for women over 50 are lower.
What low testosterone means
The AUA uses a total testosterone below 300 ng/dL as a reasonable cut-off to support a diagnosis of low testosterone, but only after two early-morning tests on separate days, and only when there are symptoms or signs such as low sex drive, erectile problems or loss of muscle. A low number without symptoms is not a diagnosis.
MedlinePlus lists these causes of low testosterone in men:
- Problems with the testicles, including injury, infection, cancer or iron overload
- Pituitary or hypothalamus disorders, including a prolactin-producing tumor (see prolactin)
- Chronic illness, including liver and kidney disease, and low thyroid function
- Obesity and obstructive sleep apnea
- Alcohol use disorder, and overtraining
- Genetic conditions such as Klinefelter syndrome
In women, low testosterone is normal; only very low levels may point to an adrenal, pituitary or ovarian disorder. If your result is low and you have symptoms, talk to your doctor, who may check LH, FSH and prolactin to find the cause.
Worked example: 285 ng/dL at age 47
Say a 47-year-old man with low sex drive gets a total testosterone of 285 ng/dL from a blood draw at 2 p.m. That is under the AUA's 300 ng/dL cut-off and just above the harmonized lower limit of 264 ng/dL.
The first problem is timing. Levels are highest between 7 and 10 a.m., so an afternoon draw can read low, and the AUA wants two early-morning tests on separate days before calling testosterone low. Excess weight, sleep apnea, recent illness and overtraining are all on this page's list of things that lower it.
If two morning results both come back under 300, questions for the doctor: Should we check LH and prolactin to find the cause? Is my SHBG high or low enough that free testosterone would change the picture? Could my weight or sleep be part of it? If therapy comes up, what PSA check do you want first?
What high testosterone means
In men, a common reason for high testosterone is taking testosterone or anabolic steroids. MedlinePlus also lists testicular tumors and adrenal disorders such as congenital adrenal hyperplasia (CAH). In women, high testosterone may be caused by polycystic ovary syndrome (PCOS), ovarian tumors or other ovarian problems, CAH or a pituitary disorder. Signs in women include excess facial and body hair, acne and irregular periods. Our hormone test guide for women covers PCOS markers.
What can change testosterone
- Time of day. Levels are highest in the morning, between about 7 and 10 a.m.
- Body weight and sleep apnea. Both are on MedlinePlus's list of causes of low testosterone, so treating them is part of the workup.
- Illness and overtraining can lower testosterone temporarily.
- Medicines and supplements. Testosterone, anabolic steroids and some supplements raise it; tell whoever orders the test about everything you take.
- Testosterone therapy is a decision for your doctor. The Endocrine Society recommends against starting it in men planning fertility soon, and in men with prostate or breast cancer or a PSA above 4 ng/mL without further evaluation (see PSA).
How to test testosterone
- Collect between 7 and 10 a.m. The Endocrine Society recommends a fasting morning sample.
- Confirm a low result with a second morning test on another day, ideally at the same lab with the same assay (AUA).
- Test when you are well, not during an illness or after a very hard training block.
- If total testosterone is borderline, ask about SHBG and free testosterone (Endocrine Society).
Which at-home tests include testosterone
SiPhox Health measures total testosterone on four panels, with some sex differences:
| SiPhox panel | Testosterone markers | Who |
|---|---|---|
| Longevity Essentials | Total and free (calculated) testosterone, SHBG | Men |
| Hormone Focus | Total, free and % free testosterone, SHBG, free androgen index | Men and women |
| Ultimate 360 | Same as Hormone Focus plus 48 other markers | Men and women |
| GLP Optimization | Total and free testosterone, SHBG | Total T for men |
Men get testosterone on the default Longevity Essentials panel, included in the base $124 a test. Women need Hormone Focus or Ultimate 360 for testosterone. Collect your SiPhox sample in the morning, fasting, so it compares with guideline ranges. See our at-home testosterone test guide for other kits.
A note on home samples: SiPhox's partner lab tests capillary blood collected from the upper arm. SiPhox says its results show a 95% to 99% correlation with venous draws in its own quarterly comparisons against Labcorp and Quest, but it has not published a study of the EasyDraw device. If a result would change a treatment decision, confirm it with a venous test through your doctor.
Longevity Essentials
The default panel: heart, metabolic, hormone and inflammation markers in one draw.
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Hormone Focus
Sex hormones for men and women, including PSA for men and progesterone for women.
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Ultimate 360
Everything on the four core panels plus iron studies, B12 and folate, GGT and PSA.
Check priceFrequently asked questions
What is a normal testosterone level for a man by age?
ARUP's ranges are 300 to 1,080 ng/dL at 18 to 39, 300 to 890 ng/dL at 40 to 59 and 300 to 720 ng/dL from 60. The harmonized range for healthy men aged 19 to 39 is 264 to 916 ng/dL.
What testosterone level is considered low?
The American Urological Association uses under 300 ng/dL, confirmed on two early-morning tests and combined with symptoms. The Endocrine Society's harmonized lower limit is 264 ng/dL.
What is a normal testosterone level for a woman?
About 8.4 to 48.1 ng/dL for women aged 17 to 50 and 2.9 to 40.1 ng/dL over 50 (MedlinePlus). ARUP uses 9 to 55 ng/dL before menopause and 5 to 32 ng/dL after.
What is 300 ng/dL in nmol/L?
About 10.4 nmol/L. Multiply ng/dL by 0.0347 to convert to nmol/L, or divide nmol/L by 0.0347 to get ng/dL.
What time of day should I test testosterone?
Between 7 and 10 a.m., when levels are highest, and fasting if possible. Always retest at the same time of day.
Sources
- American Urological Association: Evaluation and management of testosterone deficiency guideline
- Bhasin S et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2018
- Travison TG et al. Harmonized reference ranges for circulating testosterone levels in men. J Clin Endocrinol Metab 2017
- ARUP Laboratories Test Directory: Testosterone, free and total, with SHBG
- ARUP Laboratories Test Directory: Testosterone (adult males)
- MedlinePlus Medical Encyclopedia: Testosterone
- MedlinePlus Lab Tests: Testosterone levels test
- SiPhox Health: panel comparison (checked 29 Sep 2026)
- SiPhox Health: Longevity Essentials panel
- SiPhox Health: Hormone Focus panel