Testosterone levels refer to the amount of testosterone circulating in your bloodstream, measured through a simple blood test. For adult men, the normal range falls between 193 and 824 ng/dL (nanograms per deciliter). For adult women, the normal range is much lower, between 8 and 60 ng/dL. These numbers matter because testosterone plays a central role in muscle mass, bone density, sex drive, mood, and energy in both sexes.
What Testosterone Does in Your Body
Testosterone is the primary sex hormone in males, produced mainly in the testes. Women also produce it in smaller amounts through their ovaries and adrenal glands. In men, it drives the development of male physical traits during puberty and continues to regulate muscle strength, fat distribution, red blood cell production, and sperm count throughout life. In women, testosterone contributes to bone strength, ovarian function, and libido.
Not all testosterone in your blood is equally active. Most of it is bound to proteins, primarily one called sex-hormone-binding globulin (SHBG) and another called albumin. When testosterone is bound to these proteins, your body can’t easily use it. A smaller fraction circulates freely, unattached to any protein, and this “free testosterone” is the form most available for building bones and muscles and carrying out other functions.
Normal Ranges by Sex and Age
The standard reference range for total testosterone in adult males (ages 18 to 99) is 193 to 824 ng/dL. This is a wide range because testosterone varies significantly from person to person based on age, genetics, body composition, and time of day. For adult women aged 19 and older, the typical range is 8 to 60 ng/dL.
It’s worth knowing that testosterone gradually declines in men starting around age 30, typically dropping about 1% per year. This is a normal part of aging, not necessarily a medical condition. The key distinction is whether levels drop low enough to cause symptoms. Lab reference ranges can also vary slightly depending on the testing method and laboratory, so your results should always be interpreted against the specific range printed on your lab report.
How Testosterone Is Tested
A total testosterone test is the most common type ordered. It measures both bound and free testosterone combined. In some cases, a doctor may also order a free testosterone test, which measures only the unattached form. This can be useful when total testosterone falls in a borderline range but symptoms are present, since someone with normal total testosterone could still have low free testosterone if their binding proteins are elevated. A third option, a bioavailable testosterone test, measures free testosterone plus testosterone loosely bound to albumin, though this is less commonly ordered.
Timing matters. Testosterone follows a daily rhythm, peaking in the early morning and dropping through the afternoon. In men younger than 45, this swing is significant: levels average around 600 ng/dL at 7 a.m. but fall to 400 to 450 ng/dL by 2 p.m. That’s a 25% to 33% drop over the course of a single day. This is why guidelines recommend drawing blood before 10 a.m. for the most accurate reading. In men older than 45, this daily fluctuation becomes less pronounced, so timing is somewhat less critical.
A single low reading isn’t enough for a diagnosis. Because levels fluctuate day to day, doctors typically require at least two separate morning blood draws showing consistently low results before diagnosing a deficiency.
Symptoms of Low Testosterone in Men
The most telling symptoms are sexual. Low libido, loss of morning or spontaneous erections, and difficulty attaining or maintaining an erection are the signs most strongly linked to testosterone deficiency. Other symptoms that point strongly toward low testosterone include loss of body hair (particularly armpit and pubic hair), shrinking testicles, hot flashes, and low or zero sperm count.
Beyond the sexual symptoms, low testosterone can show up as increased body fat, decreased muscle strength and mass, reduced endurance, depressed mood, and problems with concentration and memory. Some men develop enlarged breast tissue. The challenge is that many of these symptoms overlap with other conditions like depression, thyroid disorders, or simply poor sleep, which is why blood testing is necessary to confirm the cause.
High Testosterone in Women
While low testosterone gets more attention in men, elevated testosterone is a common concern for women. The most frequent cause is polycystic ovary syndrome (PCOS), which can raise both total and free testosterone levels. Symptoms of excess testosterone in women include acne and oily skin, excess body hair growth on the face and body (hirsutism), irregular periods, infertility, and male-pattern hair thinning.
The adrenal glands can also overproduce testosterone in women. If symptoms like these appear gradually over months or years, PCOS or an adrenal condition is the likely explanation. However, if these changes develop rapidly and suddenly, the cause may be more serious, such as a hormone-producing tumor, and warrants prompt medical evaluation.
What Affects Your Levels
Several everyday factors push testosterone up or down independently of any medical condition.
Body weight is one of the strongest influences. Being overweight or obese is consistently linked to lower testosterone, and losing weight can significantly raise levels, especially in people with more to lose. The relationship works both ways: low testosterone promotes fat accumulation, and excess fat tissue actively converts testosterone into estrogen, creating a cycle that can be hard to break without intentional weight management.
Sleep has a surprisingly large effect. In one study of young men, restricting sleep to five hours per night for just one week reduced daytime testosterone by 10% to 15%. Testosterone production depends heavily on deep sleep cycles, so chronic sleep deprivation or poor sleep quality can meaningfully suppress levels over time.
Chronic illness also plays a role. Conditions affecting the testes, pituitary gland, or hypothalamus, whether from injury, infection, or cancer treatment, can directly impair testosterone production. There’s also a well-established link between diabetes and testosterone: men with diabetes are more likely to have low testosterone, and men with low testosterone are more likely to develop diabetes later on.
Other factors include high stress (which raises cortisol and can suppress testosterone production), heavy alcohol use, and certain medications like opioids and corticosteroids. Even something as simple as the time of year or acute illness can temporarily shift your numbers.
Total vs. Free Testosterone: Which Matters More
For most initial evaluations, total testosterone is the standard measurement. It gives a reliable picture for the majority of people. Free testosterone becomes more useful in specific situations: when total testosterone is borderline (close to the lower cutoff but not clearly below it), when someone has conditions that alter binding protein levels (such as obesity, aging, liver disease, or thyroid disorders), or when symptoms are present despite normal-looking total testosterone.
Free testosterone typically makes up only about 2% to 3% of total testosterone. Because the amount is so small, it’s harder to measure accurately, which is one reason it’s not the default test. When ordered, it’s often calculated from total testosterone and SHBG levels rather than measured directly, since the calculation can be more reliable than some direct assays.