Testosterone levels are measured with a blood test, typically drawn from a vein in your arm during the morning hours when levels peak. The most common version is a total testosterone test, which captures all the testosterone circulating in your blood. For adult men, the standard reference range is 240 to 950 ng/dL, though what counts as “normal” shifts with age and varies between labs.
Types of Testosterone Tests
There are three versions of the test, each measuring a slightly different slice of your testosterone.
Total testosterone is the default. It measures everything: testosterone floating freely in your blood plus testosterone bound to proteins. This is almost always the first test ordered. The limitation is that it can’t tell you how much of that testosterone is actually available for your body to use.
Free testosterone measures only the unattached form of the hormone. Free testosterone makes up a small fraction of your total, but it’s the form your body can readily use for building muscle, maintaining bone density, and other functions. This test is less commonly ordered but becomes important when total testosterone looks normal yet symptoms persist.
Bioavailable testosterone captures free testosterone plus testosterone loosely bound to a protein called albumin (which your body can still access fairly easily). It excludes testosterone tightly bound to a protein called SHBG, which essentially locks the hormone away. This test is the least common of the three.
Why SHBG Matters for Your Results
SHBG (sex hormone-binding globulin) is a protein made mostly in your liver that binds to testosterone and controls how much of it stays active. When SHBG levels are high, more of your testosterone is locked up and unavailable to your tissues. You could have a total testosterone reading that looks perfectly fine while your body is functionally starved of the hormone. The reverse is also true: low SHBG means more of your testosterone is free and active, even if your total number seems modest.
This is why providers sometimes order an SHBG test alongside total testosterone. Comparing the two gives a much clearer picture of how much testosterone your body can actually use. Conditions like obesity, type 2 diabetes, thyroid disorders, and liver disease all shift SHBG levels and can make a total testosterone result misleading on its own.
How to Prepare for the Test
Testosterone follows a daily rhythm, peaking in the early morning and declining through the afternoon. For this reason, blood draws are typically scheduled in the morning. The Endocrine Society specifically recommends measuring morning fasting total testosterone when diagnosing low levels.
Fasting isn’t always strictly required, but eating can influence results, and most guidelines call for it when confirming a diagnosis. If you take high-dose biotin supplements (5 mg or more per day, commonly sold for hair and nail health), stop them at least one week before your test. Biotin interferes with the type of lab analysis used for testosterone and can produce falsely elevated readings. Certain anabolic compounds, including nandrolone, also cause falsely high results. Let your provider know about any supplements or medications you’re taking before the draw.
What Normal Ranges Look Like
For men 19 and older, Mayo Clinic Laboratories lists total testosterone at 240 to 950 ng/dL. Free testosterone ranges are narrower and decline steadily with age. A man in his 20s might have a free testosterone between 5.25 and 20.7 ng/dL, while a man in his 60s would typically fall between 3.67 and 13.9 ng/dL. By age 80, the expected range drops to roughly 2.88 to 10.5 ng/dL.
Bioavailable testosterone follows the same downward slope. Men in their 20s range from about 83 to 257 ng/dL, dropping to 40 to 168 ng/dL by the 60s. These gradual declines are a normal part of aging, not automatically a sign of a problem. What matters is whether your levels match your symptoms.
Women produce testosterone too, in much smaller amounts. Testing in women is typically ordered when there are signs of excess androgens (unusual hair growth, irregular periods, or fertility issues) or low androgens (decreased libido). For women, even a total testosterone within the reference range doesn’t always rule out a problem. Free or bioavailable testosterone may still be abnormal, so providers often check multiple measures.
Why You’ll Likely Need More Than One Test
Testosterone fluctuates from day to day based on sleep, stress, illness, and other factors. A single blood draw only captures one moment. The Endocrine Society guidelines call for confirming low testosterone by repeating the morning fasting measurement on a separate day. A diagnosis of hypogonadism (clinically low testosterone) requires both consistent symptoms and “unequivocally and consistently low” levels across multiple tests. One low reading on its own isn’t enough.
Your provider will also typically do a physical exam and review your medical history and medications before ordering the test. If total testosterone comes back low, follow-up tests might include free testosterone, SHBG, and hormones from the pituitary gland to figure out where the problem originates.
At-Home Test Kits vs. Lab Draws
Mail-order testosterone kits have become widely available. Most use a finger-prick blood sample or a saliva collection that you send to a lab. They’re convenient and can give you a general snapshot, but they come with real limitations.
Saliva tests measure free testosterone specifically, which is useful in theory. Research has shown a strong correlation between saliva and blood serum testosterone under controlled conditions, with correlation coefficients above 0.85 in several studies. But saliva testing doesn’t always track changes in hormone levels as quickly or accurately as blood tests, and a 2020 review noted a lack of robust research on saliva collection methods. The studies showing good accuracy were conducted in young, healthy, trained men, so results may not generalize to everyone.
Finger-prick kits measure from a small blood sample, but the collection process can be messy and difficult. The small tube size makes it easy to provide an inadequate sample. More importantly, no at-home kit can diagnose an underlying condition. They can’t replace the repeated, timed, fasting blood draws that clinical guidelines require for a formal diagnosis. If an at-home result concerns you, it’s a starting point, not an endpoint. You’ll still need a standard venous blood draw to confirm anything actionable.
What the Test Involves
The clinical blood draw itself is straightforward. A technician ties a band around your upper arm, inserts a small needle into a vein (usually at the inside of your elbow), and fills one or two tubes. The whole process takes under five minutes. You might feel a brief sting and have mild soreness or a small bruise afterward, but complications are rare. Results typically come back within a few days, depending on the lab.