You can check your testosterone level with a simple blood test, either ordered by your doctor or purchased directly through an online lab service. The standard approach is a total testosterone blood draw taken between 8:00 and 9:00 in the morning, when your levels are at their daily peak. Getting accurate results depends on timing, preparation, and knowing which type of test you actually need.
Types of Testosterone Tests
There are three versions of the test, and they measure different things. A total testosterone test is the most common starting point. It captures all the testosterone in your blood, both the portion bound to proteins and the small amount floating freely. Most doctors will order this one first.
A free testosterone test measures only the unbound testosterone circulating in your blood. This is the form your body can actively use to build muscle, maintain bone density, and support reproductive health. Most of your testosterone is bound to a protein called sex hormone-binding globulin (SHBG), which essentially locks it up so your body doesn’t use too much at once. A smaller portion binds loosely to another protein called albumin.
Here’s why this matters: your total testosterone could come back perfectly normal while you still have symptoms of low testosterone. That happens when too much of your testosterone is bound to SHBG, leaving too little in free form for your body to actually use. If your doctor suspects this mismatch, they may order an SHBG blood test alongside total testosterone to calculate how much free testosterone you really have. A bioavailable testosterone test, which measures free testosterone plus the loosely bound portion, is a less common third option that serves a similar purpose.
Why Morning Testing Matters
Testosterone follows a predictable daily cycle. Levels peak between 7:00 and 10:00 in the morning, drop to their lowest point in the evening, then begin climbing again overnight. In men aged 30 to 40, morning levels run 30 to 35% higher than afternoon levels. That gap narrows with age, shrinking to about 10% by age 70, but it’s still significant enough to skew results.
Current guidelines recommend drawing blood between 8:00 and 9:00 a.m. to minimize this variation. If you get tested at 3:00 in the afternoon, your result could look artificially low simply because of timing, not because anything is wrong. Schedule accordingly.
How to Prepare for the Test
Your doctor may ask you to fast for several hours beforehand, drinking only water. Not every provider requires this, so follow whatever instructions you’re given. Beyond fasting, one preparation step that often gets overlooked involves biotin supplements.
Biotin (vitamin B7) is found in many hair, skin, and nail supplements, sometimes at doses of 5 to 10 mg or higher. Even a single dose can interfere with the lab equipment used to measure testosterone, producing a falsely elevated result. If you take a standard biotin supplement (5 to 10 mg), stop at least 8 hours before your blood draw. If you’re on high-dose biotin therapy of 100 mg or more per day, you need to stop at least 72 hours before testing. Check your multivitamin label too, since many contain biotin.
Where to Get Tested
The most straightforward path is through your primary care doctor or a urologist. They’ll order the blood work, send you to a lab, and interpret the results in the context of your symptoms. If your first result comes back low, expect to be tested again on a separate day. The American Urological Association requires two low readings on two different mornings before diagnosing testosterone deficiency.
If you’d rather skip the initial doctor visit, direct-to-consumer lab services let you order a testosterone test online. Labcorp OnDemand, for example, sells a comprehensive testosterone panel that you purchase on their website. An affiliated healthcare provider reviews and approves the order remotely, and you visit a local Labcorp location for the blood draw. Results are delivered to an online patient account. Other companies like Quest Diagnostics offer similar services. Some at-home collection kits also exist, though a standard venous blood draw at a lab is generally more reliable.
Keep in mind that direct-to-consumer results still need interpretation. A number on a screen doesn’t tell you whether treatment is warranted, especially since testosterone levels vary by age, time of day, and individual health factors.
Understanding Your Results
The commonly cited threshold for low testosterone in men is 300 ng/dL, the cutoff endorsed by the American Urological Association. But that single number doesn’t capture the full picture. Research from the Journal of Urology provides more nuanced, age-specific ranges for men aged 20 to 44:
- Ages 20 to 24: 409 to 558 ng/dL (normal middle range)
- Ages 25 to 29: 413 to 575 ng/dL
- Ages 30 to 34: 359 to 498 ng/dL
- Ages 35 to 39: 352 to 478 ng/dL
- Ages 40 to 44: 350 to 473 ng/dL
Notice that what counts as “normal” shifts downward with age. A 25-year-old with a total testosterone of 380 ng/dL is below the typical range for his age group, even though he’s technically above the 300 ng/dL clinical cutoff. A 42-year-old with the same reading falls within normal range. This is why age-adjusted context matters more than a single pass/fail number.
For women, testosterone is typically measured in much smaller quantities and interpreted differently. Your provider will use female-specific reference ranges, which vary by lab.
What Can Throw Off Your Results
Beyond biotin and time of day, several factors can temporarily shift your testosterone reading. Poor sleep, high stress, obesity, heavy alcohol use, and acute illness can all suppress levels. Certain medications, including opioids and some corticosteroids, lower testosterone as well. If you get a low result during a period of unusual stress or illness, that single reading may not reflect your baseline.
This is exactly why guidelines call for two separate morning tests before drawing conclusions. One low reading could be a bad night’s sleep. Two low readings, taken weeks apart under proper conditions, are far more meaningful. If both come back below the threshold and you’re experiencing symptoms like persistent fatigue, reduced sex drive, or loss of muscle mass, that’s when a conversation about treatment makes sense.