Is my testosterone low?
One number on one morning isn't a diagnosis. Here's how low testosterone is actually confirmed, what the parts of your lab report mean, and what to ask for next.
The short answer
- Below 300 ng/dL on total testosteroneThat's the cutoff the AUA uses to support a diagnosis.
- On two separate morningsBlood drawn early in the day, on different days. Many single low results come back normal.
- Plus symptoms or signsLow numbers without symptoms, or symptoms without low numbers, don't make the diagnosis.
What counts as low
Total testosterone is measured in nanograms per deciliter (ng/dL) at most US labs, or nanomoles per liter (nmol/L) elsewhere. To convert, multiply nmol/L by 28.8. The AUA uses 300 ng/dL (about 10.4 nmol/L) as a reasonable cutoff.
Your lab's printed reference range may differ slightly; ranges vary by lab and assay. Values between 300 and 400 are where free testosterone is most useful.
Your lab report may flag a different lower limit, such as 264 or 250 ng/dL. Those ranges come from the lab's own reference population. Your doctor will weigh both, together with how you feel.
Why timing matters
Testosterone follows a daily rhythm. It's highest in the early morning and falls through the day. In younger men the afternoon level can be noticeably lower than the morning one, so an afternoon test can make a normal level look low. The rhythm flattens with age but doesn't disappear.
Shape of the daily testosterone rhythm, simplified for illustration. Not drawn to a numeric scale.
How to get an accurate test
- Draw before 10 AM. If you work nights, test shortly after you wake from your main sleep.
- Fast if you can. A large meal, especially a sugary one, can lower testosterone for a few hours.
- Skip testing when you're sick, after a night of very little sleep, or after a heavy night of drinking. All of these temporarily lower the level.
- Repeat on a different day before any treatment decision. Day-to-day variation is large enough that one low result is often normal the next time.
Symptoms and signs that count
Low testosterone causes symptoms, but most of these symptoms have other causes too, like poor sleep, depression, thyroid problems, diabetes or medicines. That's why the number and the symptoms both need to line up.
Total vs. free testosterone
Most testosterone in your blood is attached to proteins. About half to two-thirds is tightly bound to SHBG (sex hormone-binding globulin) and isn't available to your body. Most of the rest is loosely bound to albumin. Only about 2% floats free.
Total testosterone measures all of it. That works well for most men. But when SHBG is unusually high or low, the total can mislead:
| SHBG is… | Common reasons | Effect on your total |
|---|---|---|
| Low | Extra weight, type 2 diabetes, some steroid use | Total can look low while free testosterone is normal |
| High | Older age, liver disease, overactive thyroid, HIV, some seizure medicines | Total can look normal while free testosterone is low |
Free testosterone measured directly by many labs (the "analog" immunoassay) isn't reliable. The better options are equilibrium dialysis, or a calculated free testosterone from total testosterone, SHBG and albumin. Try it below.
Free testosterone calculator
Example values shown. Uses the Vermeulen equation. Below about 65 pg/mL (6.5 ng/dL) is a commonly used cutoff for low; labs and guidelines vary.
Who should get tested
Testing makes sense if you have symptoms. The AUA also suggests checking testosterone, even without symptoms, in men with:
If your level is low: the next tests
Once two morning tests are low, the question becomes why. A few more blood tests answer it, and some need to happen before any treatment starts.
| Test | Why it's ordered | When |
|---|---|---|
| LH | Tells a testicle problem (LH high) from a brain-signal problem (LH low or normal) | Everyone with low testosterone |
| Prolactin | A high level can point to a pituitary growth or a medicine effect | When LH is low or normal |
| Hematocrit | Baseline blood count; testosterone therapy raises it | Before starting treatment |
| PSA | Checks the prostate before treatment | Men over 40 before starting |
| Estradiol | Explains breast tenderness or growth | If you have breast symptoms |
| Semen analysis, FSH | Guides treatment that protects fertility | If you want children now or later |
Common questions
Is low testosterone just part of getting older?
Levels drift down slowly after 40, roughly 1% a year on average. But most older men stay above 300 ng/dL. A clearly low level usually has another contributor, like weight, sleep apnea, diabetes or medicines, and those are worth finding.
My first test was low and the second was normal. Which is right?
Both are real measurements; your level varies day to day. Doctors usually go by the pattern. A third morning test, plus SHBG for a calculated free testosterone, typically settles it.
Can I use an at-home testosterone kit?
Finger-prick kits can be a reasonable first look, but results should be confirmed with a standard morning blood draw at a lab before any treatment decision. Check the kit's collection timing instructions.
Should I stop supplements before testing?
Biotin, found in many hair and nail supplements, can interfere with some hormone tests. Stopping it 2 to 3 days before the draw is a common recommendation. Tell your doctor about anything else you take.
I'm already on testosterone. What should my level be?
The AUA aims for 450 to 600 ng/dL on treatment. When to draw depends on the type: just before the next dose for injections, a few hours after applying gel. Ask your prescriber for the right timing.
Check your own numbers
Enter your results or upload your lab PDF. My Testosterone Levels shows whether your level counts as low, the likely cause and your options, in your browser.
Open the My Testosterone Levels checkerSources
- Mulhall JP, Trost LW, Brannigan RE, et al. Evaluation and Management of Testosterone Deficiency: AUA Guideline. J Urol 2018;200:423–432. Reviewed and validity confirmed 2024.
- Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab 2018;103:1715–1744.
- Vermeulen A, Verdonck L, Kaufman JM. A critical evaluation of simple methods for the estimation of free testosterone in serum. J Clin Endocrinol Metab 1999;84:3666–3672.