Getting tested for low testosterone starts with a simple blood draw, typically done at your doctor’s office or a lab before 9 a.m. The clinical cutoff is a total testosterone level below 300 ng/dL, and confirming a diagnosis requires at least two separate blood tests taken on different days.
Symptoms That Prompt Testing
Most men seek testing because something feels off, not because they’ve hit a specific medical milestone. The symptoms that most reliably point to low testosterone include decreased sex drive, erectile problems, persistent fatigue, loss of muscle mass, increased body fat (especially around the abdomen), depressed mood, irritability, and trouble sleeping. Of these, reduced sexual desire is the single strongest predictor of genuinely low levels, outperforming longer screening questionnaires in clinical studies.
None of these symptoms on their own prove anything. They overlap with depression, poor sleep, thyroid disorders, and simply aging. That’s why blood work is essential rather than optional.
Where to Go and Who to See
Your primary care doctor can order a testosterone blood test. You don’t need a specialist to get the initial screening. If results come back low or the picture is complicated, you may be referred to a urologist or endocrinologist for further evaluation and treatment planning. Many academic medical centers also have dedicated men’s health clinics staffed by urologists who focus specifically on hormone issues.
If you’d rather skip an office visit, at-home test kits are available for roughly $70 to $220. These use a finger prick or saliva sample that you mail to a lab. However, saliva-based tests don’t track hormone changes as accurately as standard blood draws, and research into their reliability remains limited. No at-home kit can diagnose a condition or replace the follow-up testing a doctor would order. They can, at best, give you a rough number to bring to a conversation with your provider.
How to Prepare for the Blood Draw
Timing matters more than almost anything else. Testosterone peaks in the early morning and drops as the day goes on. For men under 45, the difference can be dramatic: levels drawn after 9 a.m. averaged 150 to 200 ng/dL lower than those drawn between 7 and 9 a.m. in one large study. That gap alone could push a normal reading into the “low” range or vice versa. Clinical guidelines recommend drawing blood between 8 and 11 a.m., with earlier being better, especially for younger men.
The good news is that fasting probably isn’t necessary. While some older recommendations suggest it (since eating may temporarily suppress testosterone), a clinical study comparing fasting and non-fasting samples found no significant difference in levels. Still, some labs or doctors may ask you to fast for other tests being drawn at the same time, like blood sugar or cholesterol panels, so confirm with your provider beforehand.
One practical detail worth knowing: opioid pain medications and statins (commonly prescribed cholesterol drugs) can lower testosterone levels. If you take either, mention it before testing so your doctor can interpret results in context.
What Happens During Testing
The test itself is a standard blood draw from a vein in your arm. Results typically come back within a few days. The first number you’ll see is total testosterone, which measures all the testosterone in your blood, both the portion bound to proteins and the small fraction circulating freely.
If your total testosterone is below 300 ng/dL, your doctor will order a second test on a different day to confirm. This isn’t bureaucratic caution. Testosterone fluctuates day to day based on sleep, stress, illness, and other factors. A single low reading doesn’t establish a pattern. The diagnosis of low testosterone requires two separate low results from morning blood draws.
Total vs. Free Testosterone
Most testosterone in your blood is bound to proteins and essentially unavailable. Only about 2 to 3 percent circulates freely, and this free testosterone is what your body actually uses for building muscle, maintaining bone density, and supporting sexual function. A total testosterone test captures everything. A free testosterone test measures only the usable portion.
Free testosterone testing is less common as an initial screen, but your doctor may order it if your total testosterone is borderline (close to 300 ng/dL) or if your symptoms don’t match your total number. Some men have a normal total level but low free testosterone, which can still cause symptoms. Conditions like obesity and aging increase the proteins that bind testosterone, effectively reducing how much is available even when the total looks fine.
Follow-Up Tests After a Low Result
A confirmed low testosterone level is a starting point, not the full picture. Your doctor will want to know why levels are low, because the cause determines the treatment. The key follow-up tests measure two hormones produced by the pituitary gland in the brain: LH and FSH. These hormones signal the testes to produce testosterone.
If LH and FSH are high, it means the brain is sending strong signals but the testes aren’t responding. This is called primary hypogonadism, and it points to a problem in the testes themselves, whether from injury, infection, genetic conditions, or aging. If LH and FSH are low or normal despite low testosterone, the problem is upstream in the brain or pituitary gland. This is secondary hypogonadism, and it can be caused by pituitary tumors, head injuries, certain medications, or conditions like obesity and sleep apnea.
This distinction matters because secondary hypogonadism sometimes has a reversible cause. Treating sleep apnea, losing weight, or stopping a medication may restore testosterone levels without hormone therapy. Your doctor may also check prolactin levels, thyroid function, and iron stores depending on the clinical picture.
What a Normal vs. Low Result Looks Like
The American Urological Association uses 300 ng/dL as the diagnostic threshold. Above that, you’re considered within normal range even if you’re on the lower end. Below it, combined with symptoms, you meet the criteria for testosterone deficiency.
Keep in mind that “normal” covers a wide range, roughly 300 to 1,000 ng/dL depending on the lab. A 35-year-old at 310 ng/dL is technically normal but may feel very different from one at 600 ng/dL. Context matters. Your doctor should weigh your symptoms alongside the number rather than treating the lab value as the sole deciding factor. If your level is borderline and you have significant symptoms, free testosterone testing and further workup are reasonable next steps.