A healthy adult man typically has a total testosterone level between 240 and 950 ng/dL (nanograms per deciliter), though the most commonly cited range is 300 to 800 ng/dL. That’s a wide spread, and where you fall within it depends on your age, the time of day your blood is drawn, and individual factors like body weight and genetics.
Normal Testosterone Ranges by Age
Testosterone peaks in the late teens and early twenties, then begins a slow, steady decline. A man in his twenties might have total testosterone anywhere from roughly 525 to 950 ng/dL at the upper end, while a man in his seventies could see levels closer to 328 to 720 ng/dL. The drop isn’t dramatic year to year, but it adds up over decades. Most estimates put the decline at about 1 to 2 percent per year starting around age 30.
The American Urological Association uses 300 ng/dL as the threshold below which testosterone is considered low. Other medical societies set that line slightly differently, ranging from 230 to 350 ng/dL. Falling below these levels on two separate morning blood draws, combined with symptoms, is what doctors use to diagnose testosterone deficiency.
Total vs. Free Testosterone
The number most people see on a lab report is total testosterone, which includes all the testosterone in your blood. But most of that testosterone isn’t actually available for your body to use. The majority is bound to a protein called SHBG (sex hormone-binding globulin), which is made in the liver. Testosterone locked onto SHBG can’t enter your cells or do anything useful.
A smaller portion binds loosely to another protein called albumin. This fraction can still enter tissues and contribute to testosterone’s effects on muscle, bone, and energy. The truly unbound portion, called free testosterone, makes up only about 2 to 3 percent of the total. Free testosterone is the fraction that’s immediately active in your body.
This is why two men with the same total testosterone can feel very different. If one has high SHBG levels, more of his testosterone is locked up and unavailable. If the other has low SHBG, more of his testosterone is free and working. When symptoms don’t match total testosterone numbers, doctors sometimes order free testosterone or SHBG tests to get a clearer picture.
Why Levels Change Throughout the Day
Testosterone follows a predictable daily rhythm. Levels peak in the early morning, between about 7:00 and 10:00 a.m., then drop through the afternoon and evening before rising again overnight. In younger men (ages 30 to 40), morning levels run 30 to 35 percent higher than late-afternoon levels. That’s a significant swing. A man with a total testosterone of 500 ng/dL at 8 a.m. might test closer to 325 ng/dL by 4 p.m., potentially crossing the “low” threshold purely because of timing.
This daily fluctuation shrinks with age. By 70, the morning-to-afternoon difference drops to around 10 percent, partly because the morning peak itself is lower. Because of this rhythm, labs set their normal reference ranges based on early morning blood draws. If you get tested at 2 p.m., your result won’t be directly comparable to those standard ranges.
What Affects Your Levels
Body weight is one of the strongest modifiable factors. Higher body fat is consistently linked to lower testosterone, partly because fat tissue converts testosterone into estrogen and partly because excess weight raises SHBG and insulin levels in ways that suppress production. This relationship works in both directions: low testosterone makes it easier to gain fat, and gaining fat further lowers testosterone.
Sleep matters more than most people realize. The majority of daily testosterone release happens during sleep, so consistently getting fewer than six hours can measurably reduce levels. Exercise, particularly resistance training, provides a short-term boost and supports healthier levels over time. Chronic stress, heavy alcohol use, and certain medications (especially opioids and corticosteroids) can all push levels down.
There’s also a generational trend worth noting. Research using national health survey data found that average testosterone levels in adolescent and young adult men declined significantly between 1999 and 2016. Rising obesity rates explain part of this trend, but the decline persisted even among men with normal BMI, suggesting other environmental or lifestyle factors are involved.
How Testosterone Is Tested
A standard testosterone test is a simple blood draw, ideally done between 7:00 and 10:00 a.m. when levels are at their daily peak. Because levels can fluctuate meaningfully from one draw to the next, a single test isn’t enough to diagnose low testosterone. The AUA recommends at least two tests, taken on separate mornings. For people with borderline-low results, a repeat test comes back in the normal range about 30 percent of the time.
Results can also vary between laboratories, since different labs use different assays and reference ranges. The Cleveland Clinic, for instance, lists the normal adult male range as 193 to 824 ng/dL, while other labs use 240 to 950 ng/dL. Your doctor will interpret your result against the specific lab’s reference range, not a universal number.
If you’re comparing results from different countries, be aware that the U.S. typically reports testosterone in ng/dL, while most other countries use nmol/L. To convert, multiply ng/dL by 0.0347. So 300 ng/dL equals roughly 10.4 nmol/L.
Signs That Levels May Be Low
Numbers alone don’t tell the whole story. Plenty of men with testosterone in the 300s feel fine, while some in the 400s have noticeable symptoms. The combination of low numbers and symptoms is what matters. Common signs of clinically low testosterone include persistent fatigue that doesn’t improve with rest, reduced sex drive, difficulty getting or maintaining erections, loss of muscle mass, increased body fat (especially around the midsection), and mood changes like irritability or low motivation.
Some of these symptoms overlap with depression, poor sleep, thyroid problems, and normal aging, which is another reason doctors rely on confirmed lab results rather than symptoms alone. If you’re experiencing several of these and your levels test below 300 ng/dL on two separate mornings, that’s when the conversation about treatment typically begins.