You can get a reasonable sense of whether your testosterone is healthy through a combination of a blood test and paying attention to your body. A standard blood draw measures your total testosterone, and most labs flag anything below about 300 ng/dL as low. But that single number doesn’t tell the whole story. Your physical energy, body composition, mood, sex drive, and sleep quality are all practical signals of where your testosterone stands.
What a Blood Test Actually Measures
When your doctor orders a testosterone test, the result you get back is your total testosterone. This includes all the testosterone in your blood, both the portion that’s actively working in your tissues and the portion that’s bound to proteins and essentially locked away. The problem is that total testosterone can look perfectly normal while the amount your body can actually use is too low, or vice versa.
The protein that matters most here is called SHBG (sex hormone binding globulin), produced mainly by your liver. Testosterone bound to SHBG can’t interact with your muscles, bones, or brain. Only the “free” portion, the testosterone floating unattached, is available for your body to use. If your SHBG is unusually high, you could have a normal total testosterone number yet still experience symptoms of deficiency because very little of it is free. The reverse is also true: low SHBG can mean more active testosterone than your total number suggests.
This is why getting both total testosterone and SHBG tested together gives a much clearer picture. Your doctor can then estimate your free testosterone, which research shows is a stronger predictor of muscle mass, strength, and physical function than total testosterone alone, particularly as you get older.
When and How to Get Tested
Testosterone follows a daily rhythm, peaking in the early morning and dropping as the day goes on. If you’re under 45, this swing is significant. Men under 40 can see levels drop by more than 200 ng/dL between an early-morning draw and one taken later in the day. That’s enough to turn a normal result into a falsely low one. For this reason, men under 45 should have blood drawn between 7 a.m. and 9 a.m.
If you’re 45 or older, the daily fluctuation shrinks considerably, and testing anytime before 2 p.m. is generally acceptable.
One important caveat: up to 30% of men who test low on their first draw will come back normal on a repeat test. Illness, poor sleep the night before, stress, and even a heavy meal can temporarily suppress your levels. A single low result is not a diagnosis. Any low reading should be confirmed with a second morning test before drawing conclusions.
Physical Signs of Healthy Testosterone
Your body gives you ongoing feedback about your hormonal health if you know what to look for. Healthy testosterone supports a specific set of physical functions, and when those are working well, it’s a good sign your levels are in a solid range.
- Muscle maintenance: You can build and retain muscle with regular resistance training. One of the hallmark signs of declining testosterone is losing muscle mass despite consistent exercise, or gaining body fat (especially around the midsection) without changes in diet.
- Bone density: Testosterone keeps bones strong. While you won’t feel this day to day, unexplained fractures or a bone density scan showing thinning can point to long-term deficiency.
- Body and facial hair: A noticeable reduction in body or facial hair growth over time can signal dropping levels. This is different from normal male pattern baldness on the scalp, which is driven by a different hormonal process.
- Sexual function: Reliable erections, particularly morning erections, are one of the most practical everyday indicators of adequate testosterone. A consistent absence of morning erections is worth paying attention to. Healthy libido is another strong signal.
- Energy levels: Persistent fatigue that doesn’t improve with better sleep or reduced stress is a common symptom of low testosterone, though it overlaps with many other conditions.
None of these signs in isolation confirms a testosterone problem. But if several of them shift at the same time, it paints a clearer picture.
Mental and Emotional Indicators
Testosterone has a well-documented influence on brain function. Healthy levels are associated with lower anxiety, more stable mood, and better concentration. When testosterone drops, many men notice irritability, difficulty focusing, and a general sense of low motivation before they notice any physical changes.
Research consistently shows that low testosterone is linked to increased depressive symptoms, especially in older men. Spatial thinking, the kind of mental skill involved in navigation and visualizing objects in three dimensions, also tends to decline alongside testosterone. In supplementation studies, restoring testosterone to normal levels improved both depressive symptoms and spatial cognitive performance.
Low libido deserves special mention because it straddles the physical and psychological. A persistently low sex drive, particularly one that represents a clear change from your baseline, is one of the most reliable subjective indicators that testosterone may be insufficient.
Why “Normal” Ranges Can Be Misleading
Most labs define the normal range for total testosterone as roughly 300 to 1,000 ng/dL. That’s an enormous spread. A 35-year-old at 310 ng/dL is technically “normal” but sitting at the very bottom of the range and may feel very different from someone at 600 ng/dL. The reference range reflects the statistical distribution across all adult men tested at that lab, not an optimal target for any individual.
Age matters too. Total testosterone declines in a fairly linear pattern as men age, but free testosterone drops even faster because SHBG rises with age. This means an older man’s total testosterone might look reasonable while his free testosterone, the portion doing the actual work, has fallen significantly. Research in older men found that free testosterone predicted lean mass, muscle strength, and physical performance, while total testosterone did not.
Context is everything. Your numbers need to be interpreted alongside your symptoms, your age, your SHBG level, and your overall health. A total testosterone of 450 ng/dL in a man with low SHBG might mean plenty of free testosterone and no symptoms at all. The same number in a man with high SHBG could mean genuine deficiency.
Factors That Suppress Testosterone
Before assuming something is clinically wrong, it’s worth checking whether lifestyle factors are dragging your levels down. Several common, reversible causes can significantly lower testosterone.
Sleep is probably the single biggest lever. Testosterone is produced primarily during sleep, and even modest sleep restriction (five to six hours per night for a week) can reduce levels by 10 to 15% in young men. Excess body fat is another major factor. Fat tissue converts testosterone into estrogen through a process called aromatization, creating a cycle where weight gain lowers testosterone and lower testosterone makes it easier to gain weight. Chronic stress keeps cortisol elevated, which directly suppresses testosterone production. Heavy alcohol use and certain medications, particularly opioids, can also blunt levels substantially.
If you address sleep, body composition, stress, and alcohol intake and your symptoms persist, that’s when a blood test becomes especially useful for distinguishing a lifestyle issue from something that may need medical attention.
Putting It All Together
The most reliable way to know if you have “good” testosterone is to combine objective data with subjective signals. Get a morning blood test that includes both total testosterone and SHBG so your free testosterone can be estimated. Then honestly assess whether the physical and mental markers line up: Are you maintaining muscle? Is your sex drive where you’d expect it to be? Do you feel mentally sharp and emotionally even? If your numbers are in a healthy range and you feel good, your testosterone is doing its job. If your numbers look fine but you’re experiencing multiple symptoms, the free testosterone estimate may reveal the gap. And if you’ve never been tested, your body’s signals alone can tell you a lot about whether it’s time to check.