Men’s testosterone levels typically begin declining around age 40, dropping roughly 1% per year from that point forward. This isn’t a sudden loss. It’s a slow, steady slide that most men never notice, though some eventually cross into territory where symptoms become hard to ignore.
When the Decline Starts
Testosterone production peaks in late adolescence and early adulthood, generally holding steady through a man’s 30s. After 40, levels begin a gradual descent of about 1% annually. That may sound small, but it compounds. By age 60, a man’s testosterone could be 20% lower than it was at 40. By 70, it could be down 30% or more.
The reference ranges tell the story clearly. Men in their 40s typically fall between 252 and 916 ng/dL. By their 50s, the range shifts to 215 to 878 ng/dL. In their 60s, it’s 196 to 859 ng/dL, and by their 70s, 156 to 819 ng/dL. Notice how the floor keeps dropping with each decade. That widening gap at the bottom is where problems tend to emerge.
Because the average decline is just 1% per year, most older men still retain levels in the normal range. Low testosterone (defined as below 300 ng/dL) affects more than 20% of men in their 60s and more than 30% of men in their 70s. So while the decline is universal, clinically low levels are not inevitable.
What Low Testosterone Feels Like
Some men with low testosterone have no noticeable symptoms at all. Others experience a mix of physical and psychological changes that can overlap with normal aging, making them easy to dismiss. The most common signs include low sex drive, difficulty getting or maintaining erections, sleep problems, loss of muscle size and strength, increased body fat, bone loss, difficulty concentrating, and depression.
The tricky part is separating age-related changes from a genuine hormonal deficit. Feeling somewhat less interested in sex as you get older is normal. Having virtually no interest in sex is not. Similarly, losing some muscle mass over the decades is expected, but rapid or significant changes in body composition alongside fatigue and mood shifts point more strongly toward a hormonal cause. Conditions like high blood pressure, diabetes, and depression can also produce overlapping symptoms, which is why a blood test is the only way to know for sure.
Your Waist Size Matters More Than Your Age
Age isn’t the only factor pulling testosterone down, and it may not even be the most powerful one. Obesity accelerates the decline significantly. A 2007 study of more than 1,600 men over 40 found that each one-point increase in BMI was associated with a 2% drop in testosterone. That means a man who gains enough weight to push his BMI up five points could see a 10% testosterone decline on top of whatever age-related loss he’s already experiencing.
Waist circumference turns out to be an even stronger predictor than BMI. A study of over 1,800 men found that a four-inch increase in waist size raised the odds of having low testosterone by 75%. For comparison, ten years of aging only increased those odds by 36%. Waist circumference was the single strongest predictor of developing symptoms of testosterone deficiency. In practical terms, a 45-year-old man carrying significant belly fat may have lower testosterone than a lean 60-year-old.
This means a meaningful portion of testosterone loss that gets blamed on aging is actually driven by weight gain, which is something within your control. Losing visceral fat (the kind packed around your midsection) can slow or partially reverse the decline.
How Low Testosterone Is Diagnosed
The American Urological Association defines low testosterone as a total level below 300 ng/dL. But a single blood draw isn’t enough for a diagnosis. Guidelines call for at least two separate measurements, both taken in the early morning when testosterone peaks. Levels fluctuate throughout the day, with afternoon readings sometimes coming in 20% to 30% lower than morning ones, so timing matters.
Your body also produces a protein called sex hormone-binding globulin (SHBG) that latches onto testosterone and makes it unavailable to your tissues. SHBG levels can shift with age and other health conditions, meaning your total testosterone number doesn’t always reflect how much your body can actually use. If total testosterone comes back borderline, your doctor may also check free testosterone, which measures only the unbound, active form.
When Treatment Comes Into Play
Testosterone replacement is not recommended based on age or a number alone. Medical guidelines specify that treatment should only be considered for men who have both consistently low blood levels and symptoms that match. A man with a testosterone reading of 280 ng/dL who feels fine and functions normally would not typically be a candidate. A man at 250 ng/dL with significant fatigue, erectile problems, and muscle loss would be evaluated differently.
The diagnostic process is deliberately cautious because testosterone therapy carries trade-offs, including potential effects on fertility, cardiovascular health, and red blood cell production. For men whose low levels are partly driven by modifiable factors like obesity, poor sleep, or excessive alcohol use, addressing those issues first can raise testosterone naturally and sometimes eliminate the need for medical intervention altogether.