Testosterone After 40: What Normal Actually Looks Like

Most men over 40 who ask about testosterone have already decided the answer is “low.” That’s usually the wrong place to start. The real data on age and testosterone is messier than the supplement ads make it sound. Getting the right number matters more than just getting a number.

The decline isn’t as universal as it sounds

You’ve probably heard that testosterone drops 1-2% every year after 30. A 2014 study looked at testosterone levels in thousands of men and found something different: levels vary a lot more from person to person as men age, but there’s no steady, guaranteed decline after 40 once you factor in body composition and overall health.^[1] A 2023 follow-up study found the same thing — once researchers accounted for conditions like obesity, diabetes, and heart disease, age on its own stopped predicting a drop in testosterone.^[2]

In other words: your testosterone at 50 has more to do with your health than your birthday. That’s good news, because you can’t change your birthday — but you can work on body composition, sleep, and metabolic health.

What “normal” actually means on a lab report

The Endocrine Society, the main group that sets medical guidelines on this topic, published guidance in 2018 that most doctors still follow. It says a diagnosis of low testosterone (called hypogonadism) requires two things together: a consistently low lab number and symptoms.^[3] A low number by itself, with no symptoms, isn’t enough for a diagnosis — and the guideline specifically says doctors shouldn’t screen men who have no symptoms in the first place.

Here’s what that means in practice, before you get tested:

• Doctors usually look for total testosterone under about 300 ng/dL, confirmed on two separate morning blood draws — not one afternoon test.
• You also need symptoms: lower sex drive, unexplained tiredness, loss of muscle, or mood changes. A low number with none of these symptoms usually isn’t something to treat.

Why the symptom-first approach matters

This is the part that “low T” marketing leaves out. Tiredness, low sex drive, and muscle loss at 45 can come from several different causes — poor sleep, chronic stress, thyroid problems, or depression can all look like low testosterone. A blood test exists to figure out which one it actually is, not to confirm a story you’ve already decided is true. If you’re going to get tested, do it because something specific changed for you — not just because you had a birthday.

The actual protocol

1. Track the symptom, not the age. Write down when you noticed a change in libido, energy, or strength — and whether anything else in your life changed at the same time.
2. Get two morning blood draws, not one. Testosterone rises and falls through the day and peaks in the morning. A single afternoon result won’t tell you much.
3. Ask for free testosterone along with total. A protein called SHBG (sex hormone-binding globulin) rises with age and “locks up” some of your testosterone. That can make your total number look low even when the active, usable amount is fine.
4. Rule out other causes first. Sleep apnea, uncontrolled diabetes, and obesity all lower testosterone on their own, separate from aging. Treating those often moves your number more than testosterone treatment would.

None of this means testosterone replacement therapy is the wrong choice for some men. It just means the decision should come from a real diagnostic process — not a feeling that 45 is supposed to feel worse than 35.

References

[1] Yeap BB, et al. “A Validated Age-Related Normative Model for Male Total Testosterone Shows Increasing Variance but No Decline after Age 40 Years.” PLOS ONE. 2014. DOI: 10.1371/journal.pone.0109346. Finding: variance in total testosterone increases with age but the population-level decline after 40 is not consistent once modeled against body composition and health status. ↑︎

[2] Association between comorbidities and longitudinal changes in total testosterone among men from the Baltimore Longitudinal Study of Aging. The Journal of Sexual Medicine. 2023. DOI: 10.1093/jsxmed/qdad025. Finding: when adjusted for comorbidities (obesity, diabetes, cardiovascular disease), age does not independently predict a significant decline in testosterone level. ↑︎

[3] Bhasin S, et al. “Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline.” Journal of Clinical Endocrinology & Metabolism. 2018;103(5):1715-1744. DOI: 10.1210/jc.2018-00229. Finding: diagnosis requires consistently low testosterone plus symptoms; routine population screening is not recommended. ↑︎

Kurt Greiner

Kurt is a digital strategist and IT professional blending emerging technology with practical application to help businesses and individuals streamline their digital presence. His current work focuses on the intersection of intentional living and technological resilience, exploring how individuals can leverage modern tools to navigate the second half of life with purpose.