What's a normal testosterone level by age?

There isn't one magic number — and that's the first thing to understand about normal testosterone levels by age. Most labs treat a total testosterone of roughly 300–1,000 ng/dL (about 10–35 nmol/L) as the adult male range, and the American Urological Association flags anything below 300 ng/dL as low testosterone. But that range is deliberately wide, and where a healthy level sits shifts with age.

Testosterone usually peaks in the late teens and twenties, then declines slowly — often around 1% a year from the late thirties onward. So a reading that's perfectly normal at 60 might be a red flag at 25. The Endocrine Society puts the range for healthy men aged 19–39 at 264–916 ng/dL, which shows how much normal variation exists even within a single age band.

A few things most men miss. First, timing matters as much as the number — testosterone is highest in the morning, so a proper testosterone blood test is taken before 10am; an afternoon reading can make a normal man look low. Second, free testosterone — the small fraction available to your tissues — often tells you more than your total, especially if your SHBG (the protein that binds testosterone) is high. You can have a “normal” total but low free testosterone and still feel terrible. Third, symptoms matter: two men with identical numbers can feel completely different.

This is exactly why so many men are told their bloodwork is “fine” yet still feel flat, foggy, or low on drive — the standard panel often misses the fuller picture.

What to do: test in the morning, ask for free testosterone and SHBG alongside total, compare your result against an age-appropriate range rather than a single cut-off, and always read the number next to your symptoms. One borderline reading isn't a diagnosis — a clear pattern across two morning tests, combined with symptoms, is what actually points to low testosterone.