What you've heard: Every man over forty should be on testosterone
Should men take testosterone after 40?
False. Evidence grade: Strong.
Published Updated
The "What you've heard" box in Chapter 16
False
The evidence
Levels drift down slowly, and partly with weight and health, and only a minority of men meet the diagnosis of symptoms plus repeated low tests. In trials the benefits are modest and mostly sexual: more desire and activity, a little more energy, corrected anemia. The costs are real: switched-off sperm production, thicker blood, higher blood pressure, irregular heartbeat, clots in the lungs and more fractures. The US label still limits its use for age-related decline, and the Endocrine Society has warned against treating normal aging as disease.24 Test properly, fix weight first, and treat a confirmed deficiency with a clinician who will monitor you.
Where the book tests it
Related claims
- Can an epigenetic age test tell you how fast you are aging?Not reliable for individuals.Evidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.
- Do NAD+ supplements work?Unsupported so far.Evidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.
Sources
The "What you've heard" box in Chapter 16
- 24.Lincoff et al. 2023 and US Food and Drug Administration 2025 (note 19); Snyder et al. 2024 (note 20); Endocrine Society 2026 (note 18); Fernández-Balsells et al. 2010 (note 40).
Note numbers are those of Chapter 16, Aging Well.
This verdict is one of the "What you've heard" boxes in Chapter 16, Aging Well, where the book tests the claims people repeat against the studies behind them. The grade rates the evidence behind the verdict, by the book's stated method.
Educational content, not medical advice. Disclaimer.