Frequently asked questions about testosterone
What time of day is testosterone highest?
In the morning, on waking: in young men, it is clearly higher in the morning than in the evening. This gap shrinks with age (Brambilla, 2009).
Why test testosterone in the morning?
Because it varies through the day: a blood test in the evening can give a falsely low number. Guidelines advise testing in the morning, fasting, and confirming a low number with a 2nd blood test (Bhasin, 2018).
At what age does testosterone start to decline?
Slowly and steadily throughout adult life: in 890 men followed for years, total testosterone fell by about 0.12 nmol/L per year (Harman, 2001), or roughly 0.6% per year for a man starting at 20 nmol/L (our calculation). The decline varies a lot from one man to another and also depends on weight and health.
Do baby boys have a testosterone peak?
Yes: it is called “mini-puberty.” Between 1 and 3 months, a baby boy's testosterone rises almost to adult levels, then falls again before 6 months (Kuiri-Hänninen, 2014).