It took a median 3.4 months for sperm to come back
Across 1549 healthy men in 30 male-contraception studies, sperm concentration returned to 20 million per millilitre in a median of 3.4 months, two thirds within six.
What the study found
Every man in the contraception trials got his sperm count back
Pooling 1549 men across 30 male-contraception studies, sperm concentration returned to 20 million per millilitre in a median of 3.4 months, two thirds within six and all within twenty-four. Shorter courses and shorter-acting preparations sped that up without changing whether it happened.
The caveat · Healthy volunteers on short courses
These were healthy men with normal testosterone taking defined, mostly short courses in contraception trials, not men on open-ended replacement or on the much larger doses used for physique. Recovery was faster with shorter treatment and shorter-acting preparations, both of which cut against long-term replacement. The endpoint is a sperm concentration of 20 million per millilitre, a fertility proxy rather than a pregnancy. The data stop in 2005.
What we don't know
These were healthy men with normal testosterone taking defined, mostly short courses in contraception trials, not men on open-ended replacement or on the much larger doses used for physique. Recovery was faster with shorter treatment and shorter-acting preparations, both of which cut against long-term replacement. The endpoint is a sperm concentration of 20 million per millilitre, a fertility proxy rather than a pregnancy. The data stop in 2005.