Take D-aspartic acid supplements

Aspartic acid comes in the form of D-aspartic acid (D-AA), which is sold as a nutritional supplement. It should not be mistaken with L-aspartic acid, which is far more common than D-AA and helps to the structure of many proteins. D-AA is mostly found in certain glands, including the testicles, semen, and sperm cells.

D-AA is thought by researchers to play a role in male fertility. In fact, compared to men who are fertile, infertile men's D-AA levels are substantially lower. Studies show that D-AA supplementation may raise levels of testosterone, the male sex hormone that is essential to male fertility. For instance, one research on infertile males found that 2.7 grams of D-AA daily for three months boosted testosterone levels by 30–60% and sperm count and motility by 60–100%. Among their partners, the number of pregnancies also increased