The normal testosterone level for the average adult male is 270 to 1,070 nanograms per deciliter of blood, according to Healthline. This normal range may change depending on the male's age.
Healthline states that testosterone levels increase in men during puberty. Before puberty, the average testosterone level of a 10-to-11-year-old boy is between 7 and 130 nanograms per deciliter of blood. Once the boy reaches 17 to 18 years old, the normal testosterone range is 300 to 1,200 nanograms per deciliter of blood. Testosterone increases after puberty because it allows the boy to become more masculine in appearance. After a man turns 30, his testosterone levels decrease by 1 percent each year.