Many trans men, and other trans people, choose to go on a prescription of artificial testosterone. Human bodies, including those of cis people, naturally contain both some estrogen and some testosterone — these are the sex hormones traditionally classified as "female" and "male," respectively. Most women have a larger amount of estrogen in their systems, and it's the other way around for men.

By introducing more testosterone to his body, a hormone-taking trans man will shift his chemical balance towards the levels that are more common in men, and away from the levels that are more common in women.

The effects of testosterone prescribed for trans people can include:

The changes produced by T (the short form, of course, of testosterone) are often very dramatic, though the results vary by individual. Some people who take testosterone never do grow much facial hair; sometimes it takes a long while for the voice to change, and so on.

There are several ways to introduce T into the body: