The question here may be about what would happen if a man took birth control pills, but a more important question might be why a man would take birth control pills in the first place. Let's answer the what, and then take a brief look at the why.
But first, a bit of standard advice: Before taking any medication, consult a physician who can recommend the best course of treatment for you and your symptoms or condition.
Birth control pills contain two hormones, estrogen and progestin, that women's bodies produce naturally. When taken in the form of birth control pills, these hormones will regulate a woman's menstrual cycle and keep an egg from implanting in her uterus, thus keeping her from becoming pregnant. These hormones are also made in smaller amounts in men's bodies. Estrogen is used in sperm development, and progestin makes testosterone [source: Planned Parenthood].
If a man took just one or two birth control pills, nothing would happen. There is not enough of either hormone to throw a man's body out of balance with just a couple of pills. However, if a man took birth control pills regularly over an extended period, his breasts might grow slightly larger, his testicles might shrink a little, and his sex drive and amount of facial hair might decrease. He also might develop softer skin and wider hips [source: Guite]. Higher levels of estrogen also increase the risk of infertility, because an imbalance of the hormone affects production of quality sperm. Exhaustion, reduced muscle mass, osteoporosis, trouble focusing and even hot flashes are other known side effects of too much estrogen in a man [source: Healthline].
Now for just a bit about why a man may want to take them: Some may think that taking birth control pills can help a man become more feminine or transition. However, if the goal is to transition, there are safer and more effective ways to achieve the result, and the process should be overseen by a qualified medical professional at every turn. For example, a person who takes birth control pills to transition would be shocked to learn that the estrogen dose is only one-tenth the dose taken by transgender women. Also, it's a different type of estrogen altogether. The estrogen found in birth control pills can't be taken in ultra-high doses because even the normal amount comes with increased risk of deep vein thrombosis and heart attack [source: Guite].
So, if you're a man who took a pill or two, whether by accident or out of curiosity, don't fret. The side effects, if any, will be minimal. But if you're looking to transition, find an LGBTQ-friendly doctor to consult about the process. One way to do that is by checking the Gay and Lesbian Medical Association's database, or ask your personal doctor if they have experience in the area, or can make a referral [source: Burch]. Medicine has come a long way in this area in recent years, so there's no need to blindly find your way through!