What: One injection of progestin into the upper arm, administered in a doctor's office, is effective at preventing pregnancy for three months.
Failure rate*: 0.2–6%
Who: Women who can never remember to take their pill; women who don't plan to get pregnant in the near future.
- One quick pinch means women don't need to worry about pregnancy or periods for three months.
- No estrogen means no estrogen-related complications.
- It can be an effective treatment for pelvic pain caused by intense periods or endometriosis, says Carusi.
- It's not a reliable long-term plan because it can deplete calcium stored in the bones, and the manufacturer warns against using the shot for longer than two years. Carusi says that her office counsels teens, whose bones are still forming, and perimenopausal women, whose bones may be weakening, to consider other methods after a year or two.
- Some women don't do shots, period.
- Weight gain is common.
- If you happen to experience negative side effects, like hair loss, depression, or a change in sex drive, appetite or weight, you'll have to deal with them for 12 to 14 weeks until the shot wears off.
- It can take months to a year for a woman to become pregnant after stopping the medication, Carusi says.