Contraceptive Injection: What the Birth Control Shot Really Does

The contraceptive injection — often called the birth control shot or Depo-Provera — is a progestin-only shot you get from a clinic every few months. It’s a low-maintenance option: no daily pill to remember, no device to check, and it’s hard for a partner to notice. Many people pick it for convenience, but there are trade-offs to know before you start.

How it works and effectiveness

The shot releases a progestin that prevents ovulation, thickens cervical mucus, and thins the uterine lining. With perfect use it’s nearly 99% effective; typical use puts it around the mid-90s percent. You get the injection every 12–13 weeks (about three months). If you stick to the schedule, it’s one of the most reliable non-permanent options.

What to expect and practical tips

Side effects vary. Some people have irregular bleeding or spotting for a few months, then lighter periods or no periods at all. Others report weight changes, mood shifts, acne, or headaches. Long-term use can reduce bone mineral density; this often reverses after stopping, but if you plan to use the shot for years, talk to your provider about monitoring bone health and calcium/vitamin D.

Fertility doesn’t come back immediately after the last shot. Many people need several months to get pregnant; for some it can take up to a year. If you may want a baby soon, consider a method that’s easier to stop, like an IUD or barrier methods.

Start-up timing matters. If you get the shot during the first five days of your period, you’re protected right away. If you start later, use backup contraception (condoms) for 7 days. If you miss the 12–13 week window, call your clinic — you may need a pregnancy test or short-term backup protection.

The shot doesn’t protect against STIs. Use condoms to reduce STI risk. It’s usually safe for breastfeeding people, but check with a provider if you’re nursing newborns.

Where to get it: family planning clinics, community health centers, some primary care offices, and Planned Parenthood. The injection must be given by a trained clinician — pharmacies generally won’t administer it unless they have a clinic attached.

Before you choose the shot, discuss your health history with a clinician. The shot isn’t recommended if you are pregnant or have certain cancers or unexplained vaginal bleeding. Ask about interactions if you take other meds — most drugs don’t change the shot’s effect, but it’s smart to double-check.

Quick checklist: set reminders for the three-month shot, plan if you want children soon, watch for menstrual changes, and keep in touch with your clinic for follow-up. If you want a low-fuss, highly effective option and understand the side effects, the contraceptive injection can be a solid choice.