Birth Control Shot: 7 Facts an Ob/Gyn Wants You to Know
This injection protects against pregnancy for 3 months at a time.

While the Pill still remains one of the most common birth control methods, more and more people are turning to easier options—that is, birth control methods that last longer and are more effective at preventing pregnancy.
One such method is the shot, also known by the brand name Depo-Provera. “The birth control shot is an injection of the hormone progestin that protects against pregnancy for three months at a time,” says Kecia Gaither, MD, director of perinatal services at Lincoln Medical and Mental Health Center.
Looking for a new birth control option? Here’s what you need to know before starting the shot:
1. You only need to think about it every three months.
Unlike the Pill, you don’t have to think about the shot every single day. You only need to make sure you visit the doctor every three months to receive the shot, which goes in your upper arm or butt. Some health centers may also provide the shot for you to take home and give to yourself.
2. The shot works like other progestin-only birth control methods.
Like the birth control implant and the hormonal IUD, the shot contains only progestin—as opposed to a combination of progestin and estrogen found in other forms of birth control. “Progestin thickens cervical mucus, and makes it harder for sperm to enter the uterus and fertilize the egg,” says Dr. Gaither.
Additionally, progestin thins the lining of the uterus, which prevents the egg from attaching to the uterine wall. Some people on the shot or other progestin-only birth control options may not ovulate at all—meaning no egg is released.
3. The shot is 94 percent effective at preventing pregnancy.
This statistic takes into account human error—such as not getting the shot on time after three months. When the shot is used correctly, it’s actually 99 percent effective, according to Dr. Gaither.
“If you’re more than two weeks late for an injection, you may need to get a pregnancy test before the shot to play it safe,” says Dr. Gaither.
Keep in mind that the shot only protects against pregnancy. It is not meant to protect against sexually transmitted diseases, so you may still want to use condoms to protect against STDs.
4. Don’t use the shot if you want to get pregnant right away after you stop.
Some birth control methods allow pregnancy immediately after discontinuing use. For example, after taking out an IUD, you can essentially get pregnant right away.
The shot is different, at least for some women. “It is possible to get pregnant as soon as 12 weeks following the last injection,” says Dr. Gaither. “Though for some, it can take nine months or longer for fertility to return.”
5. The shot may affect your period.
Many types of hormonal birth control can alter your period, and the shot is no different. It varies from person to person, but you may notice one or more of the following changes after starting the shot:
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Irregular bleeding
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Lighter periods
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No periods at all
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And fewer menstrual cramps.
In fact, some people specifically use the shot and other hormonal birth control methods specifically to ease severe menstrual cramps or heavy, painful periods.
6. The shot may affect bone health.
“Studies have found that the shot decreases bone mineral density while you use it, so women shouldn’t use it for more than two years,” says Dr. Gaither. At that point, it might be wise to switch to a different birth control method.
Either way, it’s a good idea for all women to adopt habits that reduce their risk of osteoporosis. This includes making sure your diet includes enough calcium and vitamin D, and doing plenty of weight-bearing exercises to keep bones strong.
7. The shot may affect weight.
The majority of people who try the shot for birth control do not notice any changes to their weight. One study, however, did show that about a quarter of the women gained 5 percent of their starting weight within the first six months.
“If you’re someone who’s concerned about gaining weight, talk to your doctor about the best birth control option for you,” says Dr. Gaither.
Dr. Gaither, an ob-gyn and maternal fetal medicine specialist, is director of perinatal services at Lincoln Medical and Mental Health Center, a member of NYC Health + Hospitals System in Bronx, New York.
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[MUSIC]
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The birth control shot is an injection
of the hormone progestin,
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that protects against pregnancy for
three months at a time.
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You get it in your upper arm or butt.
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The shot doesn't protect against
sexually transmitted diseases.
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Here's what else I tell my patients about
using the shot for birth control control.
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[MUSIC]
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You don't really need to
think about the shot,
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other than going to the doctor
every three months.
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The shot works similarly to other
progestin-only birth control options
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like the implant and hormonal IUDs.
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Progestin thickens cervical mucus and
makes it harder for
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sperm to enter the uterus and
fertilize the egg.
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It thins the lining of the uterus,
which makes it harder for
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a fertilized egg to attach.
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And may even prevent you from
ovulating in the first place.
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The shot is 94% effective
at preventing pregnancy.
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Now, this number jumps to
99% with perfect use, but
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some women forget to get
their shots on time.
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If you're more than two weeks late for
an injection,
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you may need to get a pregnancy test
before the shot, to play it safe.
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Don't use the shot if you wanna get
pregnant right away once you stop.
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It is possible to get pregnant as soon as
12 weeks following the last injection,
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though for some, it can take 9 months or
longer for fertility to return.
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The shot may affect your period.
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You may get irregular or some frequent
bleeding between the first few shots.
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Many women on the birth control shot have
lighter periods or no periods at all and
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fewer menstrual cramps.
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The shot can affect your bone health.
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Studies have found that the shot decreases
bone mineral density while you use it,
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so women shouldn't use it for
more than two years.
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It's a good idea to reduce other
risk factors for osteoporosis,
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by getting enough calcium and vitamin D
and plenty of weight-bearing exercise.
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Some women complain about weight gain.
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One study found that about 25% of women
gained about 5% or more of their starting
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weight within the first six months, but
some women don't gain weight on the shot.
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If you're someone who's
concerned about gaining weight,
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talk to your doctor about the best
birth control option for you.
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So let's recap.
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The shot is 94% effective
at preventing pregnancy.
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You get it every three months.
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You need a prescription and
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the shot doesn't protect you from
sexually transmitted diseases.
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[MUSIC]
Birth control shot. New York, NY. Planned Parenthood. (Accessed on October 17, 2021 at https://www.plannedparenthood.org/learn/birth-control/birth-control-shot.)
Depot medroxyprogesterone acetate (DMPA) for contraception: formulations, patient selection and drug administration. Waltham, MA: UpToDate, 2021. (Accessed on October 17 ,2021 at https://www.uptodate.com/contents/depot-medroxyprogesterone-acetate-dmpa-for-contraception-formulations-patient-selection-and-drug-administration.)
Hormonal contraception for suppression of menstruation. Waltham, MA: UpToDate, 2021. (Accessed on October 17, 2021 at https://www.uptodate.com/contents/hormonal-contraception-for-suppression-of-menstruation.)