To help prevent pregnancy, a person can get a birth control shot. However, it can cause side effects, so it is important to consider these before choosing this form of birth control.

In this article, we look at how the birth control shot works, how effective it is, and how to get it.

A doctor cleans a patient's arm after administering a birth control shot (Depo-Provera).Share on Pinterest
A person needs a Depo-Provera shot every 3 months to ensure it remains effective in preventing pregnancy.

The birth control shot, or depo shot, Depo-Provera, or DMPA, is an injection that a person can get once every 3 months to prevent pregnancy.

The Depo-Provera shot is temporary, which means that if a person wants to become pregnant, they can do so after they stop using it.

According to Planned Parenthood, a person must have a birth control shot every 3 months, or approximately every 12–13 weeks. This amounts to 4 times a year.

When a person uses the birth control shot perfectly, it is 99% effective. However, not everybody uses birth control correctly. Sometimes people forget to renew their birth control shot or are unable to get an appointment in time.

This lowers the birth control shot’s efficacy. Planned Parenthood indicate that, in reality, the birth control shot is about 94% effective. According to the Centers for Disease Control and Prevention (CDC), 6 out of every 100 people using the birth control shot may become pregnant in the first year of using Depo-Provera.

According to the U.S. Department of Health & Human Services (HHS), the birth control shot contains a hormone called progestin, which can prevent ovulation.

Ovulation is the process in which the ovaries release eggs for fertilization by sperm in the womb. If no eggs leaving the ovaries, pregnancy cannot occur.

The birth control shot also thickens the mucus in the cervix by releasing progestogen. This means that sperm cannot penetrate the cervix to fertilize an egg.

In a study cited by the CDC, researchers found that cervical mucus was not suitable for penetration by sperm 24 hours after the first birth control shot. This was true for 90% of the people included in the study.

According to the American College of Obstetrics and Gynecology (ACOG), progestin thins the uterus lining. A 2016 study indicates that pregnancy can occur when the endometrial lining is 4–5 millimeters (mm) thick. However, a woman is less likely to get pregnant if the lining is less than 6mm thick.

According to the CDC, the time at which a person gets their birth control shot can vary depending on the circumstances:

First time

A person can get their first birth control shot whenever they want to, providing that they are not pregnant.

However, if a person gets the shot later than 7 days after their period started, they should either abstain from having sex or use additional contraceptives, such as condoms, for the next week.

Early injection

A person can get an early birth control shot when it is necessary.

Late Injection

A person can get the shot 2 weeks late, or 15 weeks from the previous injection, without needing to use additional contraception.

However, if a person has unprotected penetrative sex more than 15 weeks after their last birth control shot, they can have the injection providing that they are reasonably sure they are not pregnant.

They must use other forms of contraception, such as condoms, for 7 days after the shot as the injection will not protect against pregnancy during this time.

As with any type of contraception, the birth control shot has several advantages and disadvantages that a person should consider.


  • The birth control shot does not interrupt sex.
  • A person does not have to remember to take an oral birth control pill every day.
  • A person may be able to self-administer the birth control shot at home.
  • A person does not need to have any medical tests or exams before having their first birth control shot.
  • The birth control shot can stop or reduce periods or make them lighter.
  • A person can become pregnant again once they have stopped using the birth control shot.
  • The birth control shot is safe to use immediately after giving birth or while breastfeeding.
  • People with sickle cell disease may experience reduced sickle crisis pain while using the birth control shot.


  • Depo-Provera does not protect against sexually transmitted diseases (STDs). A person should use other types of contraception, such as condoms to protect against STDs, including HIV.
  • A person needs to renew the birth control shot precisely every 13 weeks.
  • Delays in renewing the birth control shot can reduce its efficacy.
  • According to the Food and Drug Administration FDA, the median time to conceive after discontinued use, with no other form of birth control, is 10 months; however, it may take 18 months.

As with other forms of birth control, side effects can occur, including:

  • weight gain
  • irregular bleeding
  • nausea
  • headaches
  • sore breasts
  • depression

According to Planned Parenthood, side effects typically disappear after 2–3 months.

The FDA warn that the birth control shot may also reduce bone mineral density and that this reduction may increase the longer the person uses the shot.

However, according to the ACOG, there appears to be no clinical evidence that the bone mineral density loss is clinically significant, and bone mineral density can recover after discontinued use.

According to Planned Parenthood, most people do not encounter problems when using this form of contraception. A person should see a doctor if they experience the following:

  • severe depression
  • very heavy bleeding
  • yellowing of the eyes and skin
  • migraine with aura

A healthcare provider will inject the shot into the muscles in the buttocks or the upper arm.

Where to get the birth control shot

A person typically has to get the shot from a doctor or nurse.

The cost of the birth control shot differs depending on a person’s location, the type of health insurance they have, or their eligibility for programs that will help them.

According to Planned Parenthood, a person can expect to pay up to $150 for the birth control shot.

A person may also need to pay between $0–$250 for the exam that they will need to undergo before having the first injection.

Most health insurance plans will cover FDA-approved birth control for women, according to the Office on Women’s Health.

They also advise that some family planning and sexual health clinics may offer certain contraceptives for free or a reduced cost.

A person can find their local clinics with this tool.

Packages can differ from state to state. A person should check whether their Medicaid package covers the birth control shot in their state.

There is a minimal chance of infection at the injection site. If a person experiences pain, bleeding, or pus coming from the injection site, they should seek medical advice.

There may be a risk of pregnancy in some cases if a person wishes to switch from using a different type of birth control.

For instance, if someone wants to switch to the birth control shot from an intrauterine device (IUD), they may need to use the birth control shot alongside other contraceptives.

According to the CDC, if a person has had sex since the start of their period, and it has been over 5 days since bleeding began, there may still be sperm present that could fertilize an egg if ovulation occurs. To combat this, the IUD should remain in place for at least 7 days after choosing to have the birth control shot.

The Depo-Provera shot is not suitable for everyone.

People who should not use the birth control shot include those :

  • who are pregnant
  • who have unexplained vaginal bleeding
  • who have or have experienced breast cancer
  • with severe hypertension or vascular disease
  • with certain types of liver disease

The birth control shot is a short-acting contraceptive that lasts for 3 months.

A person must renew the shot every 3 months to ensure effectiveness.

With a potential failure rate of roughly 6%, it is not as effective as some other forms of birth control, but a significant number of people use it successfully.

As with other birth control methods, the shot works by releasing progestogen, which stops ovulation and blocks sperm.