The contraceptive injection is a form of contraception that uses a synthetic form of progesterone to prevent pregnancy. Different contraceptive injection types last for different periods of time, but as a general rule, this contraceptive method protects against pregnancy for between 8 and 13 weeks.
Contraceptive injections do not protect against sexually transmitted infections (STIs). For this kind of protection, you’ll need to use an alternative form of contraception such as female condoms.
How the contraceptive injection works
The contraceptive injection works by releasing progestogen, a synthetic version of the hormone progesterone, into the bloodstream. This helps to prevent pregnancy by reducing the likelihood of ovulation, making the cervical mucus thicker to block sperm from entering the womb and thinning the lining of the womb to make it less likely for fertilised eggs to implant.
Depending on which type of contraceptive injection you have, it will be injected into the bottom, arm or tummy. Some contraceptive injections can be self-administered once you have been taught how to do it by a nurse or doctor.
Starting the contraceptive injection
As long as you’re not pregnant, you can have the contraceptive injection at any time during your menstrual cycle. Having the injection within the first 5 days of your menstrual cycle will provide you with protection against pregnancy from the start. If you have the injection after day 5, you’ll need to use alternative contraception, such as condoms, for the following 7 days.
If you’re breastfeeding, you usually won’t be given the injection until 6 weeks after the baby’s birth. If not, you can have the injection at any time after childbirth. If you have the injection within the first 21 days after childbirth, you’ll be protected against pregnancy straight away. If not, you’ll need to use an additional form of contraception for the first 7 days of use.
For those who have recently had a miscarriage or an abortion, the contraceptive injection can be given immediately. You’ll be protected against pregnancy from the first injection if you have it within 5 days of your abortion or miscarriage. If more than 5 days have passed, an alternative form of contraception, such as condoms, will be needed for the next 7 days.
What to do if you forget to have the contraceptive injection
If you forget to renew your contraceptive injection and have unprotected sex, you may need to use emergency contraception to avoid pregnancy. It is important to remember that the contraceptive injection offers no protection against STIs, so it may be wise to get tested at a sexual health clinic if you think you’re at risk.
The contraceptive injection is not suitable for pregnant women. Even if you have used emergency contraception, it’s best to be sure you’re not pregnant before you start having the injection again. Taking a pregnancy test three weeks after you last had unprotected sex can help you to find out. In the meantime, you should use an alternative method of contraception.
Who can have the contraceptive injection?
The majority of women can have the contraceptive injection. However, it isn’t suitable for everyone. The injection might not be right for you if:
- You have or have had breast cancer
- You’re at risk of osteoporosis
- You’ve experienced unexplained bleeding after sex or between periods
- You have liver disease or arterial disease
- You have a history of strokes or heart disease
- You don’t want your periods to change
- You plan to have a baby in the next year
- You think you may be pregnant
The contraceptive injection is suitable for women who cannot take oestrogen-based contraceptives, as well as those who struggle with remembering to take daily or weekly contraceptives. It can also be used while breastfeeding.
How effective is the contraceptive injection?
The contraceptive injection is believed to be 99% effective at preventing pregnancy. Contraceptive injection effectiveness is thought to be rarely impacted by taking other medicines or having certain medical conditions - your pharmacist can advise you if you’re unsure about this.
Common side effects of the contraceptive injection
Contraceptive injection side effects can range from altered periods, to temporarily reduced fertility, to symptoms including headaches and nausea. These side effects can be short-term, but they may last longer than the duration of the injection’s effectiveness.
A change in fertility is one such side effect. The contraceptive injection reduces your fertility to lower the risk of pregnancy, but your fertility may not return to its normal level until 1 year after you stop using it. For this reason, it is advised that you don’t choose this method of contraception if you are planning to have a baby in the near future.
The contraceptive injection can have some positive side effects, such as reducing period pain and causing lighter periods. However, it can also have the undesirable effects, and may also cause weight gain, hair loss, headaches, acne, lowered sex drive and mood swings.
Risks of having the contraceptive injection
The contraceptive injection carries a minor risk of infection at the area where it is administered. There is also a chance that you may be allergic to the injection, so it is important to notify your medical team of any allergies or sensitivities you have when discussing which is the best contraception for you.
Additionally, some contraceptive injections may cause a thinning of the bones. This is why it isn’t recommended for those at risk of osteoporosis. This isn’t usually dangerous, though - speak to your pharmacist if you’re concerned about the risks.
Where to get the contraceptive injection
The contraceptive injection is available for free to all users from places such as:
- Genitourinary medicine (GUM) or sexual health clinics
- Some GP surgeries
- Contraception clinics
- Some young people’s services
Some types of contraceptive injection aren’t available in all clinics. If you have a specific preference, it’s best to check ahead of time if your chosen clinic provides the service. The clinic staff will be able to advise you on how different types of injections vary to help you come to an informed decision. For certain types of contraceptive injection, they will also be able to show you how to inject it yourself.