The contraceptive injection contains the hormone progesterone. This hormone works to thicken the mucus in the cervix, stopping sperm from reaching an egg. It also thins the lining of the womb and, in some, prevents the release of an egg.
Who can use the contraception injection?
Most women can be given the contraceptive injection. It may not be suitable if you:
- think you might be pregnant
- want to keep having regular periods
- have bleeding in between periods or after sex
- have arterial disease or a history of heart disease or stroke
- have a blood clot in a blood vessel (thrombosis)
- have liver disease
- have migraines
- have breast cancer or have had it in the past
- have diabetes with complications
- have cirrhosis or liver tumours
- are at risk of osteoporosis
After having a baby
You can have the contraceptive injection at any time after you have given birth, if you are not breastfeeding. If you are breastfeeding, the injection will usually be given after six weeks, although it may be given earlier if necessary.
After a miscarriage or abortion
You can have the injection immediately after a miscarriage or abortion, and you will be protected against pregnancy straight away.
Know the facts
- The injection is over 99% effective
- One injection can protect you from pregnancy for 8, 12 or 13 weeks depending on the type you are using
- The injection is a long acting reversible method of contraception (LARC)
- It doesn’t protect you from sexually transmitted infections (STIs) so you will need to use condoms as well
Advantages & Disadvantages
The Advantages
- The injection is not affected by other medicines
- It does not interrupt sex
- The injection is an option if you cannot take oestrogen based contraception
- It may reduce painful periods
The Disadvantages
- Periods may be irregular or stop altogether
- It can cause slight thinning of the bones by reducing bone mineral density (this usually recovers once the injections stop)
- It may take a while for your periods to return to normal when you stop having the injection
- It can cause some side effects including headaches, mood swings, breast tenderness and irregular bleeding.
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