The contraceptive injection protects you against pregnancy for eight weeks or 12 weeks, depending on the type you use.
What is it?
An injection given every few weeks. There are two versions available: Depo-Provera, which lasts for 12 weeks, and Noristerat, which lasts for eight weeks. The most popular is Depo-Provera.
How does it work?
The injection contains progestogen (a synthetic version of the natural hormone progesterone). Progestogen thickens the mucous in the cervix, which stops sperm reaching an egg. It also thins the lining of the womb so that an egg can't implant there. In some women it also stops ovulation (the release of an egg).
How effective is it?
If used correctly it is over 99% effective. This means that less than one woman in 100 who use the injection will become pregnant in a year.
The injection can be useful for women who might forget to take the Pill every day. It may provide some protection against cancer of the womb and pelvic inflammatory disease.
Anything else to know about?
Side effects can include:
- Weight gain.
- Mood swings.
- Breast tenderness.
If you do experience side effects, you’ll have to put up with them for as long as the injection lasts (the full eight or 12 weeks). Your periods may also become more irregular or longer, or stop altogether.
It can also take up to a year for your fertility level to get back to normal afterwards, so it may not be suitable if you want to have a baby in the near future.
Using Depo-Provera affects your natural oestrogen levels, causing thinning of the bones. This is not normally a problem for most women as the bone replaces itself when you stop the injection and it does not appear to cause any long-term problems.
A doctor will be able to advise you if you are suitable for the injection due to possible medical conditions. They will fully assess you and give you advice or alternative suggestion for contraception. This will be free and confidential.
If you aren't in a monogamous (faithful) relationship you should help protect yourself against sexually transmitted infections by using condoms as well as the injection.