Contraceptive injection

What is it?

The contraceptive injection contains the hormone progestogen. There are two types of injection:

• Depo-Provera provides contraception for three months (12 weeks)
• Noristerat provides contraception for two months (eight weeks)

Depo-Provera is the most used injectable method in the UK. Injectable contraception is a long-acting method of contraception.

How does it work?

The main way it works is by stopping the ovaries releasing an egg (ovulation) each month. It also:

• Thickens the mucus in the cervix, making it difficult for sperm to reach an egg
• Makes the lining of the womb thinner so it's less likely to accept a fertilised egg

Myths about the contraceptive injection:

• It makes you infertile. Not true - but normal fertility can take up to a year to return after using Depo-Provera
• You can only use it for two years. Not true - it can be used for longer providing you do not have any risk factors for osteoporosis (being over 45, poor diet, low exercise or family history of osteoporosis)

How reliable is it?

It's more than 99 per cent effective. This means that using this method, fewer than one woman in 100 will get pregnant in a year. All long-acting reversible methods are very effective because while they're being used you don't have to remember to take or use contraception.

How to use the contraceptive injection

The hormone is injected into a muscle, usually in your bottom. Depo-Provera can also sometimes be given in the leg or arm. The injection can be started up to and including the fifth day of your period. If started at any other time, additional contraception has to be used for seven days.

Advantages and disadvantages

The advantages of the contraceptive injection include:

• It's very effective
• It doesn’t interrupt sex
• You can use it if you can't use oestrogens or are breastfeeding
• It may reduce heavy painful periods and help with premenstrual symptoms for some women
• It may give you some protection against cancer of the womb
• It may give you some protection against pelvic inflammatory disease
• It isn't affected by other medicines

The disadvantages include:

• Your periods may change in a way that is not acceptable to you, or they may stop
• Irregular bleeding may continue for some months after you stop the injection
• You may put on weight when you use Depo-Provera
• Some women report having headaches, acne, mood changes and breast tenderness
• The injection lasts for eight or 12 weeks, so if you have side effects they will continue during this time and for some time afterwards
• Your periods and normal fertility may take some time to return - more than a year for some women
• The evidence about the risk of breast cancer in women using hormonal contraception is contradictory, but research suggests that women who use hormonal contraception may have a slightly increased risk of being diagnosed compared to women who don’t use it

Other things you may want to consider include:

• Once you've had the injection you don't need to think about it until it needs replacing
• You don't need a cervical screening test or internal examination to have the injection
• It doesn't protect you against sexually transmitted infections
• Depo-Provera affects your normal oestrogen level, which may cause thinning of the bones, but once you stop, any risk is reversed - women aged under 18 and over 45 will be carefully counselled about this

Can anyone use it?

Most women can have the contraception injection, but it may be unsuitable if you:

• Think you might already be pregnant
• Want a baby within the next year
• Don't want your periods to change
• Have thrombosis, heart or circulatory disease
• Have active liver disease
• Have breast cancer now or within the past five years
• Have migraines with aura
• Have diabetes with complications or have had diabetes for more than 20 years
• Have risk factors for osteoporosis

Where can I get it?

Injectable contraception is free on the NHS from contraception clinics, sexual health clinics and general practice.

Advice and support

Call the FPA helpline on 0845 122 8690.