Contraceptive injections

Effectiveness: The injection is most effective when used perfectly. It's 99% effective at preventing pregnancy with perfect use and 94% effective with typical use.

Fit and forget: Once you've had an injection, you don't need to remember to take or use contraception for 3 months (except Noristerat users – you’ll need another injection after 8 weeks). But remember to have your next injection on time.

Periods: Periods are likely to change. They may stop completely, or bleeding may be lighter, irregular, heavier or last longer.

STI protection: No. Use external condoms or internal condoms to help protect yourself from STIs.

Hormones: Contains one hormone – progestogen.

If 100 sexually active women don’t use any contraception, 80 to 90 will get pregnant in a year.

If the injection is always used perfectly, according to instructions, it’s over 99% effective. This means that fewer than one in 100 injection user will get pregnant in a year.

If the injection is not always used according to instructions, about 6 in 100 injection users will get pregnant in one year.

It’s important to have your next injection at the right time. If you miss, or are late, having the next injection you may not be protected from pregnancy.

The injection is a method of long-acting reversible contraception (LARC). LARC is very effective because while it’s being used you don’t have to remember to take or use contraception.

Can anything make a contraceptive injection less effective?

While the injection is working, nothing will make it less effective.

The contraceptive injection isn't affected by:

• prescribed medicines, including antibiotics
• any medicines which you buy over the counter at a pharmacy
• diarrhoea
• vomiting.

It’s important to have your next injection at the right time – every 13 weeks for Depo-Provera and Sayana Press or every eight weeks for Noristerat.

If you miss or are late having your next injection it may mean that you’re no longer protected against pregnancy.

The contraceptive injection can be used by most people. Your doctor or nurse will need to ask you about your own and your family’s medical history to make sure a contraceptive injection is suitable. Do mention any illness or operations you’ve had. 

You may be advised not to use the injection if you:

• think you might already be pregnant
• don't want your periods to change
• want a baby within the next year
• have breast cancer
• have unexplained vaginal bleeding (for example, bleeding between periods or after sex)
• have arterial disease or history of serious heart disease or stroke
• have severe disease of the liver
• have risk factors for osteoporosis (thinning of the bones) See below, Contraceptive injections and your bones.

How long can I use a contraceptive injection for?

You can continue to use the injection until you’re 50 years old, as long as there are no medical reasons not to and you’re not at risk of osteoporosis (see below, Contraceptive injections and your bones).

If you use the injection for a long time, you should expect to have your risk factors for osteoporosis re-assessed every two years.

The doctor or nurse may ask you about your lifestyle and discuss whether it’d be more suitable for you to use a different method of contraception.

• You don’t have to think about contraception for as long as the injection lasts.
• It’s not affected by other medicines.
• It may reduce heavy painful periods and help with premenstrual symptoms for some people.
• You can use it if you’re breastfeeding.
• It’s a good method if you can’t use estrogens, like those in the combined pill, contraceptive patch and contraceptive vaginal ring.

• Your periods may change in a way that’s not acceptable to you (see below, Periods and fertility).
• Irregular bleeding may continue for some months after you stop the injections. 
• Some people may put on weight when they use Depo-Provera or Sayana Press (see Will my weight be affected by a contraceptive injection? in the Other things to know section). 
• The injection works for 13 or eight weeks, depending on which type you have. It can’t be removed from your body, so if you have any side effects, you have to be prepared for them to continue during this time and for some time afterwards.
• There can be a delay of up to one year before the return of your periods and fertility after stopping the injection.
• Contraceptive injections don’t protect you from sexually transmitted infections, so you may have to use condoms as well. 
• Some people experience side effects such as spotty skin, hair loss, decreased libido, mood swings and headaches.

• Using Depo-Provera or Sayana Press may affect your bones (see below, Contraceptive injections and your bones.)
• Research on the risk of breast cancer and injectable contraception use is complicated and hasn't given definitive answers. People who are currently using the injection may have a small increased risk of breast cancer compared to those who don’t use currently use the injection. Any increased risk is likely to be small and reduce with time after stopping the injection. 
• You can have an allergic reaction to the injection, but this is rare.
• As with any injection, there’s a small risk of a reaction at the spot the injection is given, which may cause irritation, swelling or a scar.

Your doctor or nurse should discuss all risks and benefits with you.

The main way they work is to stop your ovaries releasing an egg each month (ovulation). They also:

• thicken the mucus from your cervix (entrance to the womb), making it difficult for sperm to move through it and reach an egg
• make the lining of your uterus (womb) thinner to stop a fertilised egg implanting.

Will a contraceptive injection affect my periods?

Your periods will probably change.

• Most often, periods will stop completely.
• Some injection users will have irregular bleeding or spotting (bleeding between your usual bleeds).
• Some injection users will have bleeding that lasts longer and is heavier.

These changes may be a nuisance but they’re not harmful.

If you do have prolonged bleeding, it may be possible for the doctor or nurse to give you some additional hormone or medicine that can help control the bleeding. They may also check that the bleeding isn't due to other causes, such as an infection.

What should I do if I think that I'm pregnant?

Contraceptive injections are highly effective. If you’ve had your injection on time, it’s very unlikely you’ll get pregnant. If you think that you might be pregnant then do a pregnancy test or speak to your doctor or nurse as soon as possible. Using the contraceptive injection doesn’t affect a pregnancy test. If you do get pregnant while you’re using the injection, there’s no evidence that it’ll harm the baby.

What should I do if I want to stop using a contraceptive injection or try to get pregnant?

If you want to stop a contraceptive injection, all you need to do is not have your next injection.

Your periods and fertility may take a while to return to normal after you stop using the injection. However, it’s possible to get pregnant before your first period after stopping the injection. If you don’t wish to get pregnant then you should use another method of contraception from the day that your injection would’ve been due. If you have sex without using another method of contraception you may want to consider using emergency contraception.

If you want to try for a baby, start pre-pregnancy care such as taking folic acid and stopping smoking. You can ask your doctor or nurse for further advice.

I've just had a baby. Can I use a contraceptive injection?

The injection can be started any time after giving birth. If you start the injection before three weeks (21 days) you’ll be protected against pregnancy immediately. If it’s started later than day 21, you’ll need to use an additional method of contraception, such as condoms, or avoid sex for the first seven days.

When using the injection within six weeks of giving birth, you may be more likely to have heavy and irregular bleeding.

The injection can be used safely if you’re breastfeeding.

Can I use a contraceptive injection after a miscarriage or abortion?

The injection can be started immediately after an abortion or miscarriage and you’ll be protected against pregnancy straight away.

If you start the injection more than five days after a miscarriage or abortion then follow the advice in When can I start using a contraceptive injection? in the Other things to know section.

You can get the injection from a contraception or sexual health clinic or a doctor or nurse at a general practice.

All treatment is free and confidential.

How does a contraceptive injection affect my bones?

• Using Depo-Provera or Sayana Press affects your natural estrogen levels, and may cause thinning of the bones. This isn’t normally a problem for most injection users as the bone replaces itself when you stop the injection and it doesn’t appear to cause any long-term problems.
• Thinning of the bones may be more of a problem if you already have risk factors for osteoporosis (see below, Can I use a contraceptive injection if I’m at risk of osteoporosis?). 
• If you’re under 18 years old you may use Depo-Provera or Sayana Press, but only after careful evaluation by a doctor or nurse. This is because young people under 18 are still making bone.

Can I use a contraceptive injection if I'm at risk of osteoporosis?

If you have risk factors for osteoporosis (thinning of the bones) it’s normally advisable to use another method of contraception. Your doctor or nurse will talk to you about this. Risk factors include:

• being underweight
• smoking
• heavy drinking
• long-term use of steroids
• a close family history of osteoporosis
• certain medical conditions affecting the thyroid and digestive system.

You can help to make your bones healthier by doing regular weight-bearing exercise such as running and walking, eating a healthy diet with enough calcium and vitamin D, cutting down on drinking alcohol, and stopping smoking.

The Royal Osteoporosis Society website can give you more information.

Should I have my bones scanned before I start a contraceptive injection?

A bone scan before starting a contraceptive injection isn’t usually recommended. It may be useful for some people – usually those who’ve been identified as having risk factors for osteoporosis.

Will I be able to choose which contraceptive injection I use?

You’ll usually be offered Depo-Provera or Sayana Press. Your doctor or nurse can discuss with you which contraceptive injection is the most suitable for you.

How is a contraceptive injection given?

For Depo-Provera or Sayana Press, you’ll need to have an injection once every 13 weeks.  

Depo-Provera is injected into a muscle, usually in your buttocks. It can also sometimes be given in the arm. 

Sayana Press is injected just beneath the skin at the front of the thigh or abdomen, with a tiny needle. It’s possible for you to be taught how to inject Sayana Press yourself at home but not all clinics and general practices currently offer this option. you should have a responsible adult with you when you inject Sayana Press in case you have a reaction to it (this is very unlikely). 

Noristerat (which is given every eight weeks, injected into a muscle) isn't commonly used in the UK.

You don’t need to have a vaginal examination or a cervical screening test to have a contraceptive injection.

Will my weight be affected by a contraceptive injection?

Depo-Provera and Sayana Press are associated with an increase in weight in some people. If you’re under 18 years old and overweight before starting Depo-Provera or Sayana Press you may be more likely to gain weight with use.

When can I start using a contraceptive injection?

You can start a contraceptive injection any time in your menstrual cycle if it’s certain that you’re not pregnant.

If you start the injection during the first five days of your period you’ll be protected against pregnancy immediately.

If you start it on any other day, you won’t be protected for the first seven days. You’ll need to use additional contraception, such as condoms, or avoid sex, during this time.

If I have to go into hospital for an operation should I stop using a contraceptive injection?

No. It’s not necessary to stop a contraceptive injection if you’re having an operation. However, it’s always recommended that you tell the doctor that you’re using a contraceptive injection.

How often do I need to see a doctor or nurse?

You only need to go to the clinic or your general practice when your injection is due. If you have any problems or want to ask any questions between injections, contact your doctor or nurse.

If you’ve been given a supply of Sayana Press to inject at home, you’ll need to see a doctor or nurse at least once a year.