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Contraceptive injections

Contraceptive injections contain a progestogen hormone which is similar to the natural progesterone that women produce in their ovaries. There are 2 types of injection. Depo-Provera protects you from pregnancy for 12 weeks and Noristerat protects you for 8 weeks. Both of these are very effective hormonal methods of contraception. Depo-Provera is the most commonly used in the UK.

How effective is a contraceptive injection?

How effective any contraceptive is depends on how old you are, how often you have sex and whether you follow the instructions.

If 100 sexually active women don’t use any contraception, 80 to 90 will become pregnant in a year. If used according to the instructions, injections are over 99% effective. This means that less than 1 woman in 100 will get pregnant in a year.

How do contraceptive injections work?

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

  • Thicken the mucus from your cervix. This makes it difficult for sperm to move through it and reach an egg

  • Make the lining of your womb thinner so it is less likely to accept a fertilised egg.

Where can I get the injection?

Only a doctor or nurse can give you the injection. You can go to a family planning clinic or to the doctor or nurse at your general practice. If you prefer not to go to your own general practice, or they don’t provide contraceptive services, they will give you information about another practice or clinic. All treatment is free and confidential (see How do I find out about contraception services?).

Can anyone use a contraceptive injection?

Most women who want to can have a contraceptive injection. Your doctor or nurse will need to ask you about your own and your family’s medical history to make sure the injection is suitable. Do mention any illness or operations you have had. Some of the conditions which may mean you should not use the injection are:

  • You think you might already be pregnant

  • You do not want your periods to change.

You have now or have had in the past:

  • Breast cancer

  • Unexplained vaginal bleeding (for example, bleeding between periods or after sex)

  • Thrombosis (blood clots) in any vein 

  • A  heart attack or stroke (serious arterial disease)

  • High blood pressure

  • Diabetes with complications or diabetes for more than 20 years

  • Active liver disease

  • Risk factors for osteoporosis (see Can I use the injection if I am at risk of osteoporosis?)


What are the advantages of the contraceptive injection?

  • You don’t have to think about contraception for as long as the injection lasts.

  • It doesn’t interrupt sex.

  • You can use it if you are breastfeeding.

  • Depo-Provera and Noristerat are not affected by other medicines.

  • 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 gives some protection against pelvic inflammatory disease.

  • It is a good method if you cannot use estrogens (hormones), like those in the combined pill.

What are the disadvantages of the contraceptive injection?

  • Your periods may change in a way that is not acceptable to you (see Will the injection affect my periods?)

  • Irregular bleeding may continue for some months after you stop the injections.

  • Women may put on weight when they use Depo-Provera (see Will my weight be affected by the injection?).

  • Other possible side-effects include headaches, abdominal pain or discomfort, dizziness, spotty skin, tender breasts, bloating, and changes in mood and sex drive.

  • The injection works for 12 or 8 weeks, depending on which type you have. It cannot 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.

  • Your periods, and fertility, may take a few months to return after stopping Depo-Provera injections. Sometimes it can take more than a year for your periods and fertility to get back to normal.

  • Contraceptive injections do not protect you against sexually transmitted infections, so you may have to use condoms as well.

Are there any risks?

  • Using Depo-Provera may affect your bones (see How does Depo-Provera affect my bones?).
    Research about the risk of breast cancer and hormonal contraception is complex and contradictory.

  • Current research suggests that women who use hormonal contraception appear to have a small increase in risk of being diagnosed with breast cancer compared to women who don’t use hormonal contraception. Further research is ongoing.

  • You can have an allergic reaction to the injection, but this is very rare.

  • As with any injection there is a risk of a small infection at the site of the injection.

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

How does Depo-Provera affect my bones?

  • Using Depo-Provera affects your natural estrogen 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.

  • Thinning of the bones may be more of a problem for women who already have risk factors for osteoporosis (see Can I use the injection if I am at risk of osteoporosis?).

  • It is also a concern for young women under 19-years-old as the body is still making bone at this age. Although young women can use Depo-Provera, it is recommended that they should first consider all other suitable methods of contraception.

Will the injection affect my periods?

Your periods will probably change.

  • In some women periods will stop completely.

  • Some women will have irregular periods or spotting (bleeding between periods), especially to begin with.

  • Some women will have periods that last longer and are heavier.

These changes may be a nuisance but they are 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 is not due to other causes, such as an infection.

Will my weight be affected by the injection?

Not all women put on weight with the injection and some women lose weight. Some women using Depo-Provera for 1 to 2 years have reported putting on up to 8lbs (just under 4kg). Further weight gain may occur if Depo-Provera is used for longer periods of time.

When can I start using a contraceptive injection?

You will usually be given an injection during the first 5 days of your period. You will be immediately protected against becoming pregnant. If you have the injection on any other day you will not be protected for the first 7 days, so you will need to use another method of contraception, such as condoms, during this time.

When can I start the injection after having a baby, miscarriage or abortion?

The injection is usually given from 6 weeks after you have given birth. Waiting until then makes it less likely that you will have heavy and irregular bleeding. If you want to use the injection before 6 weeks it can be started 3 weeks (21 days) after you have given birth. If you start the injection before day 28 you will be protected from pregnancy immediately. If it is started later than day 28 you will need to use an additional method of contraception for 7 days.

The injection can be started immediately after an abortion or miscarriage if you were pregnant for less than 24 weeks. You will be protected against pregnancy immediately.

Can I use the injection if I am breastfeeding?

It is safe to use a contraceptive injection while you breastfeed. It will not affect your milk supply or harm the baby. 

How is the injection given?

The hormone is injected into a muscle, usually in your bottom. Depo-Provera can also sometimes be given in the leg or the arm. Noristerat is a thicker solution so you may find the injection is slightly more painful when it is given. If you want to carry on using this method of contraception, you will need to have injections every 12 weeks if you have Depo-Provera injections, or every 8 weeks if you have Noristerat. You do not need to have a vaginal examination or cervical smear to have the injection.

Can anything make the injection less effective?

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

Injectable contraception is not affected by:

  • Prescribed medicines, including antibiotics

  • Any medicines which you buy over the counter at a pharmacy in the UK

  • Diarrhoea

  • Vomiting

It is important to go back at the right time for your next injection – every 12 weeks for Depo-Provera or every 8 weeks for Noristerat. Missing the next injection may mean that you are no longer protected against pregnancy. To ensure that you remain protected against pregnancy you should not be more than 2 weeks late for your next injection.

Will I be able to choose which injection I use?

It is most likely that you will be offered the injection Depo-Provera as Noristerat is usually only used for short periods of time, for example, while waiting for a sterilisation operation or for vasectomy to become effective. Your doctor or nurse can discuss with you which injection is most suitable.

Can I use the injection if I am at risk of osteoporosis?

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

  • A  lack of estrogen due to early menopause (before 45 years)

  • A lack of estrogen due to missing periods for 6 months or more, as a result of over-exercising, extreme dieting or eating disorders

  • Smoking

  • Heavy drinking

  • Long-term use of steroids

  • A close family history of osteoporosis

  • Certain medical conditions affecting the liver, 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 adequate in calcium and vitamin D, and cutting down on drinking alcohol and smoking.

The National Osteoporosis Society’s website can give you more information about osteoporosis.

Should I have my bones scanned before I start the injection?

It is not recommended that all women have a bone scan before they start the injection. There may be some women for whom it is useful, but these are usually women who have been identified as having risk factors for osteoporosis.

What should I do if I think that I am pregnant?

The injection is a highly effective method of contraception. If you have had your injections on time, it is very unlikely that you will become pregnant. If you think that you might be pregnant then you can do a pregnancy test or speak to your doctor or nurse as soon as possible. If you do get pregnant while you are using the injection, it will not harm the baby.

How long can I use the injection for?

You can continue to use Depo-Provera until the menopause, provided there are no medical reasons not to use it and you are not at risk of osteoporosis. If you do use the injection long term 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 would be more suitable for you to use a different method of contraception.

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

If you want to stop the injection all you need to do is not have your next injection. Your periods and natural fertility may take a while to return after you stop using the injection. However, it is possible to get pregnant before you have seen your first period. If you don’t wish to become pregnant then you should use another method of contraception from the day that your injection would have been due. If you have sex without using another method of contraception you may want to consider using emergency contraception (see Emergency contraception).

If you want to try for a baby, it helps to wait for one natural period before trying to get pregnant. This means that the pregnancy can be dated more accurately and you can start pre-pregnancy care such as taking folic acid and stopping smoking. You can ask your doctor or nurse for further advice. Don’t worry if you do get pregnant sooner, it will not harm the baby.

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

No. It is not necessary to stop the injection if you are having an operation.  However, it is always recommended that you tell the doctor that you are using the 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 between injections, you should contact your doctor or nurse.

How do I find out about contraception services?

Contraception is free for women and men of all ages through the National Health Service.

  • You can find out about all clinics from sexual health direct, run by fpa on 0845 310 1334 or visit the website

  • You can get lists of general practices from libraries, primary care trusts or health boards and some advice centres and helplines.

  • You can get details of your nearest family planning or sexual health clinic from: local directories, health centre, hospital, midwife or health visitor, advice centre, NHS Direct on 0845 46 47 (NHS 24 in Scotland 0845 4 24 24 24), primary care trust or health board.

  • Young people can also phone Brook on 0800 0185 023 or Sexwise on 0800 28 29 30 for details of the nearest young people’s clinic.

Emergency contraception

If you have had sex without using contraception or think your method might have failed there are two emergency methods you can use.

  • The emergency hormonal pill – must be taken up to 3 days (72 hours) after sex. It is more effective, the earlier it is taken after sex.

  • An IUD – must be fitted up to 5 days after sex, or up to 5 days after the earliest time you could have released an egg (ovulation).

Ask your doctor or nurse about getting emergency pills in advance, just in case you need them.

Sexually transmitted infections

Most methods of contraception do not protect you from sexually transmitted infections.

Male and female condoms, when used correctly and consistently, can help protect against sexually transmitted infections. Diaphragms and caps may also protect against some sexually transmitted infections. If you can, avoid using condoms containing Nonoxinol 9 (spermicidally lubricated), as this does not protect against HIV and may even increase the risk of infection.

How fpa can help you

sexual health direct is a nationwide service run by fpa. It provides:

  • Confidential information and advice on contraception, sexually transmitted infections, planning a pregnancy, pregnancy choices and sexual wellbeing

  • Details of family planning clinics, sexual health clinics and other sexual health services

  • A wide range of leaflets on individual methods of contraception, common sexually transmitted infections, abortion and planning a pregnancy.

fpa helplines

helpline 0845 310 1334
9am to 6pm Monday to Friday

Northern Ireland
helpline 028 90 325 488 (Belfast) or
helpline 028 71 260 016 (Derry)
9am to 5pm Monday to Thursday, 9am to 4.30pm Friday

helpline 0141 576 5088
9am to 5pm Monday to Thursday, 9am to 4.30pm Friday

or visit fpa's website

A final word

This section of Surgery Door can only give you basic information about the contraceptive injection. The information is based on the evidence and medical opinion available at the time this leaflet was printed. Different people may give you different advice on certain points. All methods of contraception come with a Patient Information Leaflet which provides detailed information about the method.
Remember – contact your doctor, practice nurse or a family planning clinic if you are worried or unsure about anything.

Registered charity number 250187

Supported by the Department of Health.
© fpa

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