Contraceptive injections: your guide

Contraceptive injections contain a progestogen hormone which is similar to the natural progesterone that women produce in their ovaries.

There are two types of injection. Depo-Provera protects you from pregnancy for 12 weeks and Noristerat protects you for eight weeks. Depo-Provera is the most commonly used contraceptive injection in the UK.

Read this information to find out:

• How effective is a contraceptive injection?
• How do contraceptive injections work?
• Where can I get a contraceptive injection?
• How is a contraceptive injection given?
• Can anyone use a contraceptive injection?
• What are the advantages of a contraceptive injection?
• What are the disadvantages of a contraceptive injection?
• Are there any risks?
• How does Depo-Provera affect my bones?
• Can I use a contraceptive injection if I am at risk of osteoporosis?
• Should I have my bones scanned before I start a contraceptive injection?
• Will a contraceptive injection affect my periods?
• Will my weight be affected by a contraceptive injection?
• When can I start using a contraceptive injection?
• I've just had a baby. Can I use a contraceptive injection?
• Can I use a contraceptive injection after a miscarriage or abortion?
• Can anything make a contraceptive injection less effective?
• Will I be able to choose which contraceptive injection I use?
• What should I do if I think that I am pregnant?
• How long can I use a contraceptive injection for?
• What should I do if I want to stop using a contraceptive injection or try to get pregnant?
• If I have to go into hospital for an operation should I stop using a contraceptive injection?
• How often do I need to see a doctor or nurse?

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.

Contraceptive injections are over 99 per cent effective. This means less than four women in every 1,000 will get pregnant over two years.

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

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 uterus (womb) thinner so it is less likely to accept a fertilised egg.

Where can I get a contraceptive injection?

Only a doctor or nurse can give you a contraceptive injection.

You can go to a contraception or sexual health clinic or to the doctor or nurse at a general practice. All treatment is free and confidential (see How to get help with your sexual health).

How is a contraceptive injection given?

The hormone is injected into a muscle, usually in your buttocks. Depo-Provera can also sometimes be given in 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 eight weeks if you have Noristerat.

You do not need to have a vaginal examination or a cervical screening test to have a contraceptive injection.

Can anyone use a contraceptive injection?

Most women 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 a contraceptive 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 want a baby within the next year.

You have now or had in the past:

• breast cancer or breast cancer within the last five years
• unexplained vaginal bleeding (for example, bleeding between periods or after sex)
• arterial disease or history of serious heart disease or stroke
• diabetes with complications
• disease of the liver
• risk factors for osteoporosis (thinning of the bones) (see Can I use a contraceptive injection if I am at risk of osteoporosis?)
• systematic lupus erythematosus.

What are the advantages of a contraceptive injection?

• You don’t have to think about contraception for as long as the injection lasts.
• 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 is a good method if you cannot use estrogens, like those in the combined pill, the contraceptive patch and the vaginal ring.

What are the disadvantages of a contraceptive injection?

• Your periods may change in a way that is not acceptable to you (see Will a contraceptive 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 a contraceptive injection?).
• The injection works for 12 or eight 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.
• There can be a delay of up to one year before the return of your periods and fertility after stopping the injection.
• 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. 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.
• You can have an allergic reaction to the injection, but this is 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. It does not cause an increase in bone fracture.
• Thinning of the bones may be more of a problem for women who already have risk factors for osteoporosis (see Can I use a contraceptive injection if I am at risk of osteoporosis?).
• Women under 18 years old may use Depo-Provera, but only after careful evaluation by a doctor. This is because young women under 18 are still making bone.

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

If you have risk factors for osteoporosis 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 menopause or early menopause (before 45 years)
• a lack of estrogen due to missing periods for six 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 website can give you more information.

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

It is not recommended that all women have a bone scan before they start a contraceptive injection. It may be useful for some women – usually those who have been identified as having risk factors for osteoporosis.

Will a contraceptive 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).
• 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 a contraceptive injection?

Depo-Provera is associated with an increase in weight of up to 3kg (6.6lbs) over two years.

When can I start using a contraceptive injection?

You can start a contraceptive injection any time in your menstrual cycle if it is certain that you are not pregnant. If you start the injection during the first five days of your period you will be protected against pregnancy immediately.

If you have it on any other day you will not be protected for the first seven days, so you will need to use additional contraception, such as condoms, during this time.

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

The injection can be started any time after you have given birth if you are not breastfeeding. If you start the injection before three weeks (21 days) you will be protected against pregnancy immediately. If it is started later than day 21 you will need to use an additional method of contraception for seven days.

If you are breastfeeding, the injection is usually given from six weeks after you have given birth. The injection can be started earlier if there are no other alternatives that you find acceptable. The injection can be used safely while you are breastfeeding and will not affect your milk supply.

Heavy and irregular bleeding is more likely to occur if you have the injection in the first few weeks after giving birth.

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

The injection can be started immediately after an abortion or miscarriage. You will be protected against pregnancy immediately.

Can anything make a contraceptive injection less effective?

While the injection is working nothing 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
• diarrhoea
• vomiting.

It is important to go back at the right time for your next injection – every 12 weeks for Depo-Provera or every eight weeks for Noristerat.

If you miss, or are late having, the next injection it may mean that you are no longer protected against pregnancy. To ensure that you remain protected against pregnancy you should not be more than two weeks late for your next injection.

Will I be able to choose which contraceptive 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 to become effective. Your doctor or nurse can discuss with you which contraceptive injection is most suitable.

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

Contraceptive injections are highly effective methods 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 do a pregnancy test or speak to your doctor or nurse as soon as possible. Using the contraceptive injection does not affect a pregnancy test.

If you do get pregnant while you are using the injection, there is no evidence that it will harm the baby.

How long can I use a contraceptive injection for?

You can continue to use Depo-Provera until you are 50 years old, provided there are no medical reasons not to use it and you are not at risk of osteoporosis (see How does Depo-Provera affect my bones? above).

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 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 a contraceptive injection. However, it is possible to get pregnant before 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.

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.

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

No. It is not necessary to stop a contraceptive 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 or want to ask any questions between injections, you should contact your doctor or nurse.

Last updated November 2012. Next update available October 2013.