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The Contraceptive Injection

The Contraceptive Injection

Contraceptives effectiveness stat
Contraceptives effectiveness stat
The contraceptive injection can be a great alternative to the contraceptive pill - especially for people who are forgetful. Just like the contraceptive pill, it contains hormones which prevent pregnancy. Instead of having to take the hormones as tablets every day, women who use the contraceptive injection visit their GP for a jab which lasts a number of months.

Last reviewed: 14/11/2019 by Dr Clair Grainger

Contents

How does the contraceptive injection work?

The most common injection used in the UK is intramuscular medroxyprogesterone acetate (otherwise known as Depo-Provera). The contraceptive injection works just like a mini pill. It contains a progesterone (a type of sex hormone) which:

  • thickens the mucus at the entrance to the womb (so sperm can’t get in)
  • prevents ovulation (the release of an egg)
  • makes it more difficult for a fertilised egg to implant by changing the lining of the womb
That it works in three ways means that even if one of these mechanisms should fail, you are still protected from pregnancy. In fact, the contraceptive injection is over 99% effective if injections are on time, which means that less than one in 100 women who use it get pregnant within a year. Sometimes it can be difficult to remember to have the injection on time so the overall effectiveness of the injection at preventing pregnancy is actually around 94%. The contraceptive pill is just as effective if used correctly but its effectiveness is diminished if you forget a tablet. With the Depo-Provera injection, all you have to remember is the regular visit to your GP, every 12 weeks.

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Which types of injections are there?

The two most common contraceptive injections in the UK are called Depo Provera and Noristerat. Most women who use the injection are on Depo Provera.

Depo Provera

Depo Provera is a contraceptive injection which prevents pregnancy for 12 - 14 weeks. You have to have your repeat injection after 12 weeks and it’s important that you get it on time. You should have the first injection within the first 5 of your period. This way, you will be protected immediately. Otherwise you would need to use condoms for the first 7 days after your injection. Sayana Press is another injection which contains the same hormone as Depo Provera but is given under the skin rather than into the muscle. 

Noristerat

Noristerat contains a different progesterone than Depo Provera. It is not as commonly prescribed because it only protects you for 8 weeks, after which the injection has to be repeated.

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Does the injection cause any side effects?

Like all hormonal contraceptives, the injection can cause side effects.

Possible side effects of the contraceptive injection:
  • headache
  • abdominal pain
  • weight gain
  • nausea or bloating
  • dizziness
  • acne and other skin problems
  • fluid retention
  • weakness
  • irregular bleeding or spotting 
  • vaginal discharge
  • breast tenderness or pain
  • changes affecting your mood and sex drive
  • thinning of the bones
In addition, once you stop taking the contraceptive injection, it may take up to a year for your periods and fertility to return to normal.

For all possible side effects of the contraceptive injection, read the patient leaflets for Depo Provera, Sayana Press or Noristerat.

The injection is not suitable for everyone and your doctor will have a consultation with you to determine whether you can use it or not. It is not suitable if you:

  • are pregnant
  • have or have had breast cancer
  • suffer from vaginal bleeding between periods
  • have problems with your arteries (including if you have had a heart attack or stroke)
  • have or have had liver cancer or severe liver disease
  • are allergic to any of the ingredients
It may not be suitable for you if you suffer with certain other medical conditions so you should always chat to your doctor before starting this. 

Does the contraceptive injection cause weight gain?

In some women, the contraceptive injection causes weight gain. Clinical trials for Depo Provera showed, that the average weight gain over 1–2 years of using the injection was 5–8lbs. Women who used the injection over 4–6 years gained 14–16.5lbs on average. This side effect does not affect all women.

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Advantages and Disadvantages

What are the advantages?

The biggest advantage of the contraceptive injection is convenience – all you need to do is get the injection every 12 weeks. This makes the jab a very safe and reliable contraceptive. Although it is only as effective as the pill on paper, in reality it tends to be safer as some women forget to take the pill on time now and then. It can also cause lighter or less frequent periods and may offer some protection against cancer of the uterus and ovaries.

It is possible to use the contraceptive injection during breastfeeding.

What are the disadvantages?

Although it is very convenient, the injection also has disadvantages:

  • You can’t change your mind - Once you have been given the injection, the active ingredient will be in your body for two to three months. You will not be able to get pregnant in that time and if you suffer side effects, they may persist until the 8 or 12 weeks are over
  • You have to visit your GP every time your injection is due
  • You should not have it if you want to have a baby in the coming year as you might not ovulate for a while after you have stopped having injections
  • There is also a possible weak link between developing breast or cervical cancer and using the injection, though this risk is likely to reduce after stopping the injection.

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Sources

Depo-Provera (2020) EMC [last accessed 31 March 2020]

Noristerat (2019) EMC [last accessed 31 March 2020]

Progesterone-only injectable (2019) FSRH [last accessed 31 March 2020]

Sayana Press (2019) EMC [last accessed 31 March 2020]

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Important Questions

Do I still need to use a condom?

Yes - every time you have sex with someone whose STI-status you do not know. The injection does not protect you from sexually transmitted diseases such as chlamydia, herpes or HIV.

Can I get pregnant as soon as I stop using the injection?

It is possible, so you should use extra contraception if you do not want to become pregnant. However, you shouldn’t choose the injection if you want to have a baby in the near future. It can take up to a year before you are fertile again.

Is the injection suitable for all women?

No. Whether you can use a contraceptive injection depends on your age, health and lifestyle. Women with certain medical conditions, for example liver problems, breast cancer, osteoporosis or a disease of the arteries cannot use it. Your GP will need to check your medical history carefully before prescribing the injection.

Is the injection suitable for women of all ages?

No. The contraceptive injection lowers your levels of oestrogen and it can decrease the density of your bones. For this reason, it is not recommended for women under the age of 18 or over 50, unless no other option is acceptable.

Can I continue using the injection over many years?

Because it can cause thinning of the bones, the injection should not be used permanently without careful consideration of the benefits and risks. If you are planning to use it for more than two years, you should discuss the risks with your prescribing doctor. 

What do I do if my injection is late?

If it has been 14 weeks or more since your last Depo-Provera or Sayana Press injection or 10 weeks or more since your last Noristerat injection and you have unprotected sex then emergency contraception is needed to prevent pregnancy. 

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