The contraceptive injection

No one gets a jab just for laughs. So you wanna be clued up before you do it. Especially if that jab messes with your hormones. That’s what we’re gonna help you with by answering questions like can you un-do it if you don’t like it? Here’s what you need to know about the contraceptive injection.

A young woman is sitting at a desk. She is thinking about the contraceptive injection.

What is the contraceptive injection?

The contraceptive injection works in basically the same way as the progestogen-only pill. That is, by stopping the ovaries releasing eggs and thickening the cervical mucus to make it virtually impossible for sperm to get through. As an added bonus, it also thins the lining of the womb. So if a particularly plucky sperm does manage to fertilise an egg, it’ll have nothing to hold onto.

There is one major advantage on the injection side of the pill vs injection debate, however – you don’t have to take a pill everyday (or for 21 days, then 7 days off in the case of the combined pill). Ideal for the less organised/forgetful among us. The only obvious downside is having to take a shot.

There are two types of injection available in the UK: Depo-Provera, which lasts for three months, and Noristerat, which lasts for two months. Both methods are over 99% effective.

Does the injection hurt?

Unless you have the world’s toughest skin, it does sting a bit and you may feel a bit bruised afterwards. But really that’s it. The whole ordeal is over in less than ten seconds. We should also mention that it’s injected into the muscle – usually on your bum or upper arm. Your bum is said to be less painful. So speak up if you have a preference.

You usually have one at any time. If you have it during the first five days of your period you’re protected straight away. On the other hand, if you have it any other time of the month you’ll still need to use condoms for at least seven days. It’s not an emergency contraceptive so speak to your doctor about any precautions you need to take while the injection takes effect.

Will the injection make my periods worse or stop them?

As with any hormonal contraception, it’s likely to have an impact on your menstrual cycle. You could get anything from irregular periods and possibly heavy bleeding, to lighter or non-existent periods. Unfortunately there’s no way of knowing how the injection will affect your unique body until you try it.

Annoying as this period lottery sounds, your cycle should settle down after a few months. And after a year’s use your period could even stop all together. This may seem worrying, but there’s nothing abnormal about it. In fact, it happens to roughly 70% of users.

Will I put on weight if I have the injection?

We’re not going to lie to you, for some inexplicable reason the answer is probably yes. But, before you start panicking, you’re unlikely to gain LOADS.

“When you look at the average weight gain we’re talking about small numbers (7lbs over 2 years). Strangely enough, no one’s come up with a sensible evidence-based reason for it,” says Lynn Hearton at FPA. “Your choice might depend on where you are on the weight scale before you start using it/ So it’s a question of considering the pros and the cons and working out what’s best for you.”

What if I hate it?

Unfortunately there’s no antidote for the contraceptive injection. This means that any side effects are there to stay until the jab wears off – and possibly for some time afterwards. Needless to say, it’s a pretty big commitment. 

How long does the contraceptive injection last? 

It varies from person to person, but normally between five to six months after you stop the injection. In rare cases it can take up to two years before fertility returns. Regardless, make sure to talk to your doctor if you have any concerns.

Are there any risks or side effects?

There’s a small risk of an infection at the site of the injection and, very rarely, some people can have an allergic reaction.

More long-term risks, such as links to breast cancer and osteoporosis, are speculative right now and research is ongoing.

The Royal Osteoporosis Society says: “Several studies have shown that bone density does decrease by a small amount in women using Depo-Provera,” thing is, most of that decrease happens after the first few years of use, then bone density stabilises. But it’s still something to consider if thinning of the bones is a concern of yours. Especially if you have a family history of the disease.

Anything else to worry about?

You have to remember to get the shot every two to three months. If you forget, or can’t make an appointment, you’ll lose your protection. Simple as that. Then it’s back to relying on the old rubber.

And remember, this method of birth control only prevents pregnancy, NOT STIs. So make sure you’re both tested before you chuck the condoms in the bin.

Can anyone have the injection?

Most people can have the injection. Nevertheless, your GP or nurse at the family planning clinic will go through your medical history to make sure it’s suitable for you. There are a few reasons we wanna highlight as to why it may be unsuitable for you. These include:

  • If you think you’re pregnant
  • If you have breast cancer or undiagnosed breast lump
  • If you have liver disease

Still looking for sexual health advice? Check out the rest of The Mix’s safe sex resources here. And if you can’t decide between the pill or injection? Check out our article ‘what contraception is best for me’ here.

Next Steps

  • FPA give sexual health advice. For Northern Ireland helpline call 0345 122 8687.
  • Brook's Contraception tool helps you work out best contraceptive method for you.
  • Chat about this subject on our Discussion Boards.
  • Need help but confused where to go locally? Download our StepFinder iPhone app to find local support services quickly.

By Nicola Scott

Updated on 29-Jun-2022