# The contraceptive injection

> A jab every few months – plus the bits worth knowing before you choose it.

Category: Contraception · 4 min read · Written by the Splash team · Sources checked October 2026
URL: https://splash.care/learn/contraception/injection

## Quick answer

- One injection lasts 8–13 weeks depending on type.
- Over 99% if on time, 94% typically.
- Fertility can take up to a year to come back.
- Long-term use can temporarily affect bone density.

The injection contains [Progestogen](https://splash.care/learn/glossary/progestogen) and stops [ovulation](https://splash.care/learn/glossary/ovulation). Depending on the type (such as Depo-Provera, Sayana Press or Noristerat), it lasts 8 to 13 weeks.

**94%** Typical-use effectiveness (over 99% if every jab is on time)

## Good to know before choosing

- Fertility can take up to a year to return after stopping – not ideal if you’re planning a baby soon
- Using it for more than a year can weaken bones; they’re expected to recover after you stop
- Weight gain is a common side effect
- Periods often become [irregular](https://splash.care/learn/cycle-basics/irregular-cycles) or stop – the longer you use it, the more likely they stop
- Slightly raised breast and cervical cancer risk, and a small raised risk of a non-cancerous brain tumour called a meningioma – all very small, and the NHS says the risk is likely to fall after you stop

## Timing your next jab

Depo-Provera and Sayana Press are due every 13 weeks, and UK sexual health services allow a small safety margin: up to 14 weeks after your last jab is still fine. After that, tell a nurse, pharmacist or clinic straight away. You may need condoms, a [pregnancy test](https://splash.care/tools/pregnancy-test-timing) or [emergency contraception](https://splash.care/learn/glossary/emergency-contraception). Sayana Press can also be injected under the skin by yourself once a trained professional has shown you how, if that suits you better.

> **Splash says:** book your next jab before you leave the clinic. Late injections are where most real-life failures happen.

**Myth:** If your periods stop on the injection, something is wrong.

**Fact:** Periods stopping is a common, expected effect of the injection and isn’t harmful.

### When to see a doctor

See a GP, nurse or sexual health clinic as soon as you can if you’re more than 14 weeks since your last Depo-Provera or Sayana Press jab (you may need condoms or emergency contraception), if bleeding is heavy or prolonged, or if you have risk factors for weak bones.

> Only condoms (external and internal) help protect against STIs. Every other method on this page prevents pregnancy only.

## Sources

1. [NHS – What is the contraceptive injection?](https://www.nhs.uk/contraception/methods-of-contraception/contraceptive-injection/what-is-it/)
2. [NHS – Side effects and risks of the injection](https://www.nhs.uk/contraception/methods-of-contraception/contraceptive-injection/side-effects-and-risks/)
3. [NHS – How well contraception works at preventing pregnancy](https://www.nhs.uk/contraception/choosing-contraception/how-well-it-works-at-preventing-pregnancy/)
4. [ACOG – Progestin-only hormonal birth control: pill and injection](https://www.acog.org/womens-health/faqs/progestin-only-hormonal-birth-control-pill-and-injection)

This is general information, not medical advice. Splash can’t diagnose. If you’re worried, talk to a GP, pharmacist or sexual health clinic. In an emergency call 999 (UK) or 911 (US).