First the Facts

  • An injection that contains a hormone to prevent pregnancy
  • 94% effective
  • Lasts for 13 weeks
  • Can be given in a specialist clinic or by yourself at home
  • Does not protect against sexually transmitted infections

How Does It Work?

  • The contraceptive injection contains progestogen which prevents your ovaries from releasing an egg (ovulation)
  • It also thickens the mucus at the cervix (neck of the womb), preventing sperm from entering
  • There are two types of contraceptive injection available in the UK: Depo-Provera® and Sayana® Press
  • Both are over 94% effective: approximately 6 per 100 users will fall pregnant within a year

Does It Work Straight Away?

The contraceptive injection does not always work straight away, it depends when it is given:

  • If the contraceptive injection is given within the first 5 days of your period, it will work straight away
  • If the contraceptive injection is given after day 5 of your period, you must use another contraceptive (e.g. condoms) for 7 days. This is because it will take 7 days for the contraceptive injection to start working
  • It works straight away if given within 21 days of childbirth and is completely safe if you choose to breastfeed. If it is given after this, you must use condoms for 7 days
  • It works straight away if given within 5 days of miscarriage or abortion. If it is given after this, you must use condoms for 7 days

Are There any Side Effects?

  • A change in bleeding occurs because of the mode of action of the contraceptive injection
  • You will no longer have ‘periods’ and we cannot predict what bleeding you will experience
  • Some women have no bleeding and this is safe and nothing to be concerned about
  • Other women have continual or irregular bleeding; if this happens to you, we can provide treatment to control it
  • On average, users experience less bleeding and it is less painful
  • Acne, breast tenderness, headaches, weight gain and mood changes can sometimes occur
  • In some users it can affect the strength of their bones
  • It may take up to a year to fall pregnant again after you have stopped using the contraceptive injection. Your long-term fertility will not be affected

How Is It Given?

  • Depo-Provera® is usually given by a nurse of doctor into the buttock or upper arm
  • Sayana® Press can be given by yourself at home. You will be taught how to administer the injection, normally into your tummy or upper leg
  • They are both given every 13 weeks. If given later than 14 weeks, you must use condoms for 7 days to allow the contraceptive injection to start working again

Where Can I Get the Contraceptive Injection?

You can get the contraceptive injection free of charge at:

  • A sexual health, genitourinary medicine or contraception clinic
  • Some young person’s clinics
  • Some GP surgeries

Is It Right for Me?

The contraceptive injection is safe to use in the majority of users; however, there are some circumstances where it may not be appropriate.

Always discuss with the doctor or nurse if:

  • There is a chance you are already pregnant
  • You have a history of breast cancer or liver disease
  • You have bleeding in between your periods or after sex which has not been investigated
  • You take medications that could interfere with the contraceptive injection (including over-the-counter or herbal remedies)


Written by: Dr David Rook and Dr Paula Briggs
Last updated: January 2021

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