First the Facts

  • Progestogen-only pills (POPs) contain a single hormone
  • There are different types of the hormone progestogen in different pills
  • Older or traditional POPs are used less frequently for two reasons:
    1. They work by thickening the mucus at the neck of the womb and most women will continue to ovulate (produce an egg which could be fertilized). This increases the risk of the method failing
    2. Pills must be taken within a three-hour window to optimize contraceptive effectiveness
  • POPs containing a progestogen called desogestrel are as effective as the combined pill
    • Less than 1% risk of the method failing (as long as the pills are taken correctly)
    • One pill should be taken every day without a break
    • There is a 12-hour window, i.e., if you normally take your pill at 6 pm, as long as you take it before 6 am the following day, there will be no loss of effectiveness
  • There are very few reasons why POPs cannot be safely used
  • POPs do not protect against sexually transmitted infections

How Does It Work?

  • POPs contain a hormone called progestogen
  • Progestogen thickens the mucus at the neck of the womb, preventing sperm passing through the cervix into the womb and out to the fallopian tube where fertilization takes place if an egg has been released
  • POPs containing a desogestrel also inhibit ovulation, and no egg is released. This is a more reliable way of preventing pregnancy
  • Desogestrel thins the lining of the womb, creating an environment where a fertilized egg would be unlikely to thrive. This means that if everything else failed and fertilization did occur, a viable pregnancy would be highly unlikely
  • POPs containing 75 micrograms of desogestrel can have different names
    • Look out to see what is in the pill and don’t worry about the name. As long as the hormonal content is the same it is OK to switch between brands

Does It Work Straight Away?

The POP does not always work straight away. This depends on when it is started:

  • If the POP is started within the first 5 days of your period, it will work straight away
  • If it is started at any other time, you must use another contraceptive method (e.g. condoms) for 48 hours. This is because it will take 48 hours for the POP to become effective
  • It works straight away if commenced within 21 days of childbirth and is completely safe if you choose to breastfeed
  • If you have had unprotected sex and there is a risk of pregnancy, you can commence the POP, but take a pregnancy test 21 days after the most recent episode of unprotected sex
  • It works straight away if commenced within 5 days of miscarriage or abortion. If it is commenced after this, you must use condoms or abstain for 48 hours

Are There any Side Effects?

Desogestrel POPs

  • A change in bleeding occurs with desogestrel POPs because of the mode of action (prevention of ovulation)
  • You will no longer have ‘periods’ and most women stop bleeding, but this can take around twelve months. In the intervening period you are likely to experience irregular bleeding
  • Most women experience less bleeding and pain
  • Women are unlikely to experience any change in bleeding pattern with traditional POPs
  • Acne, breast tenderness, headaches and mood changes can sometimes occur with any POP
  • Future fertility is not affected by the POP; you can become pregnant as soon as the method is discontinued. Another method of contraception should be commenced if you do not wish to become pregnant.

Special Considerations

  • Vomiting and diarrhoea can affect absorption of your pill and additional precautions should be used whilst you are experiencing symptoms and for 48 hours after recovery
  • Enzyme-inducing drugs can affect metabolism of your pill. This can reduce how effective it is, and you should check with a doctor, nurse or pharmacist if you are prescribed any new medication
  • Some herbal remedies can also increase metabolism and increase the failure rate of your contraceptive pill
  • The POP can be used until age 55
  • There are some non-contraceptive benefits associated with use, such as a control of heavy and/or painful periods
  • Hormone tests can be taken to see whether you are menopausal without stopping your pill

Where Can I Get Supplies of POPs?

You can get POPs free of charge at:

  • A sexual health, genitourinary medicine or contraception clinic
  • Young person’s clinics
  • GP surgeries
  • POPs are also available online, but you may have to pay for them
  • Once you are happy with the method, a twelve-month supply can be provided at a time

Is the POP Right for Me?

The POP 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 severe liver disease
  • You have bleeding in between your periods or after sex which has not been investigated
  • You take medications that could interact with the POP (including over-the-counter or herbal remedies)


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

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