This article on progesterone only, or mini pill, explains the advantages & disadvantages of the progesterone only pill as a contraceptive choice.

What is the progesterone only / mini pill?

This is a pill that is taken every day, by women, to prevent pregnancy. It contains only progesterone hormone (the combined pill contains progesterone and oestrogen). Progesterone is produced naturally by the body as part of the menstrual cycle and in greater amounts during pregnancy.

How does this pill work?

The progesterone in the mini pill has the effects of thickening the mucus in the cervix – which means that sperm are unable to pass through the mucus to find and fertilize the woman’s egg.

Also the progesterone changes the lining of the womb, so that even if an egg did get fertilized, it would be less likely to implant successfully causing a pregnancy.

Some women may also stop ovulating whilst they are on the mini pill, but this is not guaranteed.

Usually you will start the mini pill on the first day of your period and take it every day, without a break between packs. You will be safe to have sex immediately and for as long as you take you pill correctly. For the mini pill to be effective, you must take it at the same time every day. If you are more than 3 hours late, you need to use added contraception, such as condoms, for 2 days. Likewise if you have vomiting or diarrhoea you may not have absorbed the pill, so use added contraception for 2 days, or avoid intercourse.

If you commence the mini pill between periods you will not be protected from pregnancy for the first 7 days.

Where can you get mini pill from?

The mini pill is obtained by prescription from your family doctor or Family Planning Centre (FPC). It can also be obtained via your Lead Maternity Carer in the first 6 weeks after having a baby.

What types of progesterone only pill are available?

There are different brands of mini pill available. Your doctor will advise you which one to take and give you clear instructions on how to take it effectively.

How much does the mini pill cost?

The cost of the prescription for the mini pill will depend upon your age and whether or not you have a Community Service Card. For example if you are under 22 years it will cost $3 per script.

What is the success rate of the progesterone only pill in preventing pregnancy?

Studies show that it is 96-99% effective. This means that if 100 women take the mini pill correctly for one year, 1-4 will become pregnant.

Is this pill effective in preventing Sexually Transmitted Infections?

No, in order to prevent STIs it is necessary to use a condom and lubricant also.

What are the risks with the mini pill?

There is a slightly increased of an ectopic pregnancy whilst you are taking the mini pill. This is a pregnancy that has implanted outside the womb, for example in the fallopian tube. If you experience lower abdominal pain, while taking the progesterone only pill, contact your doctor immediately.

If you have had a previous ectopic pregnancy, your doctor may advise against you taking this pill.

What are the pros?

  • The mini pill is easy to use
  • It does not interrupt sexual intercourse
  • It is suitable for breastfeeding mothers, as it does not affect the milk supply. Remember it is possible to get pregnant whilst you are breast feeding.
  • The progesterone pill can be taken by women at any age.
  • Some women do not have any bleeding at all whilst they are on this pill.
  • Due to a lack of side effects, it can be taken by women who are not able to take the combined pill.
  • If you wish to have a baby, this pill will not affect your chances of conceiving after taking the pill. Remember that 1 in 10 couples have problems conceiving a baby, whether they were taking oral contraceptives or not.

What are the cons?

  • Some women experience irregular spotting, which can be a nuisance.
  • You must remember to take the pill within a 3 hour time period every day. It is not suitable for someone with a poor memory.

Useful articles and websites

Remember that the combined pill does not prevent you getting STIs. Visit our article Condomsfor more information on condoms and lubricants.

To find your local Family Planning Clinic in NZ visit- www.familyplanning.org.nz

To compare this contraception with the Combined Pill, click here

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Paula Skelton is a qualified NZ nurse and midwife, a midwifery & childbirth educator and the mum of three lovely girls.

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I’m on Cerazette and it works perfect for me! No periods, just VERY occasional light bleeding. Have been taking it for about 5 years and despite it being more expensive (not subsidized by our government) I am extremely happy with it.


I started this pill and then two weeks into it I got my period I am now on day 8 of my period and it has know signs of slowing or stopping. Is this normal?


hi this article does not mention change in weight like the others… does this mean i will not have an increase in appetite or gain weight if i start taking it?

Rochelle Gribble

Hi Gabby,

Weight gain is a less commonly reported side effect with the progesterone-only pill but it’s still possible. Different people respond differently and it’s impossible to say how your body will respond.

Hope that helps!


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