The birth control pill

There are two kinds of contraceptive pill: the combined pill and the progestogen-only pill. But what does the pill do? What types of birth control pill are there? And, most importantly: does the pill actually work? Here’s what you need to know.

A young woman is playing pool. She is taking the pill.

What does the pill do?

There are differences between the combined pill and the progestogen-only pill which we’ll go into in a moment. Depending on which you take, the pill either prevents eggs from being released or makes it very difficult for sperm to reach the egg.

The combined pill contains two synthetic hormones, oestrogen and progestogen, that prevent the ovaries from releasing an egg each month (as well as thickening the mucus of your cervix to make it harder for sperm to travel).

The progestogen-only pill (aka POP or the mini-pill) contains only progestogen and is a useful alternative for women who are unable or unwilling to take oestrogen. Unlike the combined pill, the POP does not always prevent ovulation (AKA your period). Instead, it makes the mucus around the cervix thicker, which makes it difficult for sperm to get into the womb.

There are various brands offering different levels of hormones – your GP or nurse at the family planning clinic will work out which one’s best for you.

Does the pill stop your period?

The combined pill does not stop your period. Each month you’ll have seven days off where you’ll bleed like a regular period. The mini-pill, on the other hand, has no days off and can stop your period, although some people do continue to have them.

Does the pill work?

Both pills, when used correctly, can be over 99% effective in preventing pregnancy.

Why are there different kinds of pill?

Every woman is different. While some barely notice a change in their mood/weight/skin/eating habits every month there are others who could eat the entire contents of the Cadbury factory and rip the head off anyone who dares mention there’s a spot on the end of their nose. Unfortunately hormones are complicated, so finding the right pill is down to trial and error.

Both pills protect against pregnancy but not STIs, so always use a condom to minimise the risks.

Are there any side effects of the pill?

With the combined pill, some women experience temporary side effects such as headaches, nausea and weight gain. These shouldn’t last long – three months at the most – but if problems persist, talk to your doctor about trying a different brand. Find out more about the side effects of the pill here.

For the progestogen-only pill, most women notice changes to their menstrual cycle, and some may experience irregular bleeding and missed periods.

There is also a small increased risk of developing blood clots from any of the pills that contain oestrogen.

How is the pill taken?

The combined pill usually comes in packets containing 21 once-a-day tablets. This is followed by a pill-free seven days, when you get a period. After that, you start another packet.

The progestogen-only pill is taken every day at the same time with no break between finishing one pack and starting another. Women using the progestogen-only pill can usually expect their periods to continue, but must not stop taking their pill.

If you miss a day…

The combined pill

The progestogen-only pill

  • Missing one progestogen-only pill by more than three hours means you won’t be protected against pregnancy (except Cerazette which has a time window of 12 hours).
  • Take it as soon as you remember (even if you’ve missed it by 24 hours, in which case take two pills together).

If you throw up, or suffer from a bout of diarrhea

Both types of pill are absorbed through the digestive system. This means vomiting or getting the runs could compromise the hormone level required for effective contraception. To protect you against pregnancy, be sure to use condoms for seven days (as well as continuing your normal pill cycle).

Can anyone take the pill?

Most women can take the pill, but 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 why it may be unsuitable, these include:

  • If you think you’re pregnant, or think you may have had an ectopic pregnancy.
  • If you have cardiovascular conditions, liver disease or ovarian cysts.
  • If you have liver disease.
  • If you experience high blood pressure or severe migraines.
  • If you have a terrible sense of time (for the progestogen-only option).

Next Steps



By Nishika Melwani

Updated on 24-Jun-2022