Deciding on birth control: the birth control pill.

There are 2 types of contraceptive pill – the progesterone-only pill (sometimes called the mini-pill or the POP) and the more common combined pill.  The combined birth control pill has oestrogen and progesterone in it and has been used as contraception since the 1960s.


We’re going to talk about the combined birth control pill in this article.

What is the Pill?

The combined pill is a combination of oestrogen and progesterone which cause several things to happen that prevent pregnancy:

  • Prevents an egg from being released from the ovary (ovulation)
  • Makes the mucus in the cervix thicker so that the sperm cannot get through the cervix to the egg
  • Makes the lining of the womb thinner so that any fertilized egg cannot settle (implant) into it.

What are the advantages of the birth control pill?

  • It doesn’t interfere with sex and is easy to use
  • It is very effective – over 99% effective when taken correctly (see below)
  • It’s easily reversible when you want to start a family
  • It can make pre-menstrual tension (PMT or PMS) better in some women
  • It can reduce your risk of pelvic infection as the thick mucous plug stops bacteria from getting into the womb.
  • It may reduce your risk of some forms of cancer – ovarian cancer, colon cancer and womb cancer.

What are the disadvantages of the Pill?

  • To be taken correctly, it must be taken at the same time every day.  It will be less effective if you miss a pill or take it more than 3 hours late.  See below for what to do if this happens.
  • It doesn’t protect you against sexually transmitted infections.
  • Some women say that they gain weight while on the Pill but this hasn’t been shown in scientific studies.

Is the birth control pill right for me?

  •  The Pill isn’t right for every woman and your doctor will talk you through the risks and benefits of taking it before s/he prescribes it.
  • It may not be right for you if you don’t have a regular routine so that you can take it at
  • Take your Pill at the same time every day.

  • the same time each day.  For example, if you do a lot of travelling where you change time zones, if you work irregular shifts or if you are forgetful, another choice of contraception might be better for you.
  • If you have a history of high blood pressure then the Pill might not be right for you as it can make the blood pressure increase.  You should have your blood pressure checked every 6 months or so while you’re on the birth control pill.
  • If you have a history or family history of blood clots in the legs or lungs, then the Pill may not be suitable for you.  There is a slight increased risk of blood clots in the general population of women on the Pill. But if you have a greater risk because you’ve had a clot before or have a close family member who’s had one, the Pill isn’t for you.

Other conditions where the Pill may not be right for you include:

  • Being very overweight
  • If you have/have had hepatitis or breast cancer
  • Being a heavy smoker (40 or more cigarettes a day)
  • Breast feeding
  • Being over 50 years of age
  • Having migraines.

What are the types of birth control pill?

There are a lot of different brands of Pill on the market.  They contain different levels and different types of progesterone and oestrogen.

Some are 21 day pills, where you take a pill at the same time every day for 21 days and then stop for 7 days.  During the time that you’re not taking a pill you will have a ‘withdrawal bleed’ which is like your menstrual period. You then take your first pill of the next pack on the same day each month.

Some are every day pills, where you take a pill at the same time every day without a break.  7 of the pills are dummy pills so they don’t contain any chemical, and you will have your period when you take those pills.  This type is good for people who don’t want to think about when they need to stop and start taking their birth control pills.

Some are phasic pills, which means that they contain varying levels of hormone in different parts of the pill-taking cycle.

The advantage of having lots of different types and brands of Pill is that if one doesn’t suit you for any reason you can try others.  Often it can be a trial and error to get the brand that suits you.  Your doctor or nurse will talk you through this process.

What are the side effects of the birth control pill?

Most women don’t have side effects from the Pill.  However some experience:

Mild headaches

Mild nausea (feeling sick)

Breast aches

Mood changes

Changes in sex drive

Changes in skin – acne etc

Rise in blood pressure.

What do I do if I miss a Pill?

Missing a pill, or taking it more than 3 hours late will make it less effective and make it more likely that you will become pregnant.

This is also true if you vomit within 3 hours of taking your pill or have very bad diarrhoea.  Mild diarrhea shouldn’t affect the Pill’s effectiveness.

Because there are so many different brands and types of birth control pill it’s important to read the information leaflet in the packet to find out what you should do if you miss one or more pills.

birth control pill

Pill or condom? BOTH. Protect against pregnancy AND disease.

The instructions also vary for when (which part of the month) you missed the pill in the cycle.

This may involve taking 2 pills in a day and may mean that you need to use additional contraception (eg using condoms).

If you’re in any doubt, take advice from your health care provider.

Find out more:

In the UK see

In the US see

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