Patient information from BMJ

Contraception: oral contraceptives (the pill)

Last published:Apr 25, 2022

The contraceptive pill has been around for a long time, and it can be very effective in preventing pregnancy. But some types of the pill are not suitable for everyone.

If you are interested in the pill as your preferred method of contraception, you can use our information to talk with your doctor about which type of pill is suitable for you. 

The right contraception for you

There are many types of contraception to choose from, including the contraceptive pill. But they are not all suitable for everyone.

For example, women with heart conditions might not be able to take the pill. And people allergic to latex won’t be able to use latex condoms.

The type of contraception that suits you best will depend on several things including:

• your medical history, including things like allergies and any health conditions that you have

• your lifestyle

• whether you need to think about preventing sexually transmitted infections (STIs), including HIV. For example, this applies to you if you have multiple partners, or if you change partners, and

• your own preferences: for example, you might not want to use some types of contraception because you’re concerned about side effects. Or maybe you don’t want to use condoms because you want something that you don’t want to have to think about 'in the moment'. 

What is the contraceptive pill?

The contraceptive pill is a pill that stops you getting pregnant. It works mainly by affecting your hormones so that you don’t release an egg from your ovaries (ovulate) during your period.

There are two types of contraceptive pill, which use different hormones. They are:

• the progestogen-only pill and

• the combined oestrogen/progestogen pill - usually called the combined contraceptive pill.

But there are many different brands of pill, often with different instructions about how to take them.

For example:

• some brands of pill come in packs of 21, which means you only take a pill for 21 days of your 28-day menstrual cycle. For the other 7 days, you will bleed as you would normally when having a period

• other brands come in packs of 28 pills, even though 7 of the pills don’t actually do anything, and you still bleed normally on the 7 days that you take these pills. 

These pills that don’t do anything are called 'placebo' pills. They are there to help you stay in the habit of taking your pills, and to help you avoid losing track of where you are in your cycle.

Your doctor or nurse should explain carefully how your pills work, including what to do if you miss a pill. And you should feel free to ask any questions you like, or to tell him or her if you are not clear about the instructions.

With both the progestogen-only and the combined pill, If you decide that you want to try to become pregnant, just stop taking them and your fertility will return to normal very soon. 

The combined contraceptive pill

The combined pill contains two hormones: one called a progestogen hormone, and one called oestrogen. The combined pill prevents pregnancy by:

• preventing the ovaries from releasing an egg each month

• thickening the mucus (fluid) in the cervix so that it’s harder for sperm to reach an egg, and

• thickening the wall of the uterus (womb) so that it’s harder for any fertilised egg to implant in the wall of the womb. If an egg can’t implant in this way, it can’t develop.

The combined pill works for about 99 women in 100 when it’s used properly. Using it properly usually means taking it at roughly the same time every day.

The combined pill can cause side effects in some women, including:

• irregular bleeding

• nausea

• tender breasts, and

• headaches. 

These side effects usually stop after a few months. But if they don’t, you can talk with your doctor about changing to a different pill. 

Who can take the combined pill?

The combined pill is not suitable for everyone. This is because there is a small chance that the oestrogen in the pill can cause serious health problems for some women, including strokes, heart attacks, and deep vein thrombosis (DVT).

Some women are wary of taking the combined pill because it slightly increases your chance of breast cancer. But it also slightly reduces your chance of getting endometrial cancer and ovarian cancer.

Your doctor can explain the cancer risks around the combined pill, and answer any other questions you have.

If you talk to a doctor or nurse about taking the pill, he or she should ask you about any other health conditions that you have, to make sure that you don’t take the combined pill if it’s not suitable for you.

You should not take the combined pill if you:

• smoke

• migraines with 'aura' (such flashing lights and problems with your vision)

• have any history of heart disease

• have had a stroke

• have severe liver disease

• have very high blood pressure

• have ever had deep vein thrombosis.

The progestogen-only pill

This pill uses only one type of hormone, called a progestogen. It can be very effective at preventing pregnancy. Like the combined pill, it works best when you take it at the same time every day.

There are different types of progestogen pill, which each use a different progestogen hormone. The progestogen pill is often taken by women who can’t take the combined pill.

There are many different brands of progestogen pill, and they vary slightly in how they should be used. Your doctor or nurse can explain to you exactly how to use the one that you are using.

Some women stop having their monthly periods while using this type of pill. There can be other side effects in some women, including:

• changes in bleeding patterns

• headaches

• mood changes, and

• tender breasts.

If you have unpleasant side effects, talk to your doctor about trying a different brand. 

Can hormonal contraception help with difficult periods?

Some women choose hormonal contraception methods, such as the pill, because they can help with various problems they have with their periods. Combined hormonal contraception, which contains oestrogen, seems to help the most.

These problems sometimes improve because women stop having periods completely when using hormonal contraception. Or it can just ease they symptoms of various problems, including:

• heavy or irregular bleeding

• premenstrual symptoms, such as headaches, bloating, and mood changes

• endometriosis

• menstrual migraines

• anaemia caused by heavy bleeding

• flares of rheumatoid arthritis during periods

• acne

• polycystic ovary syndrome (PCOS), and

• menopausal symptoms.

You can talk with your doctor about whether hormonal contraception might help you with problems to do with your periods. 

Why contraception matters

The number of unplanned pregnancies tells us how important it is for sexually active people to think about contraception. For example:

• in the UK about 30 in 100 pregnancies are unplanned, and

• in the US about 50 in 100 pregnancies are unplanned.

This is not always bad news, of course: just because a pregnancy is unplanned doesn’t mean it’s unwanted.

But many unplanned pregnancies end in abortions, which can cause emotional distress, and which carry physical health risks, such as infections.

The contraceptive pill can be very effective at preventing pregnancy, but it doesn’t suit everyone.

But whatever method you choose, planning and taking responsibility for contraception is vital if:

• you are a sexually active girl or woman who could become pregnant, and you do not wish to become pregnant

• you are a sexually active male having sex with females of childbearing age, and you wish to play a responsible part in avoiding an unwanted pregnancy

• you think that you might be at risk of HIV or other STIs (for example, if you have multiple sexual partners) and you want to use a method of contraception that protects against infection.

Very few methods of contraception are totally effective. But planning gives you the best chance of being in control of when and if you become pregnant.

Your doctor or practice nurse will be very happy to discuss contraception and family planning methods that best suit you.