The combined oral contraceptive pill is usually just called "the pill". It contains artificial versions of the female hormones oestrogen and progesterone, which women produce naturally in their ovaries.
A woman can get pregnant if a man’s sperm reaches one of her eggs (ova). Contraception tries to stop this happening by keeping the egg and sperm apart or by stopping egg production. One method of contraception is the combined pill.
The hormones in the pill prevent your ovaries from releasing an egg (ovulating). They also make it difficult for sperm to reach an egg, or for an egg to implant itself in the lining of the womb. The pill is usually taken to prevent pregnancy, but can also be used to treat painful periods, heavy periods, premenstrual syndrome (PMS) and endometriosis.
At a glance: the combined pill
- When taken correctly, the pill is over 99% effective at preventing pregnancy. This means that fewer than one woman in 100 who use the combined pill as contraception will get pregnant in one year.
- You need to take the pill every day for 21 days, then stop for seven days, and during this week you have a period-type bleed. You start taking the pill again after seven days.
- You need to take the pill at the same time every day. You could get pregnant if you don't do this, or if you miss a pill, or vomit or have severe diarrhoea.
- If you have heavy periods or painful periods, the combined pill can help.
- Minor side effects include mood swings, breast tenderness and headaches.
- There is no evidence that the pill makes women gain weight.
- There's a very low risk of serious side effects, such as blood clots and cervical cancer.
- The combined pill is not suitable for women over 35 who smoke, or women with certain medical conditions.
- The pill does not protect against sexually transmitted infections (STIs), so using a condom as well will help to protect you against STIs.
How the combined pill works
How it prevents pregnancy
The pill prevents the ovaries from releasing an egg each month (ovulation). It also:
- thickens the mucus in the neck of the womb, so it is harder for sperm to penetrate the womb and reach an egg
- thins the lining of the womb, so there is less chance of a fertilised egg implanting into the womb and being able to grow
Although there are many different brands of pill, there are three main types:
Monophasic 21-day pills
This is the most common type. Each pill has the same amount of hormone in it. One pill is taken each day for 21 days and then no pills are taken for the next seven days. Microgynon, Brevinor and Cilest are examples of this type of pill.
Phasic 21-day pills
Phasic pills contain two or three sections of different coloured pills in a pack. Each section contains a different amount of hormones. One pill is taken each day for 21 days and then no pills are taken for the next seven days. Phasic pills need to be taken in the right order. Binovum and Logynon are examples of this type of pill.
Every day (ED) pills
You can get contraception at:
- most doctor surgeries
- community contraception clinics
- some GUM clinics
- sexual health clinics
- some young people's services
There are 21 active pills and seven inactive (dummy) pills in a pack. The two types of pill look different. One pill is taken each day for 28 days with no break between packets of pills. Every day pills need to be taken in the right order. Microgynon ED and Logynon ED are examples of this type of pill.
Follow the instructions that come with your packet. If you have any questions about how to take the pill, ask your doctor, nurse or pharmacist. It's important to take the pills as instructed, because missing pills or taking them at the same time as certain medicines may make them less effective.
How to take 21-day pills
- Take your first pill from the packet marked with the correct day of the week, or the first pill of the first colour (phasic pills).
- Continue to take a pill at the same time each day until the pack is finished.
- Stop taking pills for seven days (during these seven days you will get a bleed).
- Start your next pack of pills on the eighth day, whether you are still bleeding or not. This should be the same day of the week as when you took your first pill.
How to take every day pills
- Take the first pill from the section of the packet marked "start". This will be an active pill.
- Continue to take a pill every day, in the correct order and preferably at the same time each day, until the pack is finished (28 days).
- During the seven days of taking the inactive pills, you will get a bleed.
- Start your next pack of pills after you have finished the first, whether you are still bleeding or not.
Starting the combined pill
Most women can start the pill at any time in their menstrual cycle. There is special guidance if you have just had a baby, abortion or miscarriage. You may need to use additional contraception during your first days on the pill – this depends on when in your menstrual cycle you start taking it.
If you start the combined pill on the first day of your period (day one of your menstrual cycle) you will be protected from pregnancy straight away. You will not need additional contraception.
If you start the pill on the fifth day of your period or before, you will still be protected from pregnancy straight away, unless you have a short menstrual cycle (your period is every 23 days or less). If you have a short menstrual cycle, you will need additional contraception, such as condoms, until you have taken the pill for seven days.
If you start the pill on any other day of your cycle, you will not be protected from pregnancy straight away and will need additional contraception until you have taken the pill for seven days.
Taking pill packs back-to-back
For monophasic combined pills (pills all the same colour and with the same level of hormones), it is normally fine to start a new pack of pills straight after your last one – for example, if you want to delay your period for a holiday.
However, avoid taking more than two packs together unless advised to by a doctor or nurse. This is because you may have breakthrough bleeding as the womb lining sheds slightly. Some women find they feel bloated if they run several packs of the pill together.
What to do if you miss a pill
If you miss a pill or pills, or you start a pack late, this can make the pill less effective at preventing pregnancy. The chance of getting pregnant after missing a pill or pills depends on:
- when the pills are missed
- how many pills are missed
A pill is late when you have forgotten to take it at your usual time. You have missed a pill when it is more than 24 hours since the time you should have taken it. Missing one pill anywhere in your pack or starting the new pack one day late isn’t a problem, as you will still be protected against pregnancy (known as having contraceptive cover).
However, missing two or more pills, or starting the pack two or more days late (more than 48 hours late) may affect your contraceptive cover. In particular, if you make the seven-day pill-free break longer by forgetting two or more pills, your ovaries might release an egg and there is a risk of getting pregnant. This is because your ovaries are not getting any effect from the pill during the seven-day break.
If you miss a pill, follow the advice below. If you are not sure what to do, continue to take your pill and use another method of contraception, such as condoms, and seek advice as soon as possible.
If you have missed one pill, anywhere in the pack:
- take the last pill you missed now, even if it means taking two pills in one day
- continue taking the rest of the pack as usual
- you don’t need to use additional contraception, such as condoms
- take your seven-day pill-free break as normal
If you have missed two or more pills (you are taking your pill more than 48 hours late) anywhere in the pack:
- take the last pill you missed now, even if it means taking two pills in one day
- leave any earlier missed pills
- continue taking the rest of the pack as usual and use an extra method of contraception for the next seven days
- you may need emergency contraception
- you may need to start the next pack of pills without a break (see Starting the next pack after missing two or more pills)
You may need emergency contraception if you have had unprotected sex in the previous seven days and have missed two or more pills (you are taking your pill more than 48 hours late) in the first week of a pack.
Get advice from your contraception clinic, doctor or pharmacist about this.
Starting the next pack after missing two or more pills
If there are seven or more pills left in the pack after the last missed pill:
- finish the pack
- have the usual seven-day break
If there are fewer than seven pills left in the pack after the last missed pill:
- finish the pack and start the new one the next day, without having a break
Vomiting and diarrhoea
If you vomit within two hours of taking the combined pill, it may not have been fully absorbed into your bloodstream. Take another pill straight away and the next pill at your usual time.
If you continue to be sick, keep using another form of contraception while you're ill and for two days after recovering.
Very severe diarrhoea (six to eight watery stools in 24 hours) may also mean that the pill doesn't work properly. Keep taking your pill as normal, but use additional contraception, such as condoms, while you have diarrhoea and for two days after recovering.
Speak to your doctor or contraception nurse for more information, or if your sickness or diarrhoea continues.
Who can use the combined pill
If there are no medical reasons why you cannot take the pill and you do not smoke, you can take the pill until your menopause. However, the pill is not suitable for all women. To find out whether the pill is right for you, talk to your doctor, practice nurse or pharmacist.
You should not take the pill if you:
- are pregnant
- smoke and are 35 or older
- stopped smoking less than a year ago and are 35 or older
- are very overweight
- take certain medicines (ask your doctor about this)
You should also not take the pill if you have (or have had):
- thrombosis (a blood clot)
- a heart abnormality or heart disease, including high blood pressure
- severe migraines, especially with aura (warning symptoms)
- breast cancer
- disease of the gallbladder or liver
- diabetes with complications or diabetes for the past 20 years
After having a baby
If you have just had a baby and are not breastfeeding, you can start the pill on day 21 after the birth. You will be protected against pregnancy straight away. If you start the pill later than 21 days after giving birth, you will need additional contraception (such as condoms) for the next seven days.
If you are breastfeeding a baby less than six months old, taking the pill can reduce your flow of milk. It is recommended that you use a different method of contraception until you stop breastfeeding.
After a miscarriage or abortion
If you have had a miscarriage or abortion, you can start the pill up to five days after this and you will be protected from pregnancy straight away. If you start the pill more than five days after the miscarriage or abortion, you'll need to use additional contraception until you have taken the pill for seven days.
Advantages and disadvantages
Some advantages of the pill include:
- it does not interrupt sex
- it usually makes your bleeds regular, lighter and less painful
- it reduces your risk of cancer of the ovaries, womb and colon
- it can reduce symptoms of PMS
- it can sometimes reduce acne
- it may protect against pelvic inflammatory disease
- it may reduce the risk of fibroids, ovarian cysts and non-cancerous breast disease
Some disadvantages of the pill include:
- it can cause temporary side effects at first, such as headaches, nausea, breast tenderness and mood swings – if these do not go after a few months, it may help to change to a different pill
- it can increase your blood pressure
- it does not protect you against sexually transmitted infections
- breakthrough bleeding and spotting is common in the first few months of using the pill
- it has been linked to an increased risk of some serious health conditions, such as thrombosis (blood clots) and breast cancer
The combined pill with other medicines
Some medicines interact with the combined pill and it doesn't work properly. Some interactions are listed on this page, but it is not a complete list. If you want to check your medicines are safe to take with the combined pill, you can:
- ask your doctor, nurse or pharmacist
- read the patient information leaflet that comes with your medicine
The antibiotics rifampicin and rifabutin (which can be used to treat illnesses including tuberculosis and meningitis) can reduce the effectiveness of the combined pill. Other antibiotics do not have this effect.
If you are prescribed rifampicin or rifabutin, you may need additional contraception (such as condoms) while taking the antibiotic. Speak to your doctor or nurse for advice.
Epilepsy and HIV medicines, and St John's wort
The combined pill can interact with medicines called enzyme inducers. These speed up the breakdown of progestogen by your liver, reducing the effectiveness of the pill.
Examples of enzyme inducers are:
- the epilepsy drugs carbamazepine, oxcarbazepine, phenytoin, phenobarbital, primidone and topiramate
- St John's wort (a herbal remedy)
- antiretroviral medicines used to treat HIV (research suggests that interactions between these medicines and the progestogen-only pill can affect the safety and effectiveness of both)
Your doctor or nurse may advise you to use an alternative or additional form of contraception while taking any of these medicines.
Risks of taking the combined pill
There are some risks associated with using the combined contraceptive pill. However, these risks are small and, for most women, the benefits of the pill outweigh the risks.
The oestrogen in the pill may cause your blood to clot more readily. If a blood clot develops, it could cause deep vein thrombosis (clot in your leg), pulmonary embolus (clot in your lung), stroke or heart attack. The risk of getting a blood clot is very small, but your doctor will check if you have certain risk factors that make you more vulnerable before prescribing the pill.
The pill can be taken with caution if you have one of the risk factors below, but you should not take it if you have two or more risk factors. These include:
- being 35 years old or over
- being a smoker or having quit smoking in the past year
- being very overweight (in women with a BMI of 35 or over, the risks of using the pill usually outweigh the benefits)
- having migraines (you should not take the pill if you have severe or regular migraine attacks, especially if you get aura or a warning sign before an attack)
- having high blood pressure
- having had a blood clot or stroke in the past
- having a close relative who had a blood clot when they were younger than 45
- being immobile for a long time – for example, in a wheelchair or with a leg in plaster
Research is ongoing into the link between breast cancer and the pill. Research suggests that users of all types of hormonal contraception have a slightly higher chance of being diagnosed with breast cancer compared with women who do not use them. However, 10 years after you stop taking the pill, your risk of breast cancer goes back to normal.
Research has also suggested a link between the pill and the risk of developing cervical cancer and a rare form of liver cancer. However, the pill does offer some protection against developing endometrium (lining of the womb) cancer, ovarian cancer and colon cancer.