Combined contraceptive pill

Page last reviewed: 13/07/2011

The combined oral contraceptive pill is usually just called the pill. It contains synthetic (artificial) versions of the female hormones oestrogen and progesterone, which women produce naturally in their ovaries.

The Pill is usually taken to prevent pregnancy, but it can also be used to treat:

  • painful periods
  • heavy periods 
  • premenstrual syndrome
  • endometriosis 

How effective is it?

When taken correctly, the pill is over 99% effective at preventing pregnancy. This means that less than 1 woman in every 100 will get pregnant in a year.

How the pill works

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

Types of combined pill

Although there are many different brands of pill, there are three main types:

  • Monophasic 21-day pills (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. Examples are Microgynon, Brevinor and Cilest.
  • 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. Examples are Binovum and Logynon.
  • Every Day (ED) pills. There are 21 active pills and 7 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. Examples are Microgynon ED and Logynon ED.

Page last reviewed: 13/07/2011

Not everyone can use the combined oral contraceptive pill (the pill). You will need to talk to your doctor or nurse about your medical history.

When to avoid it

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 GP 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
  • breast cancer
  • disease of the gallbladder or liver
  • diabetes with complications or diabetes for the last 20 years

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.

Advantages

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 the symptoms of premenstrual syndrome.
  • 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.

Disadvantages

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.
  • Vomiting, diarrhoea, antibiotics and some other prescribed drugs can interfere with its effectiveness. In all instances another method of contraception would have to be used. Talk to your GP or local family planning clinic for further advice.

Page last reviewed: 13/07/2011

Starting the first pack of pills

The combined oral contraceptive pill (the pill) can be started at any time in your menstrual cycle.

It is usually started on the first day of your period (day one of your menstrual cycle). In this case, you will be protected from pregnancy straight away and will not need additional contraception.

If you start the pill up to and including the fifth day of your period, 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.

After having a baby

If you have just had a baby and are not breastfeeding, the pill can be started 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 to use additional contraception (such as condoms) for the next seven days.

If you are breastfeeding a baby under 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, the pill can be started up to seven days after this and you will be protected from pregnancy straight away. If started more than seven days after the miscarriage or abortion, use additional contraception until you have taken the pill for seven days.

How to take the pill

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.

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.

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 your GP. This is because the womb lining continues to build up and you may have breakthrough bleeding as it sheds slightly. Also, some women find they feel very bloated if they run several packs of the pill together.

Vomiting and diarrhoea

If you vomit within two hours of taking a pill, it may not have been fully absorbed into your bloodstream. Take another pill straight away and the next pill at your usual time. You should still be protected from pregnancy.

However, if you continue to be sick, you may not be protected from pregnancy.
Very severe diarrhoea (six to eight watery stools in 24 hours) may also reduce the effectiveness of the pill. Keep taking your pill as normal but use additional contraception while you have diarrhoea.

Speak to your GP or family planning nurse .

Page last reviewed: 13/07/2011

The combined oral contraceptive pill (the pill) is generally well tolerated, but there are some possible side effects.

Breakthrough bleeding and spotting is common in the first few months of taking the pill.

Other temporary side effects may occur after first starting the pill, including:

  • breast tenderness and breast enlargement
  • mood changes
  • an increased or decreased libido (sex drive)
  • fluid retention
  • headaches
  • nausea
  • rise in blood pressure

If these do not stop within a few months, changing the type of pill may help.

There is no evidence that the pill causes women to gain weight.

Page last reviewed: 13/07/2011

The combined contraceptive pill (the pill) can interact with other medicines. Some of the more common interactions are listed below. However, this is not a complete list.

If you want to check that your medicines are safe to take with the pill, ask your doctor or pharmacist, or read the patient information leaflet that comes with your medicine.

Antibiotics

The following antibiotics reduce the effectiveness of the pill:

  • rifampicin
  • rifabutin

Rifampicin is used to treat conditions such as tuberculosis, and can be prescribed for several months at a time. The antibiotics prescribed for some common conditions, such as acne, do not usually affect the contraceptive pill, but ask your GP if you are unsure. 

Long-term rifampicin or rifabutin

If you are going to be taking rifampicin or rifabutin for over two months, you may want to consider starting or changing to a contraception method that is not affected by these medicines. For example:

  • progestogen injection 
  • intrauterine device (IUD) 
  • intrauterine system (IUS) 

Short-term rifampicin or rifabutin

If you are taking rifampicin or rifabutin for less than two months and want to continue with your same combined contraceptive pill, you must discuss this with your doctor or specialist nurse.

You may need to use additional contraception (such as condoms) while you are taking the antibiotics and for 28 days after finishing the course. You may also need to change to a higher strength pill and take your pill in a different way from usual. You will need to continue this for 28 days after finishing the course.
 
Your GP will be able to give you further advice.

Other medicines

The pill can interact with medicines called enzyme inducers, which reduce the effectiveness of the pill.

Examples of enzyme enducers include:

  • the epilepsy drugs carbamazepine, oxcarbazepine, phenytoin, phenobarbital, primidone and topiramate
  • St John's Wort (a herbal remedy)
  • antiretroviral medicines used to treat HIV

Your GP or nurse may advise you to use an alternative or additional form of contraception while you are taking one of these medicines.

Page last reviewed: 13/07/2011

Missed pills

Missing pills or starting a pack late 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.

What to do if you miss a pill or pills

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 (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 - see below
  • you may need to start the next pack of pills without a break - see below

Emergency contraception

You may need emergency contraception if you have had unprotected sex in the previous seven days and have missed two or more pills (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

The pill is less effective when…

  • it is not taken according to the instructions
  • it does not stay in the body long enough to work, for example because of vomiting or diarrhoea
  • other medicines make it less effective

Am I protected from pregnancy during the seven-day break or when taking inactive pills?

If you have taken all your pills correctly and nothing else has happened to you to make the pill less effective (such as vomiting), you are protected from pregnancy during the seven-day break or when taking inactive pills.

Page last reviewed: 13/07/2011

There are some risks associated with using the combined contraceptive pill (the pill). However, these risks are not common. For most women, the benefits of the pill outweigh the risks.

Blood clots

The oestrogen in the pill may cause your blood to clot more readily. If a blood clot develops, it could cause a 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 should not be taken if you have two or more risk factors.

Risk factors include:

  • being over 35 years old
  • being a smoker or having quit smoking in the last year
  • being very overweight (the pill should not be taken if your BMI is over 40)
  • 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

Cancer

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 very rare form of liver cancer.

However, the pill does offer some protection against developing cancers of the endometrium (lining of the womb), ovaries and colon.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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