How do oral contraceptives work

Most birth control pills are "combination pills" containing a mix of the hormones estrogen and progesterone to prevent ovulation the release of an egg during the monthly cycle. A woman cannot get pregnant if she doesn't ovulate because there is no egg to be fertilized.

The Pill also works by thickening the mucus around the cervix, which makes it difficult for sperm to enter the uterus and reach any eggs that may have been released. The hormones in the Pill can also sometimes affect the lining of the uterus, making it difficult for an egg to attach to the wall of the uterus.

Most combination pills come in either a day pack or a day pack. One hormone pill is taken each day at about the same time for 21 days. Depending on your pack, you will either stop taking birth control pills for 7 days as in the day pack or you will take a pill that contains no hormones for 7 days the day pack.

A woman has her period when she stops taking the pills that contain hormones. Some women prefer the day pack because it helps them stay in the habit of taking a pill every day. There is also a type of combination pill that decreases the frequency of a woman's period by supplying a hormone pill for 12 weeks and then inactive pills for 7 days. This decreases the number of periods to one every 3 months instead of one every month. Another kind of pill that may change the number of monthly periods is the low-dose progesterone pill, sometimes called the mini-pill.

This type of birth control pill differs from the other pills in that it only contains one type of hormone — progesterone — rather than a combination of estrogen and progesterone. It works by changing the cervical mucus and the lining of the uterus, and sometimes by affecting ovulation as well. The mini-pill may be slightly less effective at preventing pregnancy than combination pills. The mini-pill is taken every day without a break.

A girl who is taking it might have no period at all or she may have irregular periods. For the minipill to work, it must be taken at the same time every day, without missing any doses. Any type of birth control pill works best when it is taken every single day at the same time of day, regardless of whether a girl is going to have sex. This is especially important with progesterone-only pills. For the first 7 days of taking the Pill, a girl should use an additional form of contraception, such as condoms, to prevent pregnancy.

After 7 days, the Pill should work alone to prevent pregnancy. This timing can vary based on the type of Pill and when you start taking it — so be sure to talk about it with your doctor.

Also, it's important to continue using condoms to protect against sexually transmitted diseases STDs. Contraception — the combined pill. Actions for this page Listen Print. Summary Read the full fact sheet. On this page. What is the pill? How effective is the pill? How do I use the pill? How does the pill work? Where can I get the pill? What is good about the pill? Are there any side effects from taking the pill? Can the pill cause any serious health problems?

When is the pill not a good option? What if I miss a pill? What else should I know about the pill? Where to get help. What stops the pill from working? The pill may not work if: you miss a pill or it is taken more than 24 hours late you vomit within three hours of taking it you have very severe diarrhoea you are taking some medications or natural remedies.

Check with your doctor, nurse or pharmacist. You use the pill by swallowing one pill around the same time every day. The pill works by stopping the ovaries from releasing an egg each month. The pill can: be used to skip your period make your periods become lighter, more regular, and less painful improve acne reduce your chance of getting cancer of the uterus womb , ovaries and bowel help with symptoms of polycystic ovary syndrome PCOS and endometriosis.

Once you stop taking the pill your fertility quickly returns to normal. Possible side effects for a small number of people who take the pill can include: irregular vaginal bleeding nausea sore or tender breasts headaches bloating changes to your skin mood changes. These side effects often settle with time. The pill has not been shown to cause weight gain.

The pill may not be a good option for you if you: find remembering to take a daily tablet difficult have certain types of migraine or headache are very overweight have a close family member who has had a deep vein thrombosis are taking certain types of medication which might stop the pill from working check with your doctor, nurse or pharmacist have had some health conditions such as high blood pressure, heart or liver disease check with your doctor, nurse or pharmacist are over 35 years and smoke have been treated for breast cancer are unable to move around for a long time for example, because of surgery or disability.

If you miss a pill: Take the missed pill as soon as you notice this may mean taking two pills on the same day. Continue to take your pills as normal. Use condoms for the next seven days. If you have had sex without a condom in the seven days before missing a pill, you may need emergency contraception or you may need to skip your next sugar pills and start a new pill pack in the hormone section.

This depends on where you are up to in the pill packet check with your doctor, nurse or pharmacist. You can stop the pill at any time and your fertility will quickly return. Article Information. How Do Oral Contraceptives Work?

Who Can Take Oral Contraceptives? How Are Oral Contraceptives Taken? Side Effects. Other Considerations. The information and recommendations appearing on this page are appropriate in most instances, but they are not a substitute for medical diagnosis.

For specific information concerning your personal medical condition, JAMA suggests that you consult your physician. This page may be photocopied noncommercially by physicians and other health care professionals to share with patients. Back to top Article Information. Spanish Patient Page: Anticonceptivos orales. Access your subscriptions. Access through your institution. Add or change institution. Free access to newly published articles. Purchase access.

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