Birth Control Pills (Oral Contraceptives)

What are birth control pills?

Birth control pills (oral contraceptives) are a method of birth control that uses hormones to prevent pregnancy. The female hormones in the pills change a woman's natural hormone levels and prevent her ovaries from releasing an egg each month. The hormones also help prevent pregnancy in 2 other ways: They cause a thickening of the mucus on the cervix and they change the lining of the uterus. The thickened mucus on the cervix makes it hard for sperm to enter the uterus to fertilize any egg that might have escaped from the ovary. The change in the lining of the uterus helps prevent a fertilized egg from attaching to the uterus in the uncommon event that an egg did escape and was fertilized.

The most commonly used pills contain man-made forms of 2 female hormones: estrogen and progesterone. There is also a progesterone-only pill (the mini-pill), but it is not as effective for general use and there is a higher chance of bleeding between menstrual periods.

How are the pills used?

The combined pills usually come in a package of 28 pills. They are also available in 21-pill or 91-pill packs. You and your healthcare provider will decide which type of package is best for you. Your provider will probably advise you to start taking the pills on the Sunday after your period has started or on the first day of your next period, depending on your preference.

  • Try to take your pill at the same time every day. This will help you remember to take the pills. It will also help keep hormone levels steady.
  • Use a backup method of birth control (such as condoms and spermicide) until you have been taking the pills for 2 weeks.
  • Use condoms, even though you are taking birth control pills, for protection against sexually transmitted disease unless you have a long-term, single-partner relationship.
  • If you have bleeding between periods or no menstrual period for 2 or more cycles you may need a different pill. Call your healthcare provider for an appointment.
  • Any time you are seen for medical reasons, be sure to mention that you are taking birth control pills. This is particularly important if you are admitted to the hospital or having surgery.

21-day pill pack

If you are using the 21-pill pack, take 1 pill every day for 3 weeks. Stop taking the pills for 7 days and then start a new pack. Your period comes during the week that you are not taking pills.

28-day pill pack

If you are using the 28-day package, take 1 pill every day for 4 weeks and then start a new package the next day. The last 7 pills are inactive and contain no medicine for birth control, although some contain iron to help prevent anemia (low red blood cell count). They just keep you in the habit of taking a pill every day. Your period comes during the week that you are taking the last 7 pills.

91-day pill pack

If you are using the 91-day pill pack, you take 1 pill of active medicine every day for 12 weeks (84 days). Then you take 1 inactive pill every day for 1 week (7 days). You will have your period while you are taking the inactive pills. This means that you have a period just once every 3 months.

What if I forget to take a pill?

Your risk of pregnancy increases when you miss any pills.

If you forget 1 pill, take it the scheduled day as soon as you remember. If you don't remember until the next day, then take the missed day's pill along with the pill you are supposed to take for that day. Then go back to your regular schedule and take the next pill on time.

If you miss 2 or more doses in a row, see the information sheet that comes in the medicine package or ask your healthcare provider what to do. Use an additional method of birth control, such as condoms or spermicide, until your next period starts.

What are the benefits?

The benefits are:

  • Birth control pills are over 99% effective in preventing pregnancy if taken as directed. This means that, for every 100 women who use the pills exactly as instructed for a year, 1 or fewer women will become pregnant by the end of the year.
  • You do not have to interrupt lovemaking to use a birth control device or spermicide.
  • Periods become regular and usually lighter. Menstrual cramps may be less severe.
  • Long-term use lowers the risk of cancer of the ovary.
  • Birth control pills may reduce symptoms of premenstrual syndrome (PMS).

What are the disadvantages?

One disadvantage of birth control pills is that you must remember to take a pill every day.

The pills are generally considered safe, but sometimes they cause side effects in some women such as:

  • irregular menstrual bleeding or spotting for the first few months after you start birth control pills
  • dizziness
  • nausea and vomiting
  • swelling of your hands or ankles
  • pain, swelling, or tenderness in the abdomen
  • breast swelling or tenderness
  • more appetite and weight gain
  • trouble sleeping, weakness, lack of energy, fatigue, or depression
  • headaches
  • vaginal infection (usually yeast)
  • allergic reaction, rash, itching
  • amenorrhea (absence of menstrual period)
  • less interest in sex
  • changes in hair growth patterns
  • vision or contact lens problems
  • acne
  • yellowing of the skin or whites of the eyes (jaundice)

You should not smoke. Smoking increases the risk of serious side effects, such as heart attack, stroke, and blood clots. This is especially true if you are over 35 years old and smoke 15 or more cigarettes a day.

Other risks of taking birth control pills include cataracts, gallstones, and non-cancerous liver tumors.

Birth control pills do not protect you from sexually transmitted diseases such as AIDS. Latex or polyurethane condoms are the only safe way to protect against AIDS.

Some medicines can affect the way birth control pills work in your body. Birth control pills may not keep protecting you against pregnancy if you are taking certain antibiotics or medicines for seizures or fungal infections. Tell your healthcare provider about all medicines or natural remedies you are taking. You may need to use an additional form of birth control while you are taking these medicines.

Although some of these possible side effects may seem concerning, keep in mind that most women have no problems when taking birth control pills.

When should I call my healthcare provider?

Call your provider right away if you have any of the following symptoms:

  • sharp chest pain or sudden shortness of breath or are coughing up blood
  • sudden severe headache or vomiting, dizziness or fainting, or problems with vision or speech
  • sudden partial or complete loss of vision
  • yellowing of the skin or whites of the eyes (jaundice), especially with fever, tiredness, loss of appetite, dark urine, or light-colored bowel movements
  • a new skin rash
  • unexplained pain, weakness, or numbness in the calf of one of your legs
  • severe pain, swelling, or tenderness in the abdomen

Call during office hours if you have any of the following:

  • problems with your menstrual periods, such as bleeding between periods, prolonged periods, or 2 missed periods, or you think you are pregnant
  • more headaches than you used to have
  • severe mood changes
  • vaginal discharge with itching
Developed by David W. Kaplan, MD, and RelayHealth.
Published by RelayHealth.
Last modified: 2009-02-12
Last reviewed: 2008-10-28
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
© 2009 RelayHealth and/or its affiliates. All Rights Reserved.