Birth control pill fact sheet

The pill is one of most effective non-permanent methods of birth control. Pills are nearly 100% (99.6%) effective in preventing pregnancy, if they are taken correctly. However they do not prevent sexually transmitted diseases.

Prevents pregnancy

Birth control pills contain estrogen and progesterone, the two natural female hormones. These hormones help to prevent pregnancy by:

  1. Stopping ovulation each month
  2. Changing the lining of the uterus
  3. Changing the cervical mucous


  • Periods will be regular, lighter and shorter with less cramping
  • Improvement of acne problems is common
  • The pill helps prevent cancer of the ovaries and uterus
  • Less chance of cysts on the ovaries and benign breast disease

Birth control instructions

Birth Control
  1. Start your first pack of pills on the first Sunday after your period begins. If your period begins on Sunday start your pills that day.
  2. Use a back-up method (foam, condoms, sponge) along with the pills for the first month.
  3. Take a pill every day until you finish a pack then start a new pack. Do not skip any days between packs.
  4. It is very important to take your pills every day at the same time. If you miss or take any pills late, you may spot or bleed and should use a back-up method until you start the next pack of pills.
  5. If you are late with a pill by 4 hours or more, be sure to use a back-up method until you start the next pack of pills.
  6. If you miss one pill, take it as soon as you remember it, then take today's pill at the regular time. Use a back-up method until you start the next pack of pills.
  7. If you miss two pills in a row, take two pills as soon as you remember and two pills the next day. Example: If you forget pills on Monday and Tuesday, take two pills on Wednesday and two pills on Thursday to catch up. Use a back-up method until you start the next pack of pills.
  8. If you miss three pills in a row, start using a back-up method right away. Start a new pack of pills on the next Sunday after the last pill you took. Use your back-up method until you finish the new pack of pills. If you have been sexually active before starting your new pack of pills you must wait for your next period before starting. You need to use another form of birth control for the month and for the next cycle of pills.
  9. Missed periods
    • If you have taken all pills correctly and have a very light or miss a period, keep taking your pills.
    • If you miss two periods in a row, call the clinic.
    • If you miss any pills and miss a period, call the clinic. You may need a pregnancy test.
  10. If you get sick and have diarrhea or vomiting within two hours of taking the pill, use a back-up method until you start your next pack of pills. Keep taking your pills.
  11. Anytime you see a doctor/nurse, be sure to mention you are on birth control pills especially if you may be admitted to a hospital.
  12. Certain medicine, such as antibiotics, may cause your pills to be less effective. Call the clinic to find out if you need to use a back-up method.


With any of these signs, call the clinic or family physician right away.

  1. If you miss a pill by 4 hours, use a back-up method, like condoms and spermicide, for the rest of the pill packet.
  2. When using an antibiotic, use a back-up method, like condoms and spermicide, for the rest of the pill packet.
  3. Warning signs:
    • Severe chest pain with shortness of breath
    • Worst headache of your life
    • Visual changes
    • Numbness, tingling, weakness of arms or legs
    • Severe abdominal pain
    • Severe leg pain with swelling
  4. Call the clinic if you miss more than two pills in a row.

Birth control pills do not protect you against sexually transmitted diseases. Use condoms and spermicide every time you have sex to protect yourself from getting a sexually transmitted disease including AIDS.

Adjusting to the pill

Some women may notice minor changes when first starting the pill. These changes are usually greatly improved or go away completely after the first two to three months. Possible changes may include:

  • Breast tenderness or fullness
  • Nausea - taking pills with food should help; call the clinic if vomiting is a problem.
  • Spotting (breakthrough bleeding) - does not mean there is something wrong with you or that the pill is too strong or weak for you
  • Very short and light periods - some women will have only a drop of blood or brown smear on a pad, tampon, or underwear. It is normal for some women to miss a period completely or have no bleeding (see pill instructions for missed period).
  • Weight gain/fluid retention - usually not greater than 5 pounds. A healthy diet, less intake of salty foods and regular exercise will help.
  • Acne - a few women may have an acne flare-up
  • Mood changes - usually mild and temporary

Call the clinic if these changes are severe or do not go away after the first two to three months.

Danger signs

  • Severe abdominal pain
  • Severe chest pain, shortness of breath, coughing up blood
  • Severe headache, numbness of lips, tongue, arm or leg
  • Eye problems - vision loss, blurring, flashing lights
  • Severe leg pain - redness, swelling of calf or thigh

Call your doctor's office if you develop any of the danger signs listed above.

Last reviewed: 
November 2015

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