Birth Control Pills (Oral Contraceptives)


What are birth control pills? 

Birth control pills (oral contraceptives) are hormones taken to prevent pregnancy and help with managing disruptive menstrual periods. The hormones (Estrogen (E) + Progestin (P)) in the pills change a woman's natural hormone levels and prevent her ovaries from releasing an egg each month. They also cause a thickening of the mucus on the cervix and change the lining of the uterus. The thickened mucus on the cervix makes it hard for sperm to enter the uterus. The most commonly used pills are combined estrogen+progesterone (E+P) pills. There is also a progesterone (P) only pill that you take every day and does not contain placebo pills, sometimes referred to as the “mini pill.”  There are two different vaginal ring products that deliver the hormones through the vagina but carry the same risk and benefits of oral contraceptives.

How are the pills used? 

The combined E+P pills usually come in a package of 28 pills.  Depending on the brand of pills your pack may have 21 E+P pills with 7 placebos, or 24 E+P pills with 4 placebos.  Menses typically occur when taking the placebo pills. They are also available in 91 day-pill packs with goal of menses every three months. You and your health care provider will decide which type is best for you.

  • Try to take your pill at the same time every day to help keep hormone levels steady.
  • Use condoms, even though you are taking birth control pills, for protection against sexually transmitted diseases
  • Bleeding can be irregular for 2-3 months after starting birth control pills. If you have bleeding between periods after that time, you may need a different pill. Call your healthcare provider.
  • 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 inactive placebo pills contain no medicine for birth control. Your period will come during the week that you are taking the last 4 or 7 pills.
  • 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. With this regimen, you may have more breakthrough or irregular bleeding.
  • Please read the full package insert when you get your prescription

How do I start my pills?

  • Sunday start: Start your pill on the Sunday that comes after your period or if you are menstruating on a Sunday.  If your period starts on a Sunday, take your first pill that night.  Sunday start method will avoid withdrawal bleed starting on a weekend if that is a priority.  If you start the pills greater than 5 days after the start of your period you will need to use back up contraception, such as condoms, for the first seven days of the pills.
  • First day start: Start your pills on the day your menses begins.  This provides contraception coverage immediately and back up birth control is not needed in the first 7 days.

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 as soon as you remember, even if it is the next day. Take the next pill on time.
  • If you miss 2 or more doses in a row, take two pills daily for two days
  • If you miss more than 2 pills the remaining pills are taken and back up birth control, such as condoms, should be used for the remainder of the cycle. If two or more pills are missed in the first week and unprotected intercourse occurs during this time, emergency contraceptive pills may be needed. 
  • If you miss a pill or take it late, you can have irregular bleeding and may become pregnant. Use an additional method of birth control, such as condoms, until your next period starts.

What are the advantages of birth control pills (BCP’s)?

  • Periods typically become regular and usually lighter. Menstrual cramps may be less severe.
  • May decrease acne and prevent ovarian cysts
  • Long-term use lowers the risk of ovarian and endometrial cancer.
  • Birth control pills may reduce symptoms of premenstrual syndrome (PMS) and pelvic pain
  • About 15% of long-term users report absence of menses on the pills. This is normal.  

What are the disadvantages?

  • BCP’s are ~92% effective in preventing pregnancy. This means that, for every 100 women who use the pills for a year, 8 women may become pregnant by the end of the year. Please refer to “How Effective is Your Contraception” under the learning center tab/contraceptive health at
  • You must remember to take a pill every day. The pills usually have minimal side effects, but sometimes women experience irregular menstrual bleeding or spotting, dizziness, nausea, breast tenderness or swelling, weight gain, headaches, amenorrhea (absence of menstrual period), less interest in sex or vaginal/vulvar pain and dryness.
  • Most side effects will resolve after 2-3 months of taking the pills. If you have symptoms beyond three months, or if the symptoms are bothersome or concerning, contact your healthcare provider.
  • Birth control pills do not protect you from sexually transmitted diseases. Latex or polyurethane condoms can protect against STD’s.
  • Birth control pills may not keep protecting you against pregnancy if you are taking the antibiotic Rifampin, medication for seizures or the herb St. John’s Wort. You may need to use an additional form of birth control while you are taking these.
  • For women who start combined E+P pills prior to age 17 have an increased risk for developing vulvadynia/vestibulodynia. They may notice increased pain with intimacy, pain in the vulva/vagina or even pain with tampon insertion.  If these symptoms arise, please notify your healthcare provider.
  • There is small risk that a blood clot could develop in your lower extremities. Age and patient weight are also risk for blood clots. The risk in young women (<25 yo and < 25 BMI) is 3 per 10,000 women years to as high as 50 per 10,000 women years over the age of 40 and >25 BMI. This means that if 10,000 women took the pill for a year, as few as 3 or as many as 50 could get a blood clot from the hormones. If a woman has a history of blood clots, she can NOT take combined E+P contraception but is safe to use Progestin only contraception.

Who should not take combined E+P birth control pills?  

  • Women who have had blood clots, certain cancers, heart attack or stroke should not use estrogen containing birth control pills
  • Women who have migraines with aura, especially in women over the age of 35 who are also overweight. This may increase the risk of stroke. Women less than 35 and normal weight may consider the pill.
  • Women who 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 a smoker.
  • High blood pressure (hypertension) is defined by systolic blood pressure of at least 130 mm Hg or diastolic blood pressure of at least 80 mm Hg. Hypertension is a major risk factor for cardiovascular disease. Estrogen containing birth control increases systolic blood pressure of 7-8 mm Hg and can cause hypertension in 2% of users. Progestin only contraception has no effect on blood pressure is preferred in women with high blood pressure. Patients typically return for a blood pressure check 2-3 months after starting birth control pills.

When to seek urgent medical attention?

  • Chest pain or shortness of breath
  • Severe headache
  • Unexplained pain, weakness, or swelling in the calf of one of your legs


Timothy A. Leach, MD, Inc.
110 Tampico, Suite 210
Walnut Creek, CA 94598
Phone: 925-935-6952
Fax: 925-935-1396

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