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How Effective Are Combination Birth Control Pills?

When used correctly, combination birth control pills are 99% effective at preventing pregnancy. Correct usage of birth control pills includes taking the pill every day at the same time and avoiding certain medications that can interact with the hormones in the pill. If you experience an illness that causes vomiting and/or diarrhea for more than 48 hours, these symptoms can reduce your combination birth control pill’s efficacy.

Medications and supplements that impact the pill’s effectiveness include:

  • Rifampin (antibiotic).
  • Certain medications used to prevent seizures.
  • Certain medications used to treat HIV.
  • Griseofulvin (antifungal).
  • St. John’s Wort (herb).

Starting combination birth control pills

When you start taking combination birth control pills, the timing can impact how quickly they become effective at preventing pregnancy. If you start the pill within five days of the first day of your period, you’re protected from pregnancy immediately. If you start taking combination pills at any other time during your cycle, they won’t become effective for seven days, so make sure to use a backup birth control method during that time.

Many of the most commonly prescribed birth control pills are combination pills, meaning they use two hormones to prevent pregnancy. These hormones are progestin and estrogen, which mimic your body’s naturally occurring hormones to prevent ovulation and thicken the cervical mucus to make it more difficult for sperm to meet an egg. Some of these birth control pills include:

Benefits of combination birth control pills

Combination birth control pills can also help reduce hormonal acne, reduce the severity of your periods, regulate your periods, relieve PMS symptoms such as menstrual cramps, and reduce the risk of certain types of cancers and cysts. You can use combination birth control pills to safely skip your period, as well.

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