How does the birth control pill work?
The hormones in birth control pills prevent pregnancy by blocking conception, when sperm fertilizes an egg. They also cause changes in your uterus so that it can’t support a pregnancy while you’re on the pill.
Birth control pills:
- Stop or reduce ovulation (the release of an egg from an ovary).
- Thicken cervical mucus, creating a barrier that prevents sperm from entering your uterus and eventually reaching the egg.
- Thin the lining of your uterus so that a fertilized egg can’t attach and grow there.
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When should I take birth control pills?
Take them exactly as prescribed. The pill comes in different dosing packets — including 21-day pill packs, 91-day pill packs or even 365 days of pills. Not all pills in a packet are the same. When you take some of them depends on which kind you’re using. You need to take the right pill at the right time.
Follow the instructions on the packaging, or ask your provider or pharmacist if you have questions before you start.
Combination pills
Most packets contain “active” and “inactive” pills. Active pills contain hormones. Inactive pills, sometimes called placebo pills, don’t have hormones. The inactive, hormone-free pills may be helpful reminders so that you don’t get out of the habit of taking the pill. You can also set reminders, such as an alarm, or use apps that send reminders.
Traditional dose packs
- 28-day packs: Take active pills for 21 days and inactive pills for seven days. You’ll bleed on the inactive week. (The bleeding isn’t a period. Instead, it’s your body’s response to not being on the hormones.)
- 21-day packs: Take active pills for 21 days and no pills for seven days. You’ll bleed the week you’re not taking pills. (Set reminders so you don’t forget to start a new pack on day 29.)
Extended or continuous dose packs
- 91-day packs: Take active pills for 12 weeks (three months) and inactive pills for seven days. You’ll bleed on the inactive week. (You’ll only bleed four weeks every year.)
- 365-day packs: Take active pills every day. You may have some breakthrough bleeding or no bleeding at all. Amethyst™ is the only birth control pill available as a 365-day pack.
Progestin-only pills (minipills)
Progestin-only pills contain 28 active pills that you have to take at the same time every day (within a three-hour window) to prevent pregnancy. For example, taking a pill at 7 a.m. Monday and 10:30 a.m. Tuesday (3 and a half hours) puts you at risk of pregnancy if you’re sexually active.
A newer form of the minipill called Slynd® is the exception. You take 24 active pills and then four inactive pills.
How soon does the pill work?
The pill can take up to a week to start preventing pregnancy. You’ll need to use another form of birth control during the first seven days you’re taking the pill if you’re sexually active.
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What should I do if I miss a pill?
Take the missed pill as soon as you remember, and continue taking your usual dose as planned. Use a backup form of birth control until you’ve taken seven days of active pills. It’s helpful to keep package inserts handy. Most give specific instructions on what to do if you miss a pill.
Talk to a healthcare provider if you miss several days of the pill. Your provider can discuss pregnancy tests and emergency contraception options.
Should I avoid certain medications while taking the pill?
Always check with a healthcare provider before starting new medications or herbal supplements. Certain drugs can make the pill less effective, increasing your chances of pregnancy. These include:
- Antiseizure medications.
- Herbal supplements, such as St. John’s wort.
- Medications used to treat HIV.
Can I take the pill while breastfeeding?
Your healthcare provider may recommend taking the progestin-only pill if you’re breastfeeding (chestfeeding). The combination birth control pill contains estrogen, which can decrease milk production.
However, you may switch to an estrogen-containing combination pill once your milk fully comes in.
Ask your healthcare provider which option is best for you.
