Birth control methods have high rates of effectiveness if they are used consistently. Follow your health professional's instructions on what to do if you miss or skip your birth control pills. Some general guidelines are listed here.

Combination (estrogen plus progestin) birth control pills

The greatest risk for pregnancy occurs if you start taking combination (estrogen plus progestin) pills late or stop too early (that is, you don't finish the month's worth of pills). If you use a 21-pill pack, you take 3 weeks of hormone pills and go 1 week without pills. If your pills come in packs of 28, the last 7 pills usually do not have hormones.

If you miss even one hormone pill in the first week of your pack, or if you are late to start your new pack, use emergency contraception (special hormone pills). And then start taking your pills on schedule the next day. That first week of the pill pack is when there is a greater chance that your body will release an egg (ovulate) and you can become pregnant.

After missing one or more pills, be sure to follow these instructions:¹

• If you miss 1 pill during week 2 or 3 of your pack, take it as soon as you remember. Take your next pill at the regular time.
• If you miss 2 pills, take 1 of the forgotten pills every 12 hours until you have caught up, then continue taking the rest of the pill pack. Use backup contraception, like a condom or diaphragm, over the next 7 days.
• If you miss more than 2 pills and have had sex in the last 5 days, use emergency contraception. Then start taking your daily pills the next day. Use a backup method, like a condom or diaphragm, over the next 7 days. If you have had sex and decide not to use emergency contraception, skip the missed pills and complete the rest of the pill pack. Use backup contraception, like a condom or diaphragm, until your next menstrual period. Taking the rest of the pill pack does not protect you from pregnancy but will control your cycle.
• If you miss more than 2 pills and have not sex in the last 5 days, take 2 pills at once, then start taking your daily pills the next day. Use a backup method, like a condom or diaphragm, over the next 7 days.

Emergency contraception

If you had unprotected sex during the time that you missed taking pills, you can use emergency contraception to help prevent pregnancy. You can buy the emergency contraceptive Plan B (sometimes called the "morning-after pill") in most drugstores.

• If you are 18 or older, you can get Plan B from a pharmacist, without a prescription. Bring proof of your age.
• If you are younger than 18, you can get Plan B with a prescription from a doctor.

Illness

Vomiting and diarrhea can decrease the effectiveness of birth control pills. It is recommended that another method of birth control be used for 7 days after you have had the flu, even if you did not miss any pills.

Talk to your health professional if you are taking medications for epilepsy (phenytoin and barbiturates) or tuberculosis (rifampin). These medications may interfere with how well your birth control pills work.

Progestin-only pills

Progestin-only pills must be taken at the same time each day. If a pill is taken more than 3 hours late, another method of birth control should be used for the next 48 hours to prevent pregnancy. If you forget to take a pill for even one day, you must use a second method of birth control until your next period to prevent pregnancy.² You can't take extra pills as with combination pills to make up for a missed day.