Can alcohol decrease the pill's effectiveness?

Originally Published: October 27, 2000 - Last Updated / Reviewed On: January 30, 2009
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Dear Alice,

My girlfriend recently began taking the pill. I heard from a friend that alcohol can decrease the effectiveness of this method of birth control even if she is completely responsible about it.

Dear Reader,

Luckily for women who enjoy sex, responsible drinking, and the pregnancy-protection that the pill provides, alcohol does not decrease the effectiveness of birth control pills. The chances of becoming pregnant while taking the pill are 1 out of 100 when the pill is used correctly (3 out of 100 is the stat for average users, accounting for possible missed or late pills). These rates are not changed by alcohol use. However, what drinking alcohol can change is the likelihood of missing a dose of the pill because of intoxication, and the chances of contracting a sexually transmitted infection (STI) due to an intoxication-induced impairment of judgment.

While the effectiveness of birth control pills are not impacted, biologically, by alcohol, the hormones in birth control often reduce the liver's ability to metabolize the ethanol in alcohol. This leads to higher blood alcohol concentrations in ladies on the pill and intensifies the effects of intoxication. In plain English, your girlfriend might get drunker quicker. While drunk, she could forget to take her pill at approximately the same time she does each day. If she's taking a progestin-only pill, that could be a problem. This pill's effectiveness is at risk if not taken at close to the same time each day, with a margin of error of about three hours. Estrogen and progesterone pills are not quite as time-sensitive, but women who miss a dose should take the next pill as soon as they remember, and to be extra sure they may want to use a back-up as well.

Intoxication can also cause a woman to vomit, which, if she's taken her pill recently could jeopardize its effectiveness. Finally, being drunk could inhibit a woman's judgment, and she may forget or chose not to use a condom when she normally would in order to guard against STIs. If you and your girlfriend have each been tested for STIs, and are sexually active exclusively with each other, this may not be a problem. But for women with more than one partner condoms are essential to preventing STIs. Alcohol intake has been shown to decrease the use of such protection, which is essential for guarding against STIs, including HIV.

Props to you for staying well-informed about birth control and making healthier choices regarding sexual health and reproductive health for you and your girlfriend. Knowing what's rumor and what's fact may help you enjoy the timeless combination of alcohol and sex in a responsible and safe way.