3 Things that Can Impact Pill Effectiveness

By Maryam

With perfect use, contraceptive pills can be up to 99% effective in preventing pregnancy. Typical use (taking the pill incorrectly or inconsistently – missing a pill or taking pills late) usually brings it’s effectiveness down to 91%. Here are three things that alter your pill’s effectiveness.

Throwing up

Whether you are sick or just drank too much alcohol, if you throw up within 2 hours of taking your pill it’s considered a missed pill. If this is the case, your body’s absorption of the pill could’ve been affected which means you should follow the directions for a missed pill on your pack and use a backup contraceptive method.


The good news is that not all antibiotics interfere with the pill’s effectiveness–not the most common ones at least. But certain antibiotics can decrease estrogen levels in the body.

Along with some antibiotics, various medications and herbal supplements including the commonly used St. John’s Wort can also impact your pill. Just to be safe, you should use backup methods during the time you’re on antibiotics and even for 5-7 days after you finish antibiotics. The best bet is always to ask your doctor.


The pill’s 99 % effectiveness comes with taking it on time, everyday. For progestin-only pills, compared to combination pills, the window for on-time use is even smaller at about 3 hours. With most pills, you can double up the next day if you missed a day, but make sure to check with your doctor because not all pills are the same. There are many apps to help remind you when to take your pill if setting an alarm isn’t effective enough. The pill takes a lot of self-discipline and if you can’t seem to get on track to remember it everyday, consider other methods that don’t require daily attention like the ring, patch, implant, shot, or IUD.

Have more questions about the pill? We’ve got you covered. Head to https://hi.nurx.co/category/birth-control-101/ to read our Medical Director’s answers to all things birth control.