I'm on birth control pills. What should I do if I experience diarrhea or vomiting? How or when does it affect the pill?

Use backup. If you vomit the pill, it might lose efficacy and you would be wise to use some back up contraceptive for the next two weeks. Diarrhea is not the same issue.

Related Questions

I'm on birth control pills. What should I do if I experience diarrhea or vomiting? How does it affect the pill?

Depends. If you are vomiting up the pills it can be a problem. If you lose one dose this way it is not an issue but if vomiting causes you to miss two doses then you need to use back up protection until you have been back on your pills regularly for a few weeks. Read more...