There are certain diseases such as flu, diarrhea and gastritis which people believe that can affect the potency of birth control pill but there is very few data which can support this concept. Even antibiotics can reduce the efficiency of birth control pills. Suppose you have taken birth control pill and underwent vomiting within the two hours of consuming it, then it is necessary that you must take another replacement pill. You must also consult your health care provider for any kind of special instructions you need. If more than two hours has passes out after you have taken birth control pill, then it is unlikely that vomiting will affect the potency of birth control pill and you need not take any a replacement pill.

There is possibility that diarrhea may affect the potency of the birth control pill but it totally depends on how quickly the stuffs in your body are moving out due to diarrhea. If your birth control pill passes out from your body without getting absorbed in the body, then there you are at an increased risk of getting pregnant. So it is extremely important that you must make for replacement birth control pill to avoid the chance of getting pregnant.