What causes vaginal bleeding after a bowel movement and when should it be taken seriously?

Not normal: Vaginal bleeding when you are not on your menstrual cycle is not normal. If it is after a bowel movement, there could be a GI cause as well. See your doctor for evaluation.

Bleeding: You should see a doctor. Sometimes after bowell movement you can see some blood on your underwear and think is vaginal, when in reality is rectal bleeding. This is seen mostly in constipation. Either way go and get checked by a professional.