My daughter which is a 12 year old, has been pooping blood. what's wrong with her. emergency room? she hasn't had her period.

Maybe: If it is a lot of blood then yes. If not then see her primary doc tomorrow. The is typically infection, Crohn's disease or colitis. Constipation can do this from a year in the anus or from a hemorrhoid. This is not an emergency. If there is a lot of bloody diarrhea I would go to the ER. Of streaks of blood wait till morning

It could be from: something simple like anal fissures from constipation, but call your pediatrician's after-hours line, give a detailed history of duration, amount, frequency, color, & systemic symptoms & ask if you should take her to a specific hospital's pediatric ER.She may need to see a pediatric gastroenterologist, depending on the history. Or, take her to a hospital pediatric ER & ask them to notify her Dr.