Research question

So, let's say that someone has a nosebleed that goes on fairly heavily for a long period of time (half and hour? forty-five minutes? I'm not sure). When would they start feeling the effects of blood loss? And what would the people in the hospital do if they went to the emergency room. The nosebleed isn't brought on by any hits to the head or anything. It's not a natural nosebleed, but from, uh, supernatural causes lets say.

Anyway. I'm not sure what constitutes a long nose bleed and treatment (beyond iron).

Thanks.