As a general rule, an ordinary nosebleed will not cause a screening stool blood test (hemoccult or guaiac) to come back positive. However, if the nosebleed is bad enough to consider going to the emergency room... and you are swallowing a lot of it... only than will it be likely that such stool tests will come back positive for blood. To be precise, such stool tests turn positive only if there's at least 2+ teaspoons of blood leaking into the digestive system everyday (or swallowed…