IF bleeding cannot be stopped or keeps reappearing. IF bleeding is rapid or if blood loss is large. IF you feel weak or faint, presumably from blood loss. IF bleeding begins by going down the back of the throat rather than the front of the nose.
Physicians classify nosebleeds into two different types.
Obviously, if the patient is lying down, even the anterior nosebleeds seem to flow in both directions, especially if the patient is coughing or blowing his nose. Nevertheless, it is important to try to make the distinction since posterior nosebleeds are often more severe and almost always require the physician's care. Posterior nosebleeds are more likely to occur in older people, persons with high blood pressure, and in cases of injury to the nose or face. Nosebleeds in children are almost always of the anterior type. Anterior nosebleeds are common in dry climates or during the winter months when the dry air parches the nasal membranes so that they crust, crack, and bleed.