Because both anterior and posterior nasal bleeding may result in considerable loss of blood, the physician must first assess and correct any significant hemodynamic compromise. Careful evaluation and observation is advised for elderly or debilitated patients with significant loss of blood, particularly those living alone, or patients with complicating coagulopathies (including medication induced) and cardiovascular disorders.

The majority of nosebleeds are anterior bleeds (90%) caused by minor trauma (e.g., scratching) or desiccation in the area of Kiesselbach plexus (anterior nasal septum). Other causes include rhinitis with vigorous nose blowing, cocaine sniffing, hypertension, atherosclerosis, coagulopathies, tumors, foreign bodies, and atmospheric pressure changes. There are also uncommon causes such as the Osler-Weber-Rendu syndrome or hemorrhagic telangiectasia. Nasal fractures also cause epistaxis.

Anterior nosebleeds tend to bleed predominately from one nostril. Posterior sources tend to bleed from both nares and down the back of the throat. Patients on aspirin, NSAIDs, antiplatelet agents, and warfarin tend to require more aggressive therapy. In children, a history or family history of bleeding disorders should be sought.

The relationship between hypertension and epistaxis is unclear. There is no causal evidence between anterior epistaxis and hypertension. There may be a relationship between posterior epistaxis and elevated blood pressures. Most authorities recommend treatment of the epistaxis including adequate anesthesia of the nasal cavity and anxiolytics before treating hypertension acutely. Control of bleeding often spontaneously improves blood pressure.