Avoidance of alcohol, aspirin, and NSAIDs can prevent cases due to these causes. Many cases cannot be prevented.
Heavy, rapid bleeding can result in shock or death. Most long-term effects are related to the cause of GI bleeding. For example, hemorrhoids may be painful, but rarely cause serious long-term effects. Cancer can cause death.
GI bleeding is not contagious. In cases due to infections, the infection is sometimes contagious.