Gastrointestinal bleeding can occur in the upper or lower GI tract. The most common causes of upper GI bleeding are peptic ulcer disease and esophageal/gastric varices, while hemorrhoids and diverticulosis are leading causes of lower GI bleeding. Colonoscopy is both diagnostic and therapeutic for GI bleeding and more accurate than other tests. Treatment involves fluid resuscitation, stopping ulcer-causing agents, acid suppression with PPIs, and antibiotics if H. pylori is detected to prevent ulcer recurrence.