Blood in Stool: What It Means and When to Worry

Seeing blood in your stool is understandably concerning. While the most common causes are benign (hemorrhoids and anal fissures), rectal bleeding always warrants evaluation to rule out more serious conditions. What the Color Tells You Bright red blood on toilet paper or in the bowl typically comes from the lower digestive tract — rectum or anus. Hemorrhoids and anal fissures are the most likely sources. Dark red or maroon blood mixed in with stool suggests bleeding from the colon, possibly from diverticulosis, inflammatory bowel disease, or polyps. Black, tarry stools (melena) indicate bleeding from the upper digestive tract — stomach or duodenum — where blood has been partially digested. This can signal peptic ulcers or gastritis. Common Causes Hemorrhoids are swollen blood vessels in the rectum that bleed with straining. They are the most common cause of rectal bleeding and affect up to 75% of adults at some point. Anal fissures are small tears in the anal lining, usually caused by hard stools. They produce sharp pain during bowel movements with bright red bleeding. Diverticular disease causes painless, sometimes significant, bright red bleeding when small pouches in the colon wall bleed. Inflammatory bowel disease (Crohn's disease and ulcerative colitis) causes chronic bloody diarrhea with mucus, cramping, and urgency. Colorectal polyps may bleed intermittently and are important to detect because some can become cancerous over time. Red Flags — Seek Immediate Care Dizziness or lightheadedness with bleeding, large amounts of blood, black tarry stools, bleeding accompanied by severe abdominal pain, or rectal bleeding in anyone over 45 who has not had a colonoscopy.