Blood in your stool is surprisingly common, and in most cases it comes from a benign source like hemorrhoids or a small tear in the skin around your anus. That said, the color, amount, and accompanying symptoms all matter because they point to very different causes, some minor and some that need prompt medical attention.
What the Color of the Blood Tells You
The single most useful clue is color. Bright red blood typically comes from the lower part of your digestive tract, usually the rectum or colon. You might see it on the toilet paper, dripping into the bowl, or streaked on the surface of your stool. Because the blood hasn’t traveled far, it stays red.
Black, tarry stool is a different situation. When bleeding starts higher up, in the stomach or upper small intestine, digestive enzymes break down the blood’s proteins during the long trip through your gut. By the time it exits, the blood has turned dark and sticky. This type of stool often has a distinctly foul smell that’s different from a normal bowel movement. If you’re seeing black, tar-like stool, the cause is almost always in the upper digestive tract and warrants a call to your doctor right away.
Maroon-colored stool falls somewhere in between and can signal bleeding from the middle portions of the intestine, such as the small bowel or the right side of the colon.
Hemorrhoids and Anal Fissures
These two conditions are the most frequent explanations for bright red blood, especially in otherwise healthy adults. They look similar on toilet paper but feel quite different.
Hemorrhoids are swollen veins inside or just outside the anus. Internal hemorrhoids often bleed without causing any pain at all. You notice bright red blood on the paper or in the bowl, but the bowel movement itself feels normal. External hemorrhoids can itch or feel uncomfortable, and you may notice a tender lump near the opening.
Anal fissures are small tears in the skin lining the anus, usually caused by passing a hard or large stool. The hallmark is a sharp, stinging pain during and sometimes after a bowel movement, along with a streak of blood. If pooping hurts and you see blood, a fissure is a likely culprit. Most fissures heal on their own within a few weeks with adequate fiber, water, and warm baths.
Colon Polyps and Diverticulosis
Colon polyps are small growths on the inner lining of the colon. Most are harmless, but some can slowly develop into colorectal cancer over years. Polyps don’t always cause noticeable bleeding. When they do, the blood may be mixed into the stool rather than sitting on the surface, or it may be invisible to the naked eye and only detectable through a lab test.
Diverticulosis, where small pouches form in the wall of the colon, is extremely common after age 40. These pouches rarely cause trouble, but when a blood vessel near one of them breaks, the result can be a sudden, painless gush of maroon or bright red blood. Diverticular bleeding often stops on its own but can be heavy enough to need medical evaluation.
Inflammatory Bowel Disease
If blood in your stool comes with persistent diarrhea, cramping, urgency, or unintended weight loss, inflammatory bowel disease (IBD) is a possibility worth investigating. The two main forms, ulcerative colitis and Crohn’s disease, affect the gut differently.
Ulcerative colitis tends to cause bloody diarrhea, lower abdominal cramps, and a frequent, urgent need to get to a bathroom. You may also feel like you still need to go right after finishing. Because this condition starts in the rectum and spreads upward through the colon, bleeding is a central symptom.
Crohn’s disease more often causes belly pain with nonbloody diarrhea and weight loss, particularly when the small intestine is involved. It can, however, cause problems around the anus, including painful fissures and abnormal tunnels in the tissue called fistulas, which may produce drainage or bleeding of their own.
Upper GI Bleeding and Black Stools
Black, tarry stools usually trace back to the stomach or the first section of the small intestine. The most common culprit is a peptic ulcer, an open sore in the stomach lining or the lining of the upper small intestine. Ulcers can develop from a bacterial infection or from regular use of certain pain relievers.
NSAIDs like ibuprofen and naproxen are the most common drug-related cause of stomach and intestinal injury. They interfere with the protective lining of your gut, and regular use raises the risk of serious gastrointestinal complications by 2.5 to 5 times. Even low-dose aspirin carries an increased risk of upper GI bleeding. If you take these medications routinely and notice dark stools, that connection is worth discussing with your doctor.
Other upper GI causes include severe inflammation of the stomach lining, swollen veins in the esophagus (often related to liver disease), and tears in the esophagus from violent vomiting. Upper GI cancers affecting the stomach, esophagus, or pancreas can also produce black stool, though these are far less common than ulcers.
Foods and Supplements That Mimic Blood
Before you panic, consider what you’ve eaten recently. Beets, red gelatin, tomato soup, and red food dye can all turn stool reddish. Iron supplements, bismuth (the active ingredient in some stomach remedies), and black licorice can make stool look black without any bleeding at all. If you recently consumed any of these and feel fine otherwise, the color change is likely harmless.
When Blood in Stool Needs Urgent Attention
A small amount of bright red blood after straining, with no other symptoms, is usually not an emergency. But certain combinations of symptoms signal that your body is losing too much blood or that something more serious is happening. Get emergency help if you notice rectal bleeding alongside any of the following:
- Rapid, shallow breathing
- Dizziness or lightheadedness when you stand up
- Blurred vision or fainting
- Confusion or nausea
- Cold, clammy, or pale skin
You should also head to an emergency room if the bleeding is continuous or heavy, or if it comes with severe abdominal pain or cramping. These can be signs of significant blood loss that needs immediate treatment.
How Doctors Figure Out the Cause
If you’re already experiencing symptoms like bleeding, changes in bowel habits, or abdominal pain, doctors skip the basic screening tests and move to diagnostic procedures. A colonoscopy is the most thorough option: it lets a doctor view the entire colon and rectum, spot abnormal tissue like polyps, and take small tissue samples during the same exam. For suspected upper GI bleeding, a similar scope is passed down through the mouth to examine the esophagus, stomach, and upper intestine.
Even without symptoms, routine colorectal cancer screening is now recommended starting at age 45 for people at average risk. If you have a higher risk due to family history or other factors, screening may start earlier. The U.S. Preventive Services Task Force gives its strongest recommendation for screening between ages 50 and 75, with a newer recommendation extending screening to adults aged 45 to 49. For people 76 to 85, the decision is more individual. Blood in your stool at any age is a reasonable reason to talk to your doctor about whether a colonoscopy makes sense sooner rather than later.