Blood in your stool can mean anything from a minor tear in the skin around your anus to a serious condition deeper in your digestive tract. Most of the time, the cause is something common and treatable, like hemorrhoids or a small fissure. But the color, amount, and accompanying symptoms all matter in narrowing down what’s going on.
What the Color of the Blood Tells You
The color of blood in your stool is one of the most useful clues about where the bleeding is coming from. Bright red blood typically originates lower in the digestive tract, in the colon, rectum, or anus. You might see it on the toilet paper, in the bowl, or mixed into the stool itself.
Black, tarry stools point to bleeding higher up, in the stomach or upper small intestine. When blood is exposed to stomach acid and digestive enzymes during its long journey through the gut, it darkens and takes on a sticky, tar-like consistency. This type of stool often has a distinctive foul smell. If your stool looks like this, it generally warrants more urgent attention because upper GI bleeding can be harder for the body to stop on its own.
Maroon-colored stool falls somewhere in between and may indicate bleeding in the middle portion of the digestive tract, such as the lower small intestine or the right side of the colon.
Common Causes That Are Usually Not Serious
Hemorrhoids are the most well-known cause of rectal bleeding. These swollen blood vessels inside or around the anus can bleed during a bowel movement, especially if you’re straining. They don’t always hurt, which is why some people notice blood before they notice anything else.
Anal fissures, small tears in the lining of the anus, are another extremely common cause. They’re especially frequent in infants and pregnant women, and about half of people who get them do so before age 40. Fissures produce fresh red blood and, unlike hemorrhoids, are painful roughly 90% of the time. A sharp pain during bowel movements followed by burning or itching is the classic pattern. Both hemorrhoids and fissures are often triggered by straining, hard stools, or chronic constipation.
More Serious Possibilities
Diverticular bleeding happens when small pouches that form in the colon wall (very common in people over 50) rupture a blood vessel. Among people who have these pouches, 15 to 20% will experience bleeding at some point in their lifetime. The bleeding can be sudden and heavy, producing a large volume of bright red or maroon blood with little warning. It often stops on its own, but significant episodes need medical evaluation.
Inflammatory bowel conditions like ulcerative colitis and Crohn’s disease cause chronic inflammation in the digestive tract. Bloody diarrhea, abdominal cramping, and urgency are hallmarks. These conditions tend to flare and remit over time, so intermittent bloody stools paired with digestive symptoms that come and go are worth bringing up with a doctor.
Peptic ulcers, open sores in the stomach lining or upper small intestine, are a common source of black, tarry stools. These ulcers can bleed slowly, leading to anemia over time, or bleed heavily enough to require hospitalization. Vomiting blood that looks red or resembles coffee grounds is another warning sign of an ulcer that’s actively bleeding.
Colorectal cancer is the possibility that worries most people, and it’s worth knowing the broader symptom picture. A tumor in the colon or rectum can bleed, but it also tends to produce other changes: a shift in bowel habits (new diarrhea or constipation that doesn’t resolve), a persistent feeling that your bowel isn’t emptying completely, unexplained weight loss, ongoing abdominal discomfort, and fatigue. Blood in the stool from cancer is often not visible to the naked eye, which is one reason routine screening matters.
Things That Look Like Blood but Aren’t
Before assuming the worst, consider what you’ve recently eaten or taken. Beets and foods with red coloring can make stool appear reddish. On the darker end, iron supplements, black licorice, blueberries, activated charcoal, and bismuth-based medications (the active ingredient in Pepto-Bismol) can all turn stool black. These harmless color changes can easily be mistaken for bleeding.
How Bleeding Is Investigated
Your doctor will start with straightforward questions: the color and amount of blood, how often it happens, whether it’s on the surface of the stool or mixed in, and what other symptoms you’ve noticed. A physical exam of the rectal area can identify hemorrhoids or fissures quickly.
For blood that isn’t visible, stool tests can detect tiny amounts. The fecal immunochemical test (FIT) is the most commonly used screening tool. It’s more accurate than older methods, with one widely used version detecting advanced growths about 26% of the time and correctly ruling out problems in roughly 97 to 99% of cases. It’s a take-home test that requires no special diet preparation. Depending on results and your risk factors, a colonoscopy may follow, which allows direct visualization of the entire colon.
The U.S. Preventive Services Task Force recommends colorectal cancer screening for all adults starting at age 45, lowered from the previous threshold of 50. For average-risk people, a FIT test every year or a colonoscopy every 10 years are among the recommended options, with screening continuing through age 75.
Signs That Need Immediate Attention
Most rectal bleeding is not an emergency, but certain combinations of symptoms signal that your body is losing blood faster than it can compensate. Rapid or shallow breathing, dizziness or lightheadedness when you stand, blurred vision, fainting, confusion, nausea, cold or clammy skin, and very low urine output are all signs of significant blood loss. If you’re passing a large amount of blood and experiencing any of these, that’s a situation for emergency care, not a wait-and-see appointment.
Outside of emergencies, rectal bleeding that keeps recurring, changes in character, or comes with unexplained weight loss, persistent changes in bowel habits, or increasing fatigue is worth investigating sooner rather than later. Even when the cause turns out to be something minor, getting a clear answer removes the uncertainty.