Seeing blood when you poop is usually caused by something minor, like hemorrhoids or a small tear in the skin around your anus. These two causes account for the vast majority of rectal bleeding episodes in otherwise healthy adults. But blood in the stool can also signal conditions that need medical attention, so the color of the blood, the amount, and any symptoms that come with it all matter.
What the Color of the Blood Tells You
Bright red blood typically comes from the lower part of your digestive tract, meaning the rectum or the end of the large intestine. Because the blood hasn’t traveled far, it stays red. You might see it on the toilet paper, dripping into the bowl, or coating the surface of your stool.
Dark, tarry, almost black stools point to bleeding higher up in the digestive tract, such as the stomach or small intestine. Blood that travels the full length of your gut gets broken down along the way, turning it dark and giving stools a sticky, tar-like consistency. Dark blood is generally more concerning because it suggests a source that’s harder to see and often harder to treat on your own. If your stools look black and tarry, that warrants prompt medical evaluation.
Hemorrhoids: The Most Common Cause
Hemorrhoids are swollen veins around your anus or just inside the rectum. They’re extremely common, and most don’t cause pain. What they do cause is small amounts of bright red blood, often noticed on the toilet paper or in the bowl after a bowel movement. Straining during bowel movements, sitting for long periods, pregnancy, and chronic constipation all increase the risk.
Fiber makes a real difference here. A meta-analysis in the American Journal of Gastroenterology found that people who increased their fiber intake cut their risk of hemorrhoid-related bleeding by about 50%. Studies used fiber supplements in the range of 7 to 20 grams per day. In one trial tracking patients for 18 months, those in the fiber group had recurrence rates of 15%, compared to 45% in the group that didn’t increase fiber. Keeping stools soft and easy to pass reduces the pressure on those swollen veins, which is the simplest way to prevent repeat episodes.
Anal Fissures
An anal fissure is a small tear in the lining of the anus. Unlike hemorrhoids, fissures tend to hurt, sometimes sharply, especially during a bowel movement. You’ll typically see blood when you poop or wipe. Fissures often develop after passing a particularly large or hard stool, and they’re also common in people with chronic diarrhea. Most heal on their own within a few weeks once you soften your stools with fiber and hydration.
Inflammatory Bowel Disease
If you notice blood in your stool along with ongoing diarrhea, abdominal cramping, or urgency, inflammatory bowel disease (IBD) could be the cause. The two main forms are ulcerative colitis and Crohn’s disease, and they affect the digestive tract differently.
Ulcerative colitis causes ulcers in the lining of the large intestine and rectum. Bleeding is one of its hallmark symptoms, and the blood is usually bright red because it originates in the lower gut. Some people with ulcerative colitis bleed even when they’re not passing stool, often as a slow, steady loss.
Crohn’s disease can affect any part of the digestive tract, so bleeding is less predictable. It’s most likely to cause visible blood when inflammation is located in the colon or rectum. Crohn’s bleeding tends to be less frequent than in ulcerative colitis, but it still warrants evaluation if it’s persistent or comes with weight loss, fatigue, or fever.
Diverticular Bleeding
Diverticula are small pouches that form in the wall of the colon, usually in people over 40. They’re very common and usually harmless. But a blood vessel near one of these pouches can weaken and rupture, producing what can be a surprisingly large amount of bleeding. Diverticular bleeding is typically painless, which distinguishes it from most other causes. You may feel an urge to go to the bathroom and then pass a significant volume of blood. While it often stops on its own, the volume alone can be alarming enough to warrant an emergency room visit.
Medications That Increase Bleeding Risk
Certain medications can either cause bleeding in the digestive tract or make existing bleeding worse. Aspirin and other anti-inflammatory painkillers like ibuprofen and naproxen irritate the stomach lining and reduce your blood’s ability to clot. The FDA has specifically warned that aspirin-containing antacid products can cause stomach or intestinal bleeding.
Your risk is higher if you’re combining these medications with blood thinners, steroid medications like prednisone, or multiple anti-inflammatory drugs at once. If you’re taking any of these and notice blood in your stool, it’s worth mentioning the specific medications to your doctor, since the bleeding pattern may be medication-related rather than a sign of a new condition.
When Blood in the Stool Could Signal Cancer
Colorectal cancer can cause rectal bleeding, and it’s the possibility most people are worried about when they search this question. The reassuring reality is that most rectal bleeding isn’t cancer. But there are patterns worth paying attention to.
The American Cancer Society lists these warning signs for colorectal cancer: a change in bowel habits (diarrhea, constipation, or narrower stools) lasting more than a few days, rectal bleeding, blood in the stool that looks dark brown or black, cramping or abdominal pain, unexplained weight loss, and persistent fatigue or weakness. The fatigue and weakness can come from slow, chronic blood loss that gradually lowers your red blood cell count. Sometimes that anemia shows up on a routine blood test before any visible bleeding appears.
No single symptom on this list means cancer. But if you have rectal bleeding combined with any of these other changes, especially unexplained weight loss or a lasting shift in your bowel habits, that combination deserves a thorough evaluation.
When Rectal Bleeding Is an Emergency
Most episodes of rectal bleeding are small, stop quickly, and can wait for a scheduled appointment. But certain situations call for immediate help.
Call 911 if you have significant rectal bleeding along with any signs of shock: rapid or shallow breathing, dizziness or lightheadedness when you stand, blurred vision, fainting, confusion, nausea, cold or clammy skin, or very low urine output.
Go to an emergency room if the bleeding is continuous or heavy, or if it comes with severe abdominal pain or cramping. “Heavy” generally means you’re passing clots, the toilet water is deep red, or you’re soaking through pads. These situations can indicate blood loss that needs to be addressed quickly, regardless of the underlying cause.
Making Sense of Occasional Bleeding
If you see a small amount of bright red blood on the toilet paper once in a while, particularly after straining or passing a hard stool, hemorrhoids or a fissure are the most likely explanation. Increasing your fiber intake to the range of 20 to 30 grams per day, drinking plenty of water, and avoiding prolonged straining can resolve the problem for most people.
What matters is the pattern. A single episode of minor bleeding that resolves is very different from recurring blood, changing stool habits, or bleeding that comes with pain, weight loss, or fatigue. Tracking what you notice, how often it happens, and what other symptoms come with it gives your doctor the clearest picture if you do need further evaluation, which typically starts with a physical exam and may include a colonoscopy depending on your age, symptoms, and risk factors.