Bleeding from the rectum is common, and in most cases the cause is something treatable and not dangerous. Hemorrhoids are the single most common reason for blood in or on your stool. That said, rectal bleeding can also signal conditions ranging from a simple tear in the skin to inflammatory bowel disease or, less commonly, colorectal cancer. The color of the blood, the amount, and any symptoms that come with it all help narrow down what’s going on.
What the Color of the Blood Tells You
Bright red blood typically comes from somewhere low in the digestive tract, usually the rectum, anus, or lower colon. You might see it on the toilet paper, in the bowl, or coating the surface of your stool. Because the blood hasn’t traveled far, it stays red.
Dark maroon blood or blood mixed with jelly-like clots usually comes from higher up in the colon. Black, tarry stools point to bleeding even higher, often in the stomach or upper intestine. Blood turns dark as it passes through the digestive tract and gets broken down by digestive enzymes. If your stools look black and sticky rather than bright red, the source of bleeding is likely well above the rectum itself.
Hemorrhoids
Swollen veins in the rectum or anus are the leading cause of rectal bleeding. You’ll typically notice small amounts of bright red blood on the toilet paper or dripping into the bowl after a bowel movement. Hemorrhoids often develop from straining, sitting for long periods, or during pregnancy. About 40% of pregnant women experience rectal bleeding, and hemorrhoids are the primary reason. The bleeding is usually painless with internal hemorrhoids, though external ones can itch or ache. Most hemorrhoids improve with dietary fiber, adequate water, and over-the-counter treatments.
Anal Fissures
An anal fissure is a small tear in the lining of the anal canal, often caused by passing a hard or large stool. The hallmark is sharp pain during a bowel movement that can linger for hours afterward. You’ll also see a streak of bright red blood on the stool or toilet paper. Fissures are extremely common and usually heal on their own within a few weeks, especially if you soften your stools with fiber and stay hydrated. Chronic fissures that don’t heal may need further treatment.
Diverticular Bleeding
Diverticulosis, where small pouches form in the wall of the colon, becomes increasingly common with age. Most people with diverticula never have problems, but occasionally a blood vessel near one of these pouches ruptures. When it does, the bleeding tends to be sudden, painless, and heavy. The stool can range from bright red to dark maroon, often mixed with clots. This type of bleeding stops on its own in most people, but in roughly 9 to 19% of cases the blood loss is rapid and significant enough to require hospital care. Because it’s painless, diverticular bleeding can catch people off guard.
Colon Polyps and Colorectal Cancer
Polyps are small growths on the inner lining of the colon or rectum. Most are harmless, but some can develop into cancer over time. Both polyps and cancerous growths can bleed when stool passes over them, sometimes producing blood you can see and sometimes causing hidden blood only detectable through lab tests. A large population study of primary care patients found that among those who went to their doctor specifically for rectal bleeding, roughly 1 to 2% were eventually diagnosed with colorectal cancer. That means the vast majority of people with rectal bleeding do not have cancer, but the possibility is exactly why persistent or unexplained bleeding deserves evaluation.
The U.S. Preventive Services Task Force recommends routine colorectal cancer screening for all adults ages 45 to 75, even those without symptoms. If you’re experiencing actual bleeding, that screening recommendation doesn’t apply to you in the usual way. Symptomatic bleeding warrants its own workup regardless of your age.
Inflammatory Bowel Disease
Ulcerative colitis and Crohn’s disease can both cause rectal bleeding, though the pattern is different from hemorrhoids or fissures. With ulcerative colitis, bleeding often comes with diarrhea, and the stool may contain mucus or pus. You might feel an urgent need to go but then be unable to pass anything, a frustrating symptom called tenesmus. Belly cramps, fatigue, and unintentional weight loss are other signals. In some people, rectal bleeding or urgency is the only early sign of the disease. If you’re having bloody diarrhea that keeps coming back over weeks, inflammatory bowel disease is one of the conditions your doctor will want to rule out.
How Rectal Bleeding Gets Evaluated
Your doctor will start by asking about the character of the bleeding (color, amount, frequency), any changes in your bowel habits, and your personal and family medical history. A physical exam typically includes a visual inspection and sometimes a digital rectal exam. For bleeding that appears to come from the anal area, an anoscope, a short, lighted tube, lets the doctor look directly at the anal canal to check for hemorrhoids or fissures.
A colonoscopy is the main tool for evaluating bleeding that might come from higher up in the colon. During this procedure, a flexible camera examines the entire length of the colon and can also remove polyps or treat a bleeding site on the spot. Younger patients with straightforward hemorrhoid symptoms and no warning signs, like unexplained weight loss, anemia, or a family history of colon cancer, often don’t need a colonoscopy. For everyone else, it’s the standard next step.
Signs That Bleeding Is an Emergency
Most rectal bleeding is not an emergency, but heavy or rapid blood loss can become dangerous. If you’re bleeding from the rectum and also experience any of the following, you need emergency care:
- Dizziness or lightheadedness when you stand up
- Rapid, shallow breathing
- Fainting or confusion
- Cold, clammy, or pale skin
- Blurred vision
- Nausea
- Very low urine output
These are signs your body is losing blood faster than it can compensate. Severe dizziness on standing, combined with a heart rate that jumps by 30 beats per minute or more when you go from sitting to standing, is a particularly reliable indicator of significant blood loss. Diverticular bleeding and ulcers are among the most common causes of this kind of acute, high-volume hemorrhage.
What to Pay Attention To
A one-time streak of bright red blood after a hard bowel movement is almost always a fissure or hemorrhoid. Bleeding that recurs over several weeks, changes in your stool caliber or frequency, blood mixed into the stool rather than sitting on the surface, or any accompanying weight loss or fatigue all raise the stakes. Your age matters too: the likelihood of a serious cause increases as you get older, which is part of why screening guidelines now start at 45. Even if the bleeding seems minor, keeping track of how often it happens and what it looks like gives your doctor useful information if you decide to get it checked out.