Blood in your stool is surprisingly common. Population studies estimate that about 1 in 7 adults have experienced rectal bleeding, and most causes are not life-threatening. The color of the blood, where it appears, and what other symptoms come with it all point toward different explanations, ranging from a small tear near your anus to conditions that need prompt treatment.
What the Color of the Blood Tells You
The single most useful clue is color. Bright red blood typically comes from your lower digestive tract, usually the colon, rectum, or anus. Because it hasn’t traveled far, it stays red and may show up on toilet paper, on the surface of your stool, or dripping into the bowl.
Black, tarry stool is a different signal entirely. Digestive chemicals break down blood as it moves through your system, turning it dark and sticky. This appearance, called melena, usually means bleeding higher up: your stomach, the upper part of your small intestine, or occasionally your lower esophagus. Jet-black stool with a tar-like consistency should always be taken seriously, because upper GI bleeding can be harder to detect and easier to underestimate.
Maroon-colored stool falls somewhere in between and can indicate bleeding in the middle of your digestive tract.
Hemorrhoids and Anal Fissures
These two conditions are the most frequent reasons people see bright red blood after a bowel movement, and they share a lot of overlap. Both can develop from straining too hard, passing large or hard stools, or chronic constipation. Both cause red blood on the toilet paper or in the bowl.
The key difference is pain. Hemorrhoids don’t always hurt. Anal fissures, which are small tears in the lining of the anal canal, cause pain about 90% of the time. That pain tends to be sharp during a bowel movement and may come with burning, itching, or muscle spasms. Hemorrhoid discomfort, when present, is more of a constant pressure or ache. About half of people who get anal fissures develop them before age 40, and they’re especially common during pregnancy.
Both conditions usually heal on their own with softer stools, more fiber, and adequate water. If bleeding persists beyond a couple of weeks or keeps coming back, it’s worth getting checked to confirm that one of these really is the cause.
Inflammatory Bowel Disease
Ulcerative colitis and Crohn’s disease cause chronic inflammation in the digestive tract, and bloody stool is one of the hallmark symptoms. With ulcerative colitis, you’ll typically notice diarrhea mixed with blood, mucus, or pus, along with belly pain, cramping, and an urgent need to use the bathroom (sometimes without being able to go). Fatigue, weight loss, and fever are common as the disease progresses.
What separates IBD from a simple fissure or hemorrhoid is the pattern. The bleeding is persistent or recurring, it comes with other digestive symptoms, and it doesn’t resolve by changing your diet or adding fiber. Diagnosis usually involves blood tests looking for signs of infection and anemia, stool tests checking for specific inflammatory proteins, and direct visualization of the intestinal lining through a scope.
Medications That Increase Bleeding Risk
Certain drugs make your digestive tract more vulnerable to bleeding. Anti-inflammatory painkillers like ibuprofen and naproxen can damage the lining of your stomach and intestines, roughly doubling the risk of GI bleeding in some studies. Blood thinners (anticoagulants) carry an even higher risk, with research showing they can increase the odds of mid-gut bleeding by more than four times compared to people not taking them.
A surprising finding: acid-reducing medications (proton pump inhibitors), often taken to protect the stomach, may actually promote bacterial overgrowth in the small intestine that worsens NSAID-related damage further down the tract. If you take any combination of these medications and notice blood in your stool, that’s important information to bring to your doctor.
Colorectal Cancer
This is the possibility most people fear when they search this question. Colorectal cancer can cause rectal bleeding, and it’s one reason screening matters. The U.S. Preventive Services Task Force now recommends screening starting at age 45 for all adults, lowered from the previous threshold of 50. Screening is strongly recommended through age 75, and selectively offered from 76 to 85.
Blood from colorectal cancer may be visible or invisible to the naked eye. Stool-based screening tests use antibodies that detect tiny amounts of human blood, even when you can’t see it. These tests are specific to bleeding from the colon and rectum and aren’t thrown off by diet or medications. Their sensitivity for detecting cancer is moderate (around 66% in large studies), which is why repeat testing on a regular schedule improves detection over time. Colonoscopy remains the most thorough option, though it can miss flat or depressed growths that don’t look like typical polyps.
Bloody stool alone doesn’t mean cancer, especially in younger adults. But bleeding combined with unexplained weight loss, a change in bowel habits lasting more than a few weeks, or a family history of colorectal cancer raises the priority of getting screened.
Foods and Supplements That Mimic Blood
Before you panic, consider what you’ve eaten or taken recently. Beets and foods with red coloring can make stool look reddish. Black licorice, blueberries, iron supplements, activated charcoal, and bismuth-containing medications like Pepto-Bismol can all turn your stool black, mimicking the appearance of upper GI bleeding. A simple chemical test at your doctor’s office can confirm whether the discoloration is actually blood.
When Rectal Bleeding Is an Emergency
Most rectal bleeding is not an emergency, but some situations require immediate care. Heavy or continuous bleeding that doesn’t stop, or bleeding accompanied by severe abdominal pain or cramping, warrants a trip to the emergency room.
Call 911 if you’re bleeding from the rectum and experience any signs of significant blood loss: rapid or shallow breathing, dizziness when you stand up, blurred vision, fainting, confusion, nausea, cold or clammy skin, or very low urine output. These suggest your body isn’t circulating enough blood, and that needs treatment fast.
For bleeding that’s small in amount, painless, and happens once or twice, it’s reasonable to monitor it. But only about 14% of people who experience rectal bleeding actually visit a doctor about it, which means many treatable conditions go undiagnosed longer than they need to. A single episode of minor bleeding may not require urgent action, but recurring blood in your stool, even small amounts, is worth investigating.