Blood in your stool is common, but it’s not normal. Something is causing it, even if that something turns out to be minor. The reassuring news: over 96% of people who see a doctor for rectal bleeding do not have cancer. Most cases trace back to everyday issues like hemorrhoids or small tears in the skin around the anus. Still, visible blood is always worth paying attention to because the color, amount, and accompanying symptoms tell you a lot about what’s going on.
What the Color of Blood Tells You
The color of blood in or on your stool is a rough map of where the bleeding is happening in your digestive tract. Bright red blood usually means the source is low, in the colon, rectum, or anus. This is the most common type people notice on toilet paper or in the bowl, and it’s frequently tied to hemorrhoids or fissures.
Dark red or maroon blood points to bleeding higher up, in the upper colon or small intestine. Black, tarry stools (sometimes described as looking like coffee grounds) often signal bleeding in the stomach, such as from an ulcer. Black stool from stomach bleeding has a distinct sticky texture and strong odor that’s hard to miss.
Before you panic over dark or red-tinged stool, check what you’ve eaten or taken recently. Beets and foods with red coloring can make stool appear reddish. Iron supplements, bismuth-based antacids like Pepto-Bismol, activated charcoal, black licorice, and blueberries can all turn stool black. If you’ve consumed any of these in the last day or two, that may be your answer.
The Most Common Causes
Hemorrhoids are the leading culprit. These are swollen veins around the anus, and they’re extremely common, especially during pregnancy, after straining during bowel movements, or from sitting for long periods. Most hemorrhoids don’t actually cause pain. You might notice bright red blood on the toilet paper, itching, or a small lump near the anus. The bleeding typically stops on its own and comes back intermittently.
Anal fissures are the other frequent cause. These are small tears in the skin of the anus, usually from passing hard or large stools. Unlike hemorrhoids, fissures tend to hurt, sometimes sharply, during and after a bowel movement. You may also feel a burning or itching sensation that lingers. The blood is bright red and usually shows up on the paper or on the surface of the stool rather than mixed in.
Both hemorrhoids and fissures typically improve with increased fiber, adequate water, and avoiding straining. Most episodes resolve within a few days to a couple of weeks without any procedure.
Less Common but Serious Causes
Inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis, causes chronic inflammation in the digestive tract that can lead to bloody stools. The blood is often mixed into the stool rather than just on the surface, and it tends to come with other persistent symptoms: cramping, diarrhea, fatigue, and unintentional weight loss. IBD is a long-term condition that requires ongoing management, and having it raises the risk of colon cancer over time.
Colorectal polyps, which are small growths on the lining of the colon, can bleed without causing any other symptoms. Most polyps are harmless, but some can develop into cancer. In one large primary care study, about 12% of patients who underwent a scope exam for rectal bleeding had polyps. Colorectal cancer itself was found in 3.4% of patients over age 34 who saw their doctor for bleeding.
The challenge is that the symptoms of early colorectal cancer overlap heavily with more benign conditions: blood in stool, changes in how often you go, stools that are narrower than usual, bloating, and alternating diarrhea and constipation. You can’t reliably tell the difference based on symptoms alone, which is why persistent or unexplained bleeding warrants investigation.
Signs That Need Prompt Attention
Most rectal bleeding doesn’t require a trip to the emergency room, but certain combinations of symptoms do. Heavy bleeding that doesn’t stop, blood that fills the toilet bowl, or bleeding accompanied by dizziness, lightheadedness, or feeling faint suggests significant blood loss. Severe abdominal pain alongside bloody stool could indicate a perforated ulcer or another acute problem.
Outside of emergencies, you should get evaluated if bleeding persists for more than a week or two, if it keeps coming back, or if it’s accompanied by unexplained weight loss, persistent changes in your bowel habits, or fever. These patterns don’t necessarily mean something serious is wrong, but they do mean something beyond a simple hemorrhoid needs to be ruled out.
How Doctors Figure Out the Cause
If you’re already experiencing symptoms like bleeding, changes in bowel habits, or abdominal pain, your doctor won’t start with a routine screening test. Screening tools like the fecal immunochemical test (FIT), which detects hidden blood in a stool sample, are designed for people without symptoms. They’re useful for catching problems early in healthy people but aren’t the right tool when you already have a visible issue.
For active symptoms, doctors typically move toward a direct look at the colon, usually with a colonoscopy or a flexible sigmoidoscopy. These allow them to see the source of bleeding, identify polyps or inflammation, and take tissue samples if needed. The preparation (bowel cleansing the day before) is the most unpleasant part for most people. The procedure itself is done under sedation and usually takes 30 to 60 minutes.
Screening If You Have No Symptoms
Even without visible blood, the CDC and the U.S. Preventive Services Task Force recommend that most adults begin colorectal cancer screening at age 45 and continue through age 75. If you have risk factors like a family history of colon cancer or a personal history of IBD, screening may start earlier.
For average-risk people, at-home stool tests like FIT are one option. These check for tiny amounts of blood invisible to the eye, and they’re repeated annually. They’re convenient since you collect the sample at home with no prep required. The trade-off is that they’re less sensitive than colonoscopy at catching precancerous polyps, and an abnormal result means you’ll need a colonoscopy anyway as a follow-up. A colonoscopy, while more involved, only needs to be repeated every 10 years if results are normal.
What to Track Before Your Appointment
If you decide to see a doctor about blood in your stool, a few details will help them narrow things down quickly. Note the color of the blood (bright red, dark red, or black), whether it’s on the surface of the stool, mixed in, or only on the toilet paper. Pay attention to how often it happens and whether it coincides with hard stools or straining. Track any accompanying symptoms: pain during bowel movements, changes in frequency, cramping, weight changes, or fatigue. A clear picture of what’s been happening over the past few weeks gives your doctor a much better starting point than a vague description of “some blood.”