Blood in your stool usually comes from somewhere along your digestive tract, and the color of the blood is the single biggest clue to where the problem is. In most cases, the cause is something minor like hemorrhoids or a small tear in the skin around the anus. But because rectal bleeding can also signal more serious conditions, it’s worth understanding what different types of bleeding look like and when to take action.
What the Color of the Blood Tells You
Your digestive tract is essentially a long tube, and blood changes appearance the longer it travels through it. Bright red blood on the toilet paper or in the bowl typically means the bleeding is coming from somewhere near the exit: the rectum, anus, or lower colon. This is the most common type people notice, and it’s the least likely to indicate something deep in the GI tract.
Dark maroon or burgundy-colored blood mixed into the stool usually points to bleeding higher up in the colon or in the small intestine. The blood has had more time to break down, which darkens it.
Black, tarry stool with a distinctive sticky texture suggests bleeding in the upper digestive tract, often the stomach or the first part of the small intestine. It takes roughly 100 to 200 mL of blood in the upper GI tract to produce this kind of stool, and the black color can persist for several days after the bleeding has actually stopped. That delay can be confusing, so don’t assume ongoing black stools always mean active bleeding.
Foods and Medications That Mimic Bleeding
Before you panic, consider what you’ve eaten or taken recently. Beets and foods with red coloring can make stool appear reddish, closely mimicking blood. On the dark end, black licorice, blueberries, iron supplements, activated charcoal, and bismuth-based medications (like Pepto-Bismol) can all turn stool black. The key difference is texture: medication-related black stool is usually firm and normal in consistency, while true upper GI bleeding produces stool that’s sticky, tarry, and has a strong, unusual smell.
The Most Common Causes
Hemorrhoids
Hemorrhoids are swollen blood vessels in or around the rectum, and they’re by far the most frequent reason people see blood after a bowel movement. The blood is typically bright red and shows up on the toilet paper or drips into the bowl. Most hemorrhoids don’t cause pain, though external ones can feel uncomfortable, especially during straining. They tend to flare up with constipation, prolonged sitting, pregnancy, or heavy lifting.
Anal Fissures
An anal fissure is a small tear in the lining of the anus, usually caused by passing a hard or large stool. Unlike hemorrhoids, fissures are more likely to hurt, sometimes sharply, during and after a bowel movement. You’ll see bright red blood when you poop or wipe. Most fissures heal on their own within a few weeks if you keep stools soft with adequate fiber and water.
Other Lower GI Causes
Diverticular disease, where small pouches form in the colon wall and occasionally bleed, is common in adults over 50. Inflammatory bowel conditions like Crohn’s disease or ulcerative colitis cause chronic inflammation that can lead to blood and mucus in the stool, typically alongside diarrhea, cramping, and fatigue. Infections from bacteria or parasites can also cause temporary bloody diarrhea. Polyps, which are small growths on the colon lining, may bleed intermittently and are important to catch early because some can become cancerous over time.
When Rectal Bleeding May Signal Cancer
Colorectal cancer can cause rectal bleeding that looks either bright red or dark maroon. One distinguishing feature: bleeding from cancer can happen at any time, not just during bowel movements, while hemorrhoid-related bleeding almost always occurs during or right after passing stool.
Blood alone isn’t enough to suspect cancer. The warning signs that should raise your concern are a combination of symptoms happening together: a persistent change in bowel habits (new diarrhea, constipation, or noticeably narrower stools), a feeling that your bowel doesn’t empty completely, unexplained weight loss, ongoing fatigue or weakness, and abdominal pain. Any single one of these alongside rectal bleeding is worth bringing to your doctor promptly.
Routine screening catches many colorectal cancers before symptoms ever appear. The U.S. Preventive Services Task Force recommends that all adults begin screening at age 45 and continue through age 75. If you have a family history of colorectal cancer or polyps, your doctor may recommend starting earlier.
How Doctors Figure Out the Cause
If you report blood in your stool, your doctor will likely start with a physical exam and questions about the color, frequency, and any accompanying symptoms. For many people, especially younger adults with obvious hemorrhoid symptoms, this is enough to reach a diagnosis.
When the source isn’t obvious, a stool test can check for hidden (occult) blood you can’t see with the naked eye. The newer version of this test, called FIT, is significantly more accurate than the older type. In studies, FIT detected about 89% of colorectal cancers compared to 59% for the older guaiac-based test. A positive stool test doesn’t mean cancer. It means blood was detected, and a colonoscopy is the next step to find out why.
A colonoscopy lets a doctor visually inspect the entire colon and rectum using a flexible camera. It’s both diagnostic and therapeutic: if polyps are found, they can be removed during the same procedure. For suspected upper GI bleeding (black, tarry stools), an upper endoscopy examines the esophagus, stomach, and upper small intestine instead.
Signs That Need Immediate Attention
Most rectal bleeding is not an emergency. A small amount of bright red blood with an otherwise normal bowel movement can usually wait for a regular doctor’s appointment, especially if you suspect hemorrhoids or a fissure.
Heavy or continuous bleeding that doesn’t stop is a different situation and warrants an emergency room visit, particularly if it’s accompanied by severe abdominal pain or cramping. Call 911 if you experience significant rectal bleeding along with any signs that your body isn’t circulating blood well: dizziness or lightheadedness when you stand up, rapid shallow breathing, confusion, blurred vision, fainting, cold or clammy skin, or very low urine output. These indicate potentially dangerous blood loss that needs immediate treatment.
Even mild rectal bleeding that keeps coming back over weeks deserves medical evaluation. Intermittent bleeding is easy to dismiss, especially when it seems to match hemorrhoid patterns, but persistent or recurring blood in your stool is your body telling you something needs a closer look.