Blood in stool doesn’t always look like blood. It can show up as bright red streaks on toilet paper, a dark maroon color mixed into the stool, or a black, tar-like consistency that you might not immediately connect to bleeding at all. The appearance depends on where in your digestive tract the bleeding originates and how far the blood has traveled before leaving your body.
What Bloody Stool Actually Looks Like
There are two main types of bloody stool, and they look very different from each other.
Bright red blood, called hematochezia, typically comes from the lower digestive tract: the colon, rectum, or anus. You might see it coating the surface of your stool, dripping into the toilet bowl, or showing up on toilet paper after wiping. It looks unmistakably like fresh blood. This is the more common type people notice, and it often comes from relatively minor issues like hemorrhoids or small tears near the anus.
Black, tarry stool, called melena, signals bleeding higher up in the digestive tract, such as the stomach or upper intestine. It looks black because the blood has been broken down by digestive enzymes as it travels through the entire length of your gut. The texture is sticky and tar-like, and it often has a distinctly foul smell that’s different from normal stool. Because it doesn’t look red, many people don’t realize they’re looking at blood at all.
A third possibility falls between these two: dark maroon or burgundy-colored stool. This generally means moderate bleeding somewhere in the middle of the digestive tract, where the blood has been partially digested but hasn’t traveled far enough to turn fully black.
Foods and Medications That Mimic Blood
Before assuming the worst, consider what you’ve eaten or taken recently. Several common substances can make stool look bloody when it isn’t. Beets and foods with red coloring can turn stool reddish, sometimes convincingly enough to cause alarm. On the dark end, iron supplements, black licorice, blueberries, activated charcoal, and bismuth-containing medications like Pepto-Bismol can all produce black stools that look similar to melena.
The key difference is texture and smell. True melena is sticky and tar-like with an unusually strong odor. Stool that’s simply darkened by iron pills or bismuth tends to be a more uniform dark color without that sticky, tarry quality. If you recently ate beets or took Pepto-Bismol and your stool looks unusual, wait a day or two after stopping and see if it returns to normal.
Blood You Can’t See at All
Sometimes bleeding in the digestive tract is so minor that you can’t detect it visually. This is called occult (hidden) blood, and it’s one reason colorectal cancer screening exists. Blood vessels in larger polyps or early cancers are fragile and bleed small amounts when stool passes by, but rarely enough to change how the stool looks to the naked eye.
Two types of at-home stool tests can detect this hidden blood. A fecal immunochemical test (FIT) uses antibodies to detect blood specifically from the lower intestines, and it doesn’t require any dietary changes beforehand. A guaiac-based fecal occult blood test (gFOBT) uses a chemical reaction to detect blood from anywhere in the digestive tract, but certain foods and medications can throw off the results. You may need to avoid red meat, vitamin C above 250 mg daily, and anti-inflammatory drugs like ibuprofen for a few days before taking it.
Both tests are done at home with a small stool sample. Neither is perfect. They can miss polyps and some cancers, and they can also produce false positives. A positive result doesn’t mean cancer; it means blood was detected and a colonoscopy is needed to find the source. The U.S. Preventive Services Task Force recommends that average-risk adults begin colorectal cancer screening at age 45, with options including annual FIT testing or colonoscopy every 10 years.
Common Causes of Visible Blood
The most frequent causes of bright red blood in stool are not serious. Hemorrhoids, which are swollen veins in the rectum or anus, are the most common culprit. The blood is usually bright red, appears on the surface of stool or on toilet paper, and may be accompanied by itching or discomfort. Anal fissures, small tears in the lining of the anal canal, produce similar-looking bleeding but tend to cause sharper pain during bowel movements. Both are often triggered by constipation or straining with hard stools.
Less common but more serious causes include inflammatory bowel disease, infections, diverticular disease, and colorectal polyps or cancer. These conditions often come with additional symptoms like persistent changes in bowel habits, abdominal pain, unexplained weight loss, or ongoing fatigue.
Signs That Require Emergency Care
Most rectal bleeding is not an emergency, but certain situations require immediate medical attention. Go to the emergency room if you’re passing a large volume of blood, if you feel lightheaded or dizzy, if you have severe abdominal pain alongside bleeding, or if you’re having chest pain or trouble breathing. Vomiting blood or material that looks like coffee grounds also warrants an ER visit.
Black, tarry stools specifically should prompt urgent evaluation, since they can indicate active bleeding in the stomach or upper intestine. This type of bleeding can be significant even if you feel relatively fine at first.
For smaller amounts of bright red blood, especially if it seems clearly related to straining or hard stools, it’s reasonable to monitor for a day or two. If the bleeding continues beyond that, or if it concerns you at all, schedule an appointment with your doctor rather than waiting it out.