Blood in your stool is surprisingly common, affecting roughly one in seven adults at some point, and most of the time the cause is minor. Hemorrhoids and small tears near the anus account for the majority of cases. That said, the color, amount, and accompanying symptoms all matter, because blood in stool can also signal conditions that need prompt attention.
What the Color of the Blood Tells You
The shade of blood you see is a useful clue to where the bleeding originates. Bright red blood on the toilet paper or in the bowl almost always comes from the lower digestive tract: the rectum, anus, or lower colon. Maroon or dark red blood mixed into the stool itself points to bleeding higher in the colon or small intestine.
Black, tarry, sticky stool is a different signal entirely. When blood is exposed to stomach acid during its journey through the digestive tract, it turns dark and takes on a tar-like consistency. This typically means the bleeding source is in the stomach or upper intestine, such as an ulcer. One important caveat: iron supplements, Pepto-Bismol, activated charcoal, black licorice, and large amounts of blueberries can all turn your stool black without any bleeding at all. Beets and red food coloring can make stool look reddish, mimicking blood. If you’ve recently eaten or taken any of these, that’s worth considering before you worry.
Hemorrhoids and Anal Fissures
These two conditions are the most frequent causes of bright red blood in stool, and they feel quite different from each other.
Hemorrhoids are swollen blood vessels in or around the anus. Internal hemorrhoids, the kind inside the rectum, typically don’t hurt at all. You might notice blood on the toilet paper or dripping into the bowl after a bowel movement, with little or no pain. External hemorrhoids, which form under the skin around the anus, can cause itching and mild discomfort, especially if a blood clot develops inside them.
Anal fissures are small tears in the lining of the anus, usually caused by passing hard or large stools. Unlike hemorrhoids, fissures are more likely to cause sharp pain during and after a bowel movement. You’ll typically see a small amount of bright red blood on the toilet paper. The pain often feels like a burning or tearing sensation that can linger for minutes to hours. Most fissures heal on their own within a few weeks with increased fiber and water intake to soften stools.
Inflammatory Bowel Disease
Ulcerative colitis causes inflammation and sores in the lining of the colon and rectum. About a million Americans have it, and it can develop at any age, including in your 20s and 30s. The hallmark is bloody diarrhea, often with a strong urgency to go, belly pain, fatigue, and unintentional weight loss. The bleeding tends to be persistent rather than occasional, and you may notice mucus mixed with blood in the stool.
Crohn’s disease, the other major form of inflammatory bowel disease, can affect any part of the digestive tract. Bleeding is less consistently visible than with ulcerative colitis, but it can cause blood in the stool along with abdominal cramping, diarrhea, and weight loss. Both conditions are chronic and require ongoing management, but treatments can effectively control symptoms for most people.
Diverticular Bleeding
Diverticulosis, the formation of small pouches in the colon wall, becomes extremely common with age. About half of people over 60 have it, and nearly everyone over 80 does. Most people with diverticulosis never know they have it. But between 5% and 15% develop symptoms, and one of those symptoms can be sudden, painless rectal bleeding that’s often heavy enough to be alarming.
Diverticular bleeding typically produces a large amount of dark red or maroon blood. It often stops on its own, but it can be significant enough to require medical evaluation. If diverticulosis progresses to diverticulitis (infection or inflammation of the pouches), you’re more likely to have belly pain, fever, nausea, bloating, and constipation alongside any bleeding.
Stomach and Upper GI Bleeding
Peptic ulcers, which are open sores in the stomach lining or the first part of the small intestine, are the most common source of upper digestive tract bleeding. When blood from an ulcer moves through your digestive system, stomach acid breaks it down, producing that characteristic black, tarry stool. You might also have a burning stomach pain that worsens when your stomach is empty, nausea, or a feeling of fullness.
Other causes of upper GI bleeding include inflammation of the stomach lining (often from frequent use of anti-inflammatory painkillers like ibuprofen or naproxen) and, less commonly, tears in the esophagus from severe vomiting. Upper GI bleeding always warrants medical attention, because even slow, ongoing blood loss can lead to anemia over time.
Polyps and Colorectal Cancer
Colorectal polyps are small growths on the inner wall of the colon or rectum. Most are harmless, but some can develop into cancer over years. Polyps and early-stage colorectal cancer often cause no symptoms at all, which is why screening matters. When they do bleed, the blood may be invisible to the naked eye and only detected through a stool test.
The U.S. Preventive Services Task Force recommends colorectal cancer screening starting at age 45 for people at average risk. If you have a family history of colorectal cancer or certain genetic conditions, screening may need to start earlier. Screening options include stool-based tests done at home (though these detect only about 25% of advanced growths per cycle, which is why they’re repeated regularly) and colonoscopy, which can both find and remove polyps in the same procedure.
Blood in stool that’s new, persistent, or accompanied by a change in bowel habits, unexplained weight loss, or narrowing of the stool is worth getting evaluated regardless of your age or screening status.
Signs That Need Immediate Attention
Most rectal bleeding doesn’t require a trip to the emergency room. A small amount of bright red blood after straining, without other symptoms, can usually wait for a scheduled appointment with your doctor. But certain combinations of symptoms signal a potentially serious bleed that needs urgent care.
Call 911 or get to an emergency room if rectal bleeding is continuous or heavy, or if it comes with any of these signs:
- Dizziness or lightheadedness when you stand up
- Rapid, shallow breathing
- Cold, clammy, or pale skin
- Confusion or fainting
- Blurred vision
- Severe abdominal pain or cramping
- Very low urine output
These symptoms suggest your body is losing blood faster than it can compensate. Significant blood loss from the GI tract can drop blood pressure quickly, and that combination requires emergency evaluation. Even if the bleeding stops on its own, the presence of these symptoms means you should be seen right away.