Blood when you poop is usually caused by hemorrhoids or a small tear in the skin around your anus. These two conditions account for the vast majority of rectal bleeding, and both are closely tied to straining during bowel movements. That said, blood in your stool can also signal something more serious, so the color, amount, and any accompanying symptoms all matter.
What the Color of the Blood Tells You
The color of the blood is the single most useful clue about where the bleeding is coming from. Bright red blood on the toilet paper, on the surface of your stool, or dripping into the bowl points to bleeding in the lower part of your digestive tract, typically the rectum or anus. This is the most common scenario and usually the least serious.
Maroon or dark red blood mixed into the stool suggests bleeding higher up in the colon. Black, tarry, sticky stool (not just dark brown) can indicate bleeding in the upper digestive system, like the stomach or small intestine. Blood that travels a long distance through the gut gets digested along the way, which turns it dark. Keep in mind that iron supplements, bismuth medications like Pepto-Bismol, and even large amounts of blueberries can also make stool look black, so don’t panic before considering what you’ve eaten or taken recently.
Hemorrhoids: The Most Common Cause
Hemorrhoids are swollen veins in the rectum or anus, and they’re the number one reason people see blood when they wipe or look in the toilet. They develop from pressure on those veins, most often from straining during constipation, sitting on the toilet too long, pregnancy, or heavy lifting.
Internal hemorrhoids sit inside the rectum where there are few pain-sensing nerves, so they rarely hurt. What they do is bleed, sometimes enough to turn the toilet water red. You typically won’t feel or see an internal hemorrhoid unless it prolapses (pushes out through the anus), in which case it feels like a small, soft lump you can often push back in.
External hemorrhoids form under the skin around the outside of the anus. They’re more likely to itch and ache, especially when you sit, and they sometimes bleed when you wipe. If a blood clot forms inside one (a thrombosed hemorrhoid), it becomes a firm, tender lump that can look blue, black, or purple. This is painful but not dangerous, and it usually resolves on its own over a week or two.
Anal Fissures
An anal fissure is a small tear in the lining of the anal canal. It happens when the tissue stretches beyond its limit, usually from passing a large or hard stool. The telltale sign is a sharp, stinging pain during a bowel movement along with a streak of bright red blood on the stool or toilet paper. The pain can linger for minutes to hours afterward.
Tight muscles around the anus can make fissures more likely by adding tension to the lining and reducing blood flow to the tissue. Most anal fissures heal within a few days to weeks with basic care: keeping stools soft, staying hydrated, and avoiding straining. Warm baths (sitz baths) can help relax the muscles and ease discomfort during healing.
Inflammatory Bowel Disease
If you’re seeing blood in your stool regularly, especially mixed with diarrhea, inflammatory bowel disease (IBD) is worth knowing about. The two main types, ulcerative colitis and Crohn’s disease, affect different parts of the digestive tract and show up differently.
Ulcerative colitis starts at the rectum and stays within the colon. Its hallmark symptoms are bloody diarrhea, sudden urgent trips to the bathroom, and a frustrating feeling that you still need to go even right after a bowel movement. Cramps and bleeding are centered in the lower abdomen. Crohn’s disease, by contrast, mostly affects the small intestine and tends to cause belly pain with non-bloody diarrhea and unintended weight loss. Bleeding is less prominent in Crohn’s than in ulcerative colitis, though it can occur.
Diverticular Bleeding
Diverticulitis occurs when small pouches that form in the lining of the colon become infected and inflamed. These pouches (diverticula) are common in people over 40 and usually cause no problems. But when they bleed, it can be sudden and produce a significant amount of maroon or bright red blood. Diverticular bleeding often stops on its own, but the volume can be alarming enough to warrant medical evaluation.
Colorectal Cancer
Rectal bleeding is a possible symptom of colorectal cancer, though it’s far less common than hemorrhoids or fissures. What sets cancer apart is that it rarely causes bleeding alone. Persistent changes in bowel habits (new constipation or diarrhea lasting weeks), unexplained weight loss, fatigue, and a feeling that your bowel doesn’t empty completely are patterns that deserve attention.
The U.S. Preventive Services Task Force recommends that all adults begin routine colorectal cancer screening at age 45 and continue through age 75. If you have a family history of colorectal cancer or polyps, screening may need to start earlier. Catching polyps before they turn cancerous is the whole point of screening, and it’s one of the most effective cancer prevention tools available.
How Doctors Figure Out the Cause
If you bring up rectal bleeding with your doctor, the workup typically starts simple. A physical exam, including a visual and digital check of the anal area, can identify hemorrhoids and fissures quickly. Blood tests may be ordered to check for anemia (low red blood cell count from ongoing blood loss) and to see how well your blood clots.
A stool test can detect hidden blood you can’t see with the naked eye. If the cause isn’t obvious from the exam, a colonoscopy is the standard next step. During a colonoscopy, a flexible tube with a tiny camera is guided through the rectum and into the entire large intestine, letting your doctor see the source of bleeding directly and take tissue samples if needed. For suspected upper digestive bleeding, a similar camera is passed down the throat to examine the stomach and upper intestines.
What You Can Do at Home
Since the most common causes of rectal bleeding are tied to hard stools and straining, the most effective thing you can do is keep your bowel movements soft and easy to pass. That starts with fiber. Current dietary guidelines recommend about 14 grams of fiber per 1,000 calories you eat, which works out to roughly 28 grams per day on a standard 2,000-calorie diet. Most people fall well short of that. Fruits, vegetables, beans, whole grains, and psyllium husk supplements are practical ways to close the gap.
Drink plenty of water alongside the extra fiber, because fiber without enough fluid can actually make constipation worse. Avoid sitting on the toilet longer than necessary (put the phone down), and don’t ignore the urge to go. Warm sitz baths, where you sit in a few inches of warm water for 10 to 15 minutes, can soothe both hemorrhoids and fissures.
Signs That Need Urgent Attention
A small amount of bright red blood on the toilet paper after a hard bowel movement is common and usually not an emergency. But certain combinations of symptoms signal that you’re losing too much blood or that something more serious is happening. Get emergency medical help if rectal bleeding comes with any of the following:
- Dizziness or lightheadedness when you stand up
- Rapid, shallow breathing
- Fainting or confusion
- Cold, clammy, pale skin
- Blurred vision
- Nausea
- Very low urine output
These are signs of shock from significant blood loss and require immediate care. Even without those red flags, rectal bleeding that keeps coming back over weeks, gets heavier over time, or is accompanied by unexplained weight loss or persistent changes in your bowel habits is worth getting evaluated sooner rather than later.