Blood in the toilet after a bowel movement is usually caused by hemorrhoids or a small tear in the skin around your anus. These two conditions account for the vast majority of cases, and both are treatable. That said, the color of the blood, the amount, and any other symptoms you’re experiencing all matter in determining what’s going on and whether you need medical attention.
What the Color of the Blood Tells You
The color of the blood is one of the most useful clues about where the bleeding is coming from. Bright red blood, whether on the toilet paper, dripping into the bowl, or coating the surface of your stool, typically means the bleeding source is close to the exit: your anus or rectum. This is the most common scenario and usually points to hemorrhoids or a fissure.
Dark red or maroon-colored blood mixed into the stool suggests bleeding higher up in the colon. This can happen with conditions like diverticular disease or inflammatory bowel disease. Black, tarry-looking stool is a different situation entirely. It usually means bleeding in the stomach or upper small intestine, where stomach acid breaks down the blood before it passes through. Peptic ulcers are a common cause of this type of bleeding.
One important note: certain foods and supplements can mimic the appearance of blood. Iron supplements and bismuth (the active ingredient in some stomach medications) can turn stool black. Beets and red food dye can make stool look reddish. If you’ve recently consumed any of these, that could explain what you’re seeing.
Hemorrhoids: The Most Common Cause
Hemorrhoids are swollen veins in your rectum or anus, and they’re the single most common cause of blood in stool. Internal hemorrhoids, which sit inside the rectum, tend to bleed painlessly. You might notice bright red blood on the toilet paper or in the bowl but feel nothing unusual. External hemorrhoids, which form under the skin around the anus, are more likely to cause discomfort, itching, or a noticeable lump.
Straining during bowel movements is the biggest trigger. Sitting on the toilet for long periods, chronic constipation, and pregnancy all increase your risk. Most hemorrhoids improve on their own or with simple changes like adding fiber to your diet, drinking more water, and avoiding straining.
Anal Fissures: When It Hurts to Go
If you feel a sharp, stinging pain during or after a bowel movement along with the bleeding, an anal fissure is the likely culprit. A fissure is a small tear in the lining of the anal canal, usually caused by passing a hard or large stool. The pain can linger as itching or burning that doesn’t go away quickly.
This is the key distinction between fissures and hemorrhoids. Hemorrhoids rarely cause significant pain. Fissures almost always do. Most fissures heal within a few weeks if you keep your stools soft and avoid constipation. Warm baths can also help relax the muscles around the area and promote healing.
Less Common but Important Causes
Diverticular Disease
Diverticulosis happens when small pouches form in the wall of the colon, which becomes increasingly common with age. These pouches are usually harmless, but if a small artery near one of them erodes, it can cause sudden, painless rectal bleeding. The hallmark of diverticular bleeding is that it comes on without abdominal pain, which makes it different from most other causes. The bleeding can be significant but often stops on its own.
Inflammatory Bowel Disease
Ulcerative colitis and Crohn’s disease both cause inflammation in the digestive tract that can lead to bleeding. Ulcerative colitis is limited to the colon and rectum and commonly causes bloody diarrhea, often with mucus. You might also experience belly cramps, urgency, and the frustrating sensation of needing to go but being unable to. Crohn’s disease can affect any part of the digestive tract and tends to involve deeper layers of the bowel wall. Both conditions also bring fatigue, weight loss, and recurring flare-ups over time.
Colon Polyps and Colorectal Cancer
Polyps are small growths on the inner lining of the colon. Most are benign, but some can develop into cancer over years. Both polyps and colorectal cancer can bleed when stool rubs against them as it passes through. This bleeding is often subtle, sometimes invisible to the naked eye, and may show up only on a lab test. The U.S. Preventive Services Task Force recommends colorectal cancer screening starting at age 45. If you’re under 45 and have bleeding along with unexplained weight loss, changes in bowel habits, or a family history of colon cancer, it’s worth getting checked sooner.
Medications
Blood thinners and anti-inflammatory pain relievers like ibuprofen and aspirin can cause or worsen GI bleeding. Taking a single low-dose blood thinner nearly doubles the risk of upper GI bleeding. Combining a blood thinner with aspirin raises the risk further. If you take any of these medications and notice blood in your stool, let your doctor know.
When Rectal Bleeding Is an Emergency
A small amount of bright red blood on toilet paper after a hard bowel movement is rarely dangerous. But certain situations call for immediate help. Go to an emergency room if the bleeding is continuous or heavy, or if it comes with severe abdominal pain or cramping.
Call 911 if you have significant bleeding along with any of these signs: dizziness or lightheadedness when you stand up, rapid or shallow breathing, fainting, confusion, blurred vision, nausea, cold or clammy skin, or very low urine output. These are signs your body is losing enough blood to affect circulation.
What Happens at the Doctor’s Office
If you go in for rectal bleeding, your doctor will likely start with blood work and may ask for a stool sample to confirm the presence of blood. From there, the tests depend on your symptoms and age. An anoscopy uses a small tube to look directly at the anus and check for hemorrhoids. A sigmoidoscopy examines the rectum and the lower part of the colon. A colonoscopy looks at the entire colon and rectum using a flexible camera while you’re sedated.
If your stool is black and tarry, or if you have signs of rapid blood loss like a fast heartbeat or low blood pressure, your doctor may also check your esophagus and stomach with an upper endoscopy. For bleeding that’s hard to locate, imaging tests can pinpoint the source by tracking blood flow through your vessels.
Preventing the Most Common Causes
Since hemorrhoids, fissures, and constipation are behind most cases of rectal bleeding, the same basic habits help prevent all three. The cornerstone is dietary fiber, which softens stool and makes it easier to pass without straining. Federal dietary guidelines recommend 14 grams of fiber per 1,000 calories you eat, which works out to about 28 grams per day on a standard 2,000-calorie diet. Good sources include beans, lentils, whole grains, fruits, and vegetables.
Drinking enough water matters just as much. Fiber absorbs water to do its job, so increasing fiber without increasing fluids can actually make constipation worse. Beyond diet, avoid sitting on the toilet longer than necessary (put the phone down), and don’t ignore the urge to go. Waiting too long allows stool to dry out in the colon, making it harder and more likely to cause problems on the way out.