Bloody stool is not normal, but it is common, and most of the time the cause is not serious. Hemorrhoids and small tears in the anus account for the majority of cases. That said, blood in or on your stool is always worth paying attention to because the color, amount, and accompanying symptoms can signal conditions ranging from minor to urgent.
What the Color of the Blood Tells You
The color of blood in your stool is a useful clue about where the bleeding is coming from. Bright red blood typically originates in the lower part of the digestive tract, usually the colon, rectum, or anus. Because the blood hasn’t traveled far, it stays red. This is the most common type people notice on toilet paper or in the bowl.
Black, tarry, sticky stool with a strong odor points to bleeding higher up in the digestive system, often the stomach or upper small intestine. Stomach acid and digestive enzymes break down the blood as it moves through your system, turning it dark. If your stool looks like this and you haven’t taken iron supplements, bismuth medications (like Pepto-Bismol), or eaten black licorice or blueberries, it warrants prompt medical attention.
Maroon-colored stool falls somewhere in between and may indicate bleeding in the upper colon or small intestine.
The Most Likely Causes
Two conditions cause the vast majority of bright red rectal bleeding: hemorrhoids and anal fissures. Both are extremely common and generally resolve on their own or with simple treatment.
Hemorrhoids are swollen veins in the rectum or around the anus, similar to varicose veins. They often produce noticeable bleeding, sometimes with larger clots, along with itching and a dull ache. External hemorrhoids can feel like lumps around the anus. Internal hemorrhoids may not be visible at all but still bleed, especially during a bowel movement. The bleeding is typically painless or mildly uncomfortable.
Anal fissures are small tears in the lining of the anus, usually caused by passing hard or large stools. They produce a sharp, burning pain that can last for hours after a bowel movement. Bleeding from a fissure tends to be a small amount of bright red blood on the toilet paper. Unlike hemorrhoids, fissures rarely cause swelling or lumps, and they’re more likely to sting or burn than itch.
A quick way to tell them apart: if the main problem is itching and you feel a lump, hemorrhoids are more likely. If the main problem is sharp, lasting pain during and after a bowel movement, think fissure.
Foods and Medications That Mimic Blood
Before assuming the worst, consider what you’ve eaten or taken recently. Beets and foods with red coloring can make stool appear reddish, closely mimicking the look of blood. On the darker end, iron pills, activated charcoal, bismuth-containing medications, black licorice, blueberries, and blood sausage can all turn stool black without any bleeding involved. If you’ve consumed any of these in the past day or two, that may explain what you’re seeing. The simplest test is to stop the suspected food or supplement and see if the color returns to normal within a couple of days.
When Bloody Stool Signals Something Deeper
Persistent or recurring blood in your stool, especially when accompanied by changes in bowel habits, abdominal pain, unexplained weight loss, or fatigue, can point to conditions that need diagnosis and treatment.
Inflammatory bowel disease (IBD), which includes ulcerative colitis and Crohn’s disease, is one of the more common causes of ongoing bloody stool. Ulcerative colitis causes inflammation in the colon and frequently produces bloody diarrhea. Crohn’s disease can affect any part of the digestive tract and causes patchy inflammation. Both conditions tend to come with cramping, urgency, and periods of flare-ups alternating with remission. It’s worth noting that irritable bowel syndrome (IBS), which is often confused with IBD, does not typically cause rectal bleeding. If you have IBS symptoms and start seeing blood, that’s a reason to get reevaluated.
Peptic ulcers, which are sores in the stomach or upper small intestine, cause upper GI bleeding. The hallmark sign is dark, tarry stool rather than bright red blood. You may also notice vomiting blood that looks red or dark like coffee grounds, along with dizziness or faintness from blood loss.
How Often Is It Cancer?
This is likely the fear behind your search, so here are the numbers. A study published in American Family Physician tracked 265 patients who came to their doctor with new-onset rectal bleeding. Colorectal cancer was diagnosed in about 5.7% of patients aged 45 and older. Another 4.9% had adenomas, which are precancerous polyps. That means roughly one in 10 patients in that age group who presented with rectal bleeding had some form of abnormal growth, but the other nine did not.
Those numbers are worth taking seriously without panicking. Your age matters significantly here. Rectal bleeding in someone under 40 with no family history of colorectal cancer is far less likely to indicate malignancy than the same symptom in someone over 50. But any persistent, unexplained bleeding deserves investigation regardless of age.
Current screening guidelines recommend that all adults begin routine colorectal cancer screening at age 45. Options range from annual stool-based tests to a colonoscopy every 10 years. If you’re 45 or older and haven’t started screening, bloody stool is a good reason to stop procrastinating.
Signs That Need Emergency Attention
Most rectal bleeding doesn’t require a trip to the emergency room. But certain combinations of symptoms do. Call 911 if you have significant rectal bleeding along with any of these signs of shock:
- Rapid, shallow breathing
- Dizziness or lightheadedness when standing
- Fainting or confusion
- Cold, clammy, or pale skin
- Blurred vision
- Very low urine output
- Nausea
You should also get to an emergency room if the bleeding is continuous or heavy (more than a few tablespoons), or if it comes with severe abdominal pain or cramping. Heavy, ongoing blood loss can become dangerous quickly even if you feel mostly fine at first.
What to Track Before Your Appointment
If you decide to see a doctor, which is a good idea for any bleeding that lasts more than a few days or keeps coming back, having specific details will help. Note the color of the blood (bright red, dark red, or black), whether it’s on the surface of the stool, mixed in, or only on the toilet paper, and how often it’s happening. Pay attention to whether you’re also experiencing pain, changes in stool consistency or frequency, fatigue, or unintentional weight loss.
Your doctor will likely start with a physical exam and may recommend a stool test that checks for hidden blood. Depending on your age, symptoms, and risk factors, a colonoscopy may be the next step. A colonoscopy allows direct visualization of the entire colon and is the most reliable way to identify or rule out polyps, inflammation, and cancer. The preparation is the unpleasant part. The procedure itself is done under sedation and typically takes 30 to 60 minutes, with most people going home the same day.