Blood in your stool usually comes from somewhere in your digestive tract, and the color tells you a lot about where. In most cases, the cause is something minor and treatable like hemorrhoids or a small tear near the anus. But because bleeding can also signal more serious conditions, it’s worth understanding what different types of bleeding look like and when to take action.
What the Color Tells You
The color of the blood is the single most useful clue about where the bleeding is coming from. Bright red blood typically means the source is lower in your digestive tract, usually the colon, rectum, or anus. Because the blood hasn’t traveled far, it still looks fresh. You might see it on toilet paper, in the bowl, or coating the surface of your stool.
Black, tarry stool points to bleeding higher up, usually in the stomach or upper small intestine. The blood turns jet black and sticky as it’s digested during its long trip through the GI tract. This type of stool has a distinctive look and a notably foul smell that’s different from normal bowel movements. If you notice this, it generally warrants prompt medical attention because upper GI bleeding tends to involve more significant conditions like ulcers.
Maroon-colored stool falls in between and may indicate bleeding in the middle of the digestive tract, such as the lower small intestine or the right side of the colon.
The Most Common Causes
The three most frequent reasons for bright red blood in stool are hemorrhoids, anal fissures, and hard stools from constipation. Hemorrhoids are swollen veins in or around the rectum that bleed when irritated, especially during straining. Anal fissures are tiny tears in the lining of the anal canal, often caused by passing large or hard stools. These conditions are uncomfortable but not dangerous, and they typically respond to dietary changes, more fiber, and better hydration.
Less common but more serious causes include colon polyps (small growths on the colon lining that can sometimes become cancerous), diverticulosis (small pouches that bulge outward from the intestinal wall and occasionally bleed), and colorectal cancer. Inflammatory bowel diseases like Crohn’s disease and ulcerative colitis also cause rectal bleeding, usually alongside diarrhea, abdominal pain, fatigue, and weight loss. In ulcerative colitis, bloody diarrhea is one of the hallmark symptoms.
Painkillers and Stomach Bleeding
Over-the-counter anti-inflammatory drugs like ibuprofen and aspirin are a surprisingly common cause of digestive bleeding. Among people who take these medications regularly, peptic ulcer rates range from 15 to 40 percent, and the risk of serious upper GI complications is three to five times higher than in people who don’t use them. That risk increases with dose and duration, and it’s higher in older adults, people taking multiple medications, and those with an existing bacterial stomach infection.
Surveys have found that roughly one in four people who buy these medications over the counter exceed the recommended dose. If you’re using anti-inflammatory painkillers frequently and notice dark or tarry stools, the medication itself may be the source of the bleeding.
Foods and Supplements That Mimic Blood
Before you panic, consider what you’ve eaten or taken recently. Several common foods and supplements can make stool look bloody when it isn’t. Beets, red gelatin, red fruit punch, red licorice, and red-dyed snack foods can all make stool appear red. On the dark side, iron supplements, bismuth-containing stomach medicines (like Pepto-Bismol), activated charcoal, blueberries, and large amounts of dark leafy greens like spinach or kale can turn stool black.
If you recently consumed any of these and feel otherwise fine, that’s likely your explanation. The discoloration should clear within a day or two after you stop eating the culprit food.
How Doctors Find the Source
If the bleeding persists, your doctor will typically start with simple tests before moving to more involved procedures. A fecal immunochemical test (FIT) checks for hidden blood in your stool that you can’t see with the naked eye. It’s about 80 percent accurate at detecting colorectal cancer, though it’s less sensitive for precancerous growths, catching only 20 to 30 percent of advanced polyps. It’s a straightforward at-home test where you collect a small stool sample and send it to a lab.
A colonoscopy is the most thorough option. A flexible camera is guided through the entire colon, allowing your doctor to both find and remove polyps during the same procedure. The U.S. Preventive Services Task Force recommends routine colorectal cancer screening for all adults starting at age 45, with colonoscopies every 10 years or stool-based tests annually as the main options. If you’re already experiencing bleeding, your doctor may recommend a colonoscopy regardless of your age or when you were last screened.
Signs That Need Immediate Attention
Most rectal bleeding is not an emergency, but some situations call for urgent care. Get 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 rectal bleeding along with any signs that your body is losing too much blood too quickly. These include:
- Dizziness or lightheadedness when you stand up
- Rapid, shallow breathing
- Fainting or confusion
- Blurred vision
- Nausea
- Cold, clammy, or pale skin
- Very low urine output
These are signs of shock, meaning your blood pressure is dropping to dangerous levels. This is rare with rectal bleeding, but it requires immediate treatment.
What to Track Before Your Appointment
If your bleeding is mild and you plan to see a doctor soon, paying attention to a few details beforehand will help them narrow down the cause faster. Note the color of the blood (bright red, dark red, or black), whether it’s mixed into the stool or only on the surface, how often it happens, and whether you have any other symptoms like pain, changes in bowel habits, or unintentional weight loss. Also note any medications you take regularly, especially anti-inflammatory painkillers, blood thinners, or supplements like iron.
A single episode of bright red blood on toilet paper after straining is almost always from hemorrhoids or a fissure. Recurrent bleeding, blood mixed into the stool, or dark and tarry stool patterns are the ones that warrant a closer look.