Blood in your poop is usually caused by something minor like hemorrhoids or a small tear near the anus, but it can also signal conditions that need medical attention. The color, amount, and timing of the blood all give clues about where the bleeding is coming from and how seriously to take it.
What the Color of the Blood Tells You
The color of blood in your stool is directly tied to where the bleeding originates in your digestive tract. Bright red blood typically comes from the lower part of the tract, near the rectum or anus. Because it hasn’t traveled far, it stays red. You might see it on the toilet paper, coating the outside of the stool, or in the toilet bowl.
Dark red or maroon blood usually means the bleeding is higher up, somewhere in the colon. Black, tarry stools point to bleeding even further up, often in the stomach or upper small intestine. The blood turns dark because hemoglobin (the protein in red blood cells) breaks down as it passes through the digestive system and gets exposed to stomach acid and digestive enzymes. By the time it reaches the other end, it looks black and has a sticky, tar-like consistency.
The Most Common Causes
A small amount of bright red blood on toilet paper or on the surface of stool is most often caused by hemorrhoids or an anal fissure. Hemorrhoids are swollen blood vessels in the rectum or anus that bleed when irritated, especially during a bowel movement. Anal fissures are tiny tears in the lining of the anus, usually caused by passing a large or hard stool. Both are uncomfortable but not dangerous, and they account for the vast majority of rectal bleeding in adults.
Other common causes include diverticulosis, where small pouches in the colon wall bleed (often painlessly), and inflammatory bowel diseases like Crohn’s disease or ulcerative colitis, which cause chronic inflammation and can produce blood mixed into the stool along with diarrhea and abdominal pain. Infections from bacteria like Salmonella, Shigella, or E. coli can cause bloody diarrhea that typically comes on suddenly and may be accompanied by fever and cramping.
Medications That Increase Bleeding Risk
Certain medications make gastrointestinal bleeding more likely. Over-the-counter pain relievers like ibuprofen, naproxen, and diclofenac can irritate the stomach lining and cause bleeding, especially with regular use. If you’re already taking a blood thinner, adding one of these painkillers more than doubles your risk of a gut bleed. The combination with naproxen raises the risk by about four times, and diclofenac by about three times. Even ibuprofen, which many people consider mild, increases the risk nearly twofold when combined with a blood thinner.
If you take blood thinners and notice blood in your stool, that’s worth a prompt call to your doctor, since you may be bleeding more than you realize.
Foods That Mimic Blood in Stool
Before you panic, consider what you ate recently. Several foods and supplements can make stool look bloody when it isn’t. Beets are the most common culprit. They contain a pigment called betalain that the body struggles to break down, and it can turn stool red or pink for a day or two. Eating large amounts of tomatoes, red peppers, cranberries, or other red berries can do the same.
Artificial food dyes, especially Red 40 (found in candies, gelatin, and flavored drinks), pass through the body mostly unabsorbed and show up in stool. Iron supplements can make stool black or very dark, which looks alarming but is harmless. Bismuth-based stomach medications like Pepto-Bismol also turn stool black because the active ingredient reacts with sulfur in the gut. If your stool color returns to normal within a day or two of stopping the suspect food or supplement, bleeding is unlikely.
How Likely Is It to Be Cancer?
This is the fear behind most searches about blood in stool, and the numbers are reassuring for most people. In a study of adults 45 and older who visited their primary care doctor with new rectal bleeding, about 5.7% were eventually diagnosed with colorectal cancer. Among those aged 45 to 54, the rate was even lower, around 4%. It rose to roughly 9.5% in the 65-to-74 age group. That means even in the higher-risk age brackets, more than 9 out of 10 people with rectal bleeding had something other than cancer causing it.
That said, about 1 in 10 patients in the study had some type of abnormal growth (either cancer or precancerous polyps), which is why new rectal bleeding in anyone over 45 is taken seriously and typically leads to further testing. Younger adults with no other symptoms and an obvious cause like hemorrhoids are at much lower risk, though persistent or unexplained bleeding at any age deserves evaluation.
Blood in a Baby’s or Child’s Stool
In children, the most common cause of blood in stool is an anal fissure, accounting for about 90% of cases. This happens when a child passes a large or hard stool that tears the delicate skin around the anus. It usually looks like a streak of bright red blood on the outside of the stool or on the diaper.
In infants under two months old, blood-streaked and slimy stools can be a sign of cow’s milk protein allergy, sometimes called cow’s milk colitis. This is common in formula-fed babies and typically improves when the formula is switched. Bacterial infections causing bloody diarrhea (from organisms like Shigella, Salmonella, or E. coli) are another possibility, especially if the child also has a fever. Less commonly, a strep skin infection around the anus can cause blood-streaked stools in young children.
What Testing Looks Like
If your doctor wants to investigate blood in your stool, the process usually starts simple. A fecal occult blood test checks for hidden blood that isn’t visible to the naked eye. It involves collecting a small stool sample at home or in a clinical setting. This test can confirm that blood is present, but it can’t tell you why, so a positive result almost always leads to further testing.
The most common next step is a colonoscopy, where a thin, flexible tube with a camera is guided through the entire colon. This lets the doctor see the source of bleeding directly and, if polyps are found, remove them during the same procedure. A sigmoidoscopy is a shorter version that only examines the lower portion of the colon. For people who can’t or prefer not to have a standard colonoscopy, a CT colonography (sometimes called a virtual colonoscopy) uses imaging to create detailed pictures of the colon without inserting a scope, though it can’t remove polyps if any are found. A stool DNA test is another option that checks for genetic markers associated with colorectal polyps or cancer.
Signs That Need Immediate Attention
Most rectal bleeding doesn’t require a trip to the emergency room, but certain signs indicate significant blood loss that needs urgent care. If you’re experiencing rectal bleeding along with rapid or shallow breathing, dizziness when standing, blurred vision, fainting, confusion, nausea, cold or clammy skin, or very low urine output, these are signs of shock from blood loss. This combination calls for emergency medical help right away.
Large volumes of blood, whether bright red or dark, also warrant immediate evaluation. The same goes for blood in the stool that comes with severe abdominal pain, high fever, or unexplained weight loss. A single episode of a few drops of bright red blood after straining is a very different situation from ongoing bleeding with systemic symptoms, and your response should match accordingly.