Blood in your stool is alarming, but in most cases it comes from something treatable and not life-threatening. Hemorrhoids and small tears in the skin around the anus account for the majority of rectal bleeding, especially in younger adults. That said, the color, amount, and accompanying symptoms all matter, and some patterns do require urgent attention.
What the Color of the Blood Tells You
The color is your first clue about where the bleeding is coming from. Bright red blood typically originates in the lower digestive tract: the rectum, anus, or lower colon. This is the most common type people notice on toilet paper or in the bowl. It usually points to a problem close to the exit, like hemorrhoids or a fissure.
Black, tarry stools are a different story. When blood starts higher up in the digestive tract (the stomach or upper intestines), it gets broken down by digestive enzymes on its way through. By the time it reaches the toilet, the blood has turned dark and sticky. This type of bleeding can indicate ulcers or other upper GI problems and generally warrants faster medical attention than a streak of bright red on toilet paper.
Maroon or dark red blood falls somewhere in between and may come from the middle of the digestive tract, such as the small intestine or the right side of the colon.
The Most Common Causes
Hemorrhoids are swollen blood vessels in and around the anus. They’re extremely common and often cause painless bright red bleeding during or after a bowel movement. You might see blood on the toilet paper, dripping into the bowl, or coating the surface of the stool. Hemorrhoids can itch or feel uncomfortable, but many people have them without any pain at all.
Anal fissures are small tears in the lining of the anal canal. About half of people who get them are under 40, and they’re especially common in infants and pregnant women. Unlike hemorrhoids, fissures almost always hurt. Around 90% of fissures cause sharp pain during a bowel movement, often with a burning or stinging sensation. Both conditions tend to develop from straining, constipation, or passing hard stools.
If you’ve been straining lately, had constipation, or eaten a low-fiber diet, one of these two causes is the most likely explanation for bright red blood.
Infections That Cause Bloody Stool
Food poisoning and bacterial infections can inflame the lining of the intestines enough to cause bleeding. The most common culprits are Campylobacter, certain strains of E. coli, Salmonella, and Shigella. If your bloody stool came on suddenly alongside diarrhea, stomach cramps, fever, or vomiting, an infection is a strong possibility. Most cases of bacterial gastroenteritis resolve on their own within a few days, but bloody diarrhea with a high fever or signs of dehydration needs medical evaluation.
Inflammatory Bowel Disease
Ulcerative colitis and Crohn’s disease are chronic conditions that cause ongoing inflammation in the digestive tract. Ulcerative colitis in particular is known for bloody diarrhea, sometimes with mucus or pus. Other symptoms that tend to accompany IBD include persistent abdominal cramping, fatigue, unintended weight loss, loss of appetite, fever, and rectal urgency (feeling like you need to go but can’t). In children, it can delay growth and development.
These symptoms typically develop gradually over weeks or months rather than appearing overnight. If you’ve had recurring bloody stools along with several of these other symptoms, IBD is worth investigating. A definitive diagnosis requires a biopsy taken during a scope procedure, but imaging tests can also help assess the extent of inflammation.
Conditions More Common in Older Adults
Diverticular bleeding happens when small pouches that form in the colon wall (diverticula) start to bleed. It’s one of the most common causes of significant rectal bleeding in people over 60. The bleeding is typically painless but can be heavy, producing large amounts of bright red or maroon blood.
Angiodysplasia is another condition seen primarily in older adults. It involves fragile, abnormal blood vessels in the colon wall that can leak blood intermittently. Some people experience mild episodes, while others have bouts of significant bleeding with bright red or black stool.
Could It Be Colorectal Cancer?
This is the fear behind most searches like this one. Colorectal cancer can cause rectal bleeding, but it’s far less common than hemorrhoids or fissures, particularly in younger adults. Cancer-related bleeding is more likely to be persistent, accompanied by changes in bowel habits (new constipation or narrower stools), unexplained weight loss, or a feeling that the bowel doesn’t fully empty.
The U.S. Preventive Services Task Force recommends colorectal cancer screening for all adults starting at age 45 and continuing through age 75. Several screening options exist, from annual at-home stool tests that detect hidden blood or abnormal DNA, to a colonoscopy every 10 years. A positive result on a stool test always requires a follow-up colonoscopy, since stool tests can flag problems but can’t directly examine the colon or remove polyps.
If you’re under 45 with no family history and your bleeding is clearly linked to straining or constipation, cancer is unlikely. But any rectal bleeding that persists for more than a week or two, or that you can’t easily explain, is worth bringing to your doctor regardless of your age.
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 fresh blood. On the dark end, iron supplements, black licorice, blueberries, activated charcoal, and bismuth-based medications (the active ingredient in Pepto-Bismol) can all turn stool black in a way that looks like digested blood. If you recently consumed any of these, that may be the entire explanation.
What Happens at the Doctor’s Office
Your doctor will likely ask about the color and amount of blood, how long it’s been happening, your bowel habits, diet, and any other symptoms. A physical exam often includes a visual inspection and sometimes a brief rectal exam.
If the cause isn’t obvious from the exam, the next step is usually a colonoscopy, which uses a flexible camera to examine the entire colon and rectum. This can identify hemorrhoids, fissures, polyps, areas of inflammation, diverticular disease, and cancer. If only the lower portion needs checking, a sigmoidoscopy examines just the rectum and lower colon. Findings during a sigmoidoscopy sometimes lead to a full colonoscopy for a more complete picture.
Signs You Need Emergency Care
Most rectal bleeding doesn’t require an emergency room visit, but some situations do. Call 911 or get to an ER if you’re experiencing heavy or continuous bleeding alongside any of these signs:
- Dizziness or lightheadedness when standing
- Rapid, shallow breathing
- Fainting or confusion
- Blurred vision
- Cold, clammy, or pale skin
- Very low urine output
- Nausea
These are signs your body is losing enough blood to affect circulation. You should also seek immediate care if rectal bleeding is accompanied by severe abdominal pain or cramping, even without the symptoms listed above. Heavy, nonstop bleeding is always an emergency regardless of other symptoms.