Blood in Stool and Cancer: What It Means, Causes, and Management

Seeing blood in your stool can be alarming, and it’s understandable to worry about cancer. Blood in or on the stool can be a symptom of colorectal cancer, but it also commonly comes from non-cancer causes like hemorrhoids, anal fissures, or diverticular disease. ^[1] Blood in stool is one of several warning signs that should prompt medical evaluation, especially if it persists for more than two weeks, recurs, or is accompanied by changes in bowel habits, anemia, or unexplained weight loss. ^{[2] [3]}

Is blood in stool a common cancer symptom?

• Blood in or on the stool is a recognized symptom of colorectal cancer, along with rectal bleeding and changes in bowel habits. ^{[1] [3]}
• However, many colorectal cancers and precancerous polyps cause no symptoms early on, which is why routine screening is so important. ^{[1] [3]}
• When bleeding is present, cancer is one possible cause among several; not all rectal bleeding is cancer. ^[4]

Other common causes of blood in stool

• Hemorrhoids (swollen anal/rectal veins) and anal fissures (small tears) are frequent, benign sources of bright-red rectal bleeding. ^[5]
• Diverticular disease (diverticulosis/diverticulitis) can cause lower gastrointestinal bleeding. ^[6]
• Inflammatory bowel disease (ulcerative colitis or Crohn’s disease) may lead to rectal bleeding and bloody diarrhea. ^{[6] [4]}
• Colorectal polyps and benign or cancerous tumors can bleed. ^{[7] [4]}
• Less commonly, infections, proctitis (rectal inflammation), or trauma can cause bleeding. ^{[7] [8]}

Related symptoms to watch for

• Changes in bowel habits (diarrhea, constipation, or feeling incompletely emptied) can accompany colorectal cancer. ^[1]
• Narrow or thin stools, fatigue, anemia, and unintentional weight loss may also occur. ^[3]
• Persistent rectal bleeding or blood in the stool for two weeks or more warrants prompt medical attention. ^[2]

When to seek care urgently

• Heavy bleeding, black or maroon stools, dizziness, fainting, or severe abdominal pain require urgent evaluation. ^[6]
• Even small amounts of blood that recur or persist should be assessed to find the cause and rule out serious conditions. ^[8]

How doctors find the cause

• A clinician will review your symptoms and examine you, often followed by stool tests and bloodwork (to check for anemia or inflammation). ^[9]
• Colonoscopy is the gold standard to diagnose causes of lower GI bleeding, allowing direct visualization and biopsies of the colon and rectum. ^[9]
• Depending on findings, imaging or additional tests may be used to complete the evaluation. ^[3]

Management and treatment options

Treatment depends on the cause identified:

• Hemorrhoids or fissures: Fiber, fluids, stool softeners, sitz baths, topical medicines; procedures if severe. ^[5]
• Diverticular bleeding: Observation if minor; endoscopic treatment, angiography, or surgery if significant. ^[6]
• Inflammatory bowel disease: Anti-inflammatory and immune-modulating medicines, with colonoscopy monitoring. ^{[6] [9]}
• Polyps: Endoscopic removal to prevent progression and stop bleeding. ^[7]
• Colorectal cancer: Management may include surgery, chemotherapy, radiation, and targeted therapies, guided by stage and tumor location. ^{[3] [10]}

Prevention and self-care tips

• Keep stools soft with adequate fiber and hydration to reduce hemorrhoid and fissure bleeding. ^[5]
• Don’t ignore ongoing rectal bleeding; tracking frequency, color, and associated symptoms helps your clinician. ^[8]
• Stay up to date with colorectal cancer screening, as screening can find and remove polyps before they become cancer or detect cancer early when it’s most treatable. ^{[1] [3]}

At-a-glance summary

• Blood in stool can be caused by benign issues or by colorectal cancer; both deserve attention. ^{[1] [3]}
• Persistent or recurrent bleeding should be medically evaluated, with colonoscopy often needed to confirm the cause. ^[9]
• Treatment is tailored to the cause and may range from diet and topical therapies to endoscopic removal of polyps or comprehensive cancer care. ^{[7] [3]}

If you are noticing blood in your stool now, especially if it has lasted more than two weeks or is accompanied by changes in bowel habits or fatigue, it would be reasonable to arrange a medical evaluation to identify the cause and get appropriate care. ^{[2] [1] [3]}