What Is Bloody Diarrhea?

Bloody diarrhea—also called bloody stool or rectal bleeding—appears when loose, watery stools contain visible blood. The blood may be bright red, dark red, or black and tar-like.

Common causes include anal fissures, hemorrhoids, infections, inflammatory bowel diseases (IBD), ulcers, and in rare cases, colorectal cancer.

Although diarrhea often resolves on its own, blood in stool should never be ignored. A healthcare provider can help identify the cause and recommend the right treatment.

What Does Blood in Diarrhea Look Like?

Blood may appear:

  • On the surface of stool

  • Mixed with watery diarrhea

  • On toilet paper after wiping

  • Floating in the toilet bowl

Bright red blood usually means bleeding low in the colon or rectum (e.g., hemorrhoids).
Dark red or black stools suggest bleeding higher up in the digestive tract.

Common Causes of Bloody Diarrhea

Anal Fissures

  • Tiny tears in the lining of the anus, often caused by straining from constipation or sometimes chronic diarrhea.

  • Painful bowel movements with bright red blood are typical.

Hemorrhoids

  • Swollen veins in the rectum or anus.

  • One of the most common causes of blood in stool.

  • Blood is usually bright red and may coat the stool or show on toilet paper.

Infections

  • Diverticulitis: inflamed pouches in the colon wall may bleed heavily.

  • Infectious colitis or food poisoning: bacterial, viral, or parasitic infections.

  • Sexually transmitted infections (STIs): gonorrhea, syphilis, herpes, or chlamydia can affect the rectum and cause bleeding.

Inflammatory Conditions

  • Inflammatory bowel disease (IBD), especially ulcerative colitis, commonly causes bloody diarrhea.

  • Proctitis (inflammation of the rectum) may also occur from IBD, STIs, or radiation therapy.

Peptic Ulcers

  • Ulcers in the stomach or small intestine may erode blood vessels, causing black, tarry stools.

Colorectal Cancer

  • Tumors in the colon or rectum may bleed, producing dark stools or bright red blood.

  • Persistent or unexplained rectal bleeding requires urgent medical evaluation.

Causes in Children

  • The most common reason is constipation, leading to anal fissures or hemorrhoids.

  • Other possible causes: infections, IBD, peptic ulcers, or Meckel’s diverticulum (a congenital intestinal pouch).

When To Seek Emergency Care

Call a healthcare provider right away if you experience:

  • Heavy or persistent bleeding

  • Severe abdominal pain or cramping

  • High fever

  • Black or tarry stools

  • Vomiting or inability to keep fluids down

  • Signs of dehydration (dry mouth, dizziness, low urine output, sunken eyes)

Children should be evaluated immediately if they have excessive crying during bowel movements, abdominal swelling, weight loss, or bloody diapers.

How Is Bloody Diarrhea Diagnosed?

Diagnosis usually begins with a health history and physical exam. Tests may include:

  • Anoscopy or sigmoidoscopy – to view the rectum and lower colon

  • Colonoscopy – to examine the entire colon

  • Stool culture – to check for infections

  • Blood tests – to detect anemia or signs of infection

Treatment Options

General Care

  • Hydration is key: use oral rehydration solutions, broths, diluted juices, or IV fluids for severe dehydration.

  • Eat a bland diet: bananas, rice, applesauce, toast, oatmeal.

  • Avoid alcohol, caffeine, spicy foods, and greasy meals.

Cause-Specific Treatments

  • Anal fissures/hemorrhoids: stool softeners, sitz baths, topical ointments; surgery for severe cases.

  • Infections: antibiotics or antiparasitic medications when needed.

  • IBD/proctitis: anti-inflammatory drugs, immunosuppressants, or biologics.

  • Ulcers: proton pump inhibitors, H. pylori eradication therapy.

  • Colorectal cancer: surgery, chemotherapy, or radiation.

  • Severe bleeding: hospitalization, blood transfusions if necessary.

Prevention Tips

  • Avoid straining and don’t sit too long on the toilet.

  • Eat a fiber-rich diet (whole grains, fruits, vegetables).

  • Stay hydrated.

  • Practice good hygiene to prevent infections.

  • Use condoms to prevent STI-related rectal infections.

  • Get regular screenings for colorectal cancer after age 45 or earlier if at higher risk.

Complications

If untreated, bloody diarrhea may cause:

  • Dehydration and electrolyte imbalance → dizziness, fainting, kidney issues.

  • Anemia from chronic blood loss.

  • Severe infections or shock in rare cases.

Quick Review

  • Bloody diarrhea may result from hemorrhoids, anal fissures, infections, IBD, ulcers, or cancer.

  • Bright red blood points to bleeding low in the digestive tract, while dark/tarry stools suggest bleeding higher up.

  • Treatment depends on the cause but always includes hydration and medical evaluation.

  • See a doctor immediately if bleeding is heavy, persistent, or accompanied by severe pain, fever, or dehydration.