Blood in stool can range from something relatively minor, like hemorrhoids, to serious conditions such as inflammatory bowel disease or cancer, so it should never be ignored, especially if it is new, recurrent, or heavy. If you notice blood plus symptoms like dizziness, severe pain, or large amounts of blood, that is an emergency and needs immediate medical care.

What “blood in stool” can look like

  • Bright red on toilet paper, on the stool, or in the toilet bowl (often lower bowel causes such as hemorrhoids or anal fissures).
  • Dark red or maroon mixed with stool (bleeding higher in the colon or small bowel).
  • Black, tar‑like, very foul‑smelling stool, called melena (often from bleeding higher up, such as stomach or duodenum ulcers).

Color alone is not enough to tell how serious it is, but it gives doctors important clues.

Common, often less serious causes

These are frequent reasons people see blood in their stool, especially if they are otherwise well:

  • Hemorrhoids
    • Swollen veins in the anus or rectum.
    • Usually cause bright red blood on toilet paper or coating the stool, sometimes with itching or discomfort when sitting or passing stool.
* Often linked with constipation, straining, pregnancy, or sitting on the toilet for a long time.
  • Anal fissures
    • Tiny tears in the skin of the anus, often from passing a large or hard stool.
* Typically cause sharp pain with bowel movements and a small amount of bright red blood on the stool or paper.
  • Gastroenteritis (stomach/intestinal infection)
    • Infection from viruses, bacteria, or parasites can inflame the gut and sometimes cause bloody diarrhea.
* Often comes with cramps, fever, nausea, and frequent loose stools.

Even when causes are “common,” a doctor should still confirm the diagnosis if blood appears more than once.

More serious possible causes

Some conditions need prompt evaluation because they can damage the bowel or cause significant blood loss over time:

  • Inflammatory bowel disease (IBD) – Crohn’s disease and ulcerative colitis
    • Long‑term inflammation of the digestive tract; often causes bloody diarrhea, abdominal pain, urgency to go, weight loss, and fatigue.
* Symptoms usually last weeks or longer and may come and go in flares.
  • Diverticular disease / diverticulitis
    • Small pouches in the wall of the colon that can bleed or become inflamed.
* May cause sudden, sometimes heavy rectal bleeding, and diverticulitis can cause fever and left‑sided abdominal pain.
  • Colon or rectal polyps and cancer
    • Polyps are growths in the colon; some are precancerous and can bleed slowly.
* Colorectal cancer can cause blood in stool (sometimes invisible), changes in bowel habits, weight loss, or anemia (tiredness, shortness of breath).

* This is one reason screening colonoscopies are recommended from middle age or earlier if there is a family history.
  • Peptic ulcers and upper GI causes
    • Ulcers in the stomach or duodenum can bleed and cause black, tarry stools; heavy bleeding can also cause vomiting blood.
* Often linked with infection (H. pylori), certain medications like NSAIDs, or other conditions.

There are also rarer causes (such as vascular malformations, certain childhood conditions, or severe inflammatory infections), but a clinician needs to sort these out based on age and symptoms.

When to worry and seek help

You should seek urgent or emergency care (same day, emergency department or ambulance) if:

  • You pass a large amount of blood or clots, or the water in the toilet turns visibly red.
  • You feel light‑headed, faint, unusually weak, sweaty, or your heart is racing.
  • You have severe or worsening abdominal pain, a rigid or very tender belly, or a high fever.
  • You have black, tarry stools, especially with vomiting blood or coffee‑ground‑like material.

You should see a doctor soon (within days) if:

  • Any new blood in your stool appears and is not clearly from a one‑off minor cause.
  • Blood continues over more than one or two bowel movements, even if it seems mild.
  • You are over about 40–50 years old, or have a family history of bowel cancer, and notice blood or a change in your bowel pattern.
  • You have ongoing diarrhea, mucus in stool, weight loss, or unexplained fatigue.

What doctors usually do

A clinician will decide what tests you need based on your age, symptoms, and risk factors.

Typical steps include:

  1. History and physical exam
    • Questions about how the blood looks, how often it appears, bowel habits, pain, weight changes, medications, and family history.
 * Examination of the abdomen and often a rectal exam to check for hemorrhoids, fissures, or masses.
  1. Basic tests
    • Blood tests to look for anemia, infection, or inflammation.
 * Stool tests for infection or tiny amounts of hidden blood.
  1. Endoscopy or imaging (if needed)
    • Colonoscopy or sigmoidoscopy to look directly at the colon and rectum and treat or biopsy anything abnormal.
 * Upper endoscopy (gastroscopy) if black stools or upper‑gut symptoms suggest bleeding higher up.

 * In some cases, CT scans or other imaging if bleeding is hard to localize.

Treatment then targets the cause: e.g., stool softeners and creams for hemorrhoids or fissures, antibiotics for certain infections, anti‑inflammatory or immune medications for IBD, or procedures/surgery for polyps, diverticular bleeding, or cancers.

Important: Any blood in your stool deserves medical attention, and online information cannot replace an in‑person assessment. If this is happening to you right now, especially with pain, dizziness, or heavy bleeding, seek urgent medical care.

Information gathered from public forums or data available on the internet and portrayed here.