10 Causes of Bloody Diarrhea & Treatments

When noticing bloody stool, the most common causes derive from hemorrhoids or anal fissures. Bloody diarrhea, however is generally not normal and can be caused by an intestinal infections such as E. Coli, food poisoning, or an intestinal parasite. Read below for more information on causes and when to seek emergency treatment.

Common bloody diarrhea symptoms

Although this is probably not a favored topic of discussion, it is not uncommon to notice blood even a small amount of bright red blood in your stool from time to time. Typically, this is caused by conditions such as hemorrhoids (enlarged blood vessels in the rectum or anus) or anal fissures (tears or cracks in the tissue lining the anus or rectum).

Diarrhea is also common condition experienced by just about everyone several times during their lives. Most of the time, diarrhea occurs due to infection or from foods that disagree with you. Bloody diarrhea, on the other hand, is not so common or normal, and requires professional medical care.

Common accompanying symptoms of bloody diarrhea

Bloody diarrhea may or may not be accompanied by:

  • Nausea or vomiting
  • Fever and chills
  • Stomach pain
  • Fatigue
  • Severe anemia
  • Dizziness or weakness
  • Shortness of breath
  • Chest pain
  • Headache

In most occurrences, bloody diarrhea is a sign of intestinal infection; sometimes, it can be an indication of a more serious condition, such as cancer or a vascular problem with your bowels. Lets look at the infections and non-infectious causes of bloody diarrhea.

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What causes blood in diarrhea?


Bloody diarrhea due to infection may be caused by the following.

  • Bacterial infections
  • Enterohemorrhagic Escherichia coli (EHEC): There are many strains of the bacteria E. coli. Some strains of E. coli normally live in your intestines and do not cause illness. Some strains of E. coli can release shiga toxin and make you very sick with stomach pain, bloody diarrhea and even kidney failure. Strains include shigella, campylobacter, and salmonella.
  • Viral infections: These are probably the most common infections to give you bloody stools and many viruses are capable of doing this, like Norovirus, Rotavirus, and Adenovirus.
  • Parasitic infections: Infections with parasites like Entamoeba histolytica and Giardia Lamblia (common in hikers who unknowingly drink water with beaver poop in it!) can lead to bloody diarrhea.

Serious non-infectious conditions

Serious conditions that can result in bloody diarrhea include the following.

  • Ischemic colitis: This is a condition in which the blood flow to the large intestine is restricted. This may cause damage to your colon damage severe enough to cause bloody diarrhea and even necrosis (death) of all or part of your colon. This is usually associated with severe abdominal pain and often occurs in people with a history of vascular disease elsewhere in the body.
  • Inflammatory Bowel Disease: Bloody diarrhea that is a result of a chronic disease process, such as inflammatory bowel disease (IBD), often lasts weeks or months and is associated with weight loss and feeling unwell. This can also cause you to lose blood and become anemic. Crohn's Disease and Ulcerative Colitis are the two most common types of IBD and both require the specialized care of a doctor called a gastroenterologist.
  • Colon cancer: Colon cancer can cause both diarrhea (which may or may not be bloody) and constipation. Other symptoms associated with colon cancer include a change in bowel habits, stomach pain, fatigue, weight loss and anemia.

Anal and rectal causes of bloody diarrhea

Neither of these conditions are life-threatening, but both of these need medical care so you can feel better and not make these worse.

  • Hemorrhoids: These are a common cause of blood on the toilet paper and on the outside of the stool, though they can also cause blood to be present in loose stools and diarrhea. Usually you will have pain, itching or even feel these near the anus.
  • Anal fissures: These can bleed and are usually associated with severe pain with bowel movements or pain after a bowel movement. This is a crack or tears in the anus and it can bleed, lead to blood on the toilet paper and in the stool.

Food poisoning

Food poisoning, also called foodborne illness or "stomach flu," is an acute infection of the digestive tract from food contaminated with bacteria, viruses, parasites, or other toxins. It actually has no relation to influenza.

Any food can become contaminated if not prepared under clean conditions, cooked thoroughly, or stored at cold temperatures. Meat, fish, dairy products, and fresh fruits and vegetables are some of the most easily contaminated foods.

Symptoms include nausea, vomiting, diarrhea, and abdominal pain, and sometimes fever and chills.

Most people recover on their own with supportive care, meaning rest, fluids, and over-the-counter pain relievers and fever reducers.

However, dehydration can result if the vomiting and/or diarrhea are not controlled and IV fluids may be needed.

If there is also blurred vision, dizziness, or paralysis, the nervous system may be affected due to botulism. This is a medical emergency. Take the patient to the emergency room or call 9-1-1.

Proper food preparation and storage, along with frequent and thorough handwashing, is the best prevention.

Rarity: Common

Top Symptoms: nausea, abdominal pain (stomach ache), headache, abdominal cramps (stomach cramps), dizziness

Symptoms that never occur with food poisoning: severe fever, being severely ill, bloody diarrhea

Urgency: Self-treatment

E. coli infection

E. coli are a large and diverse group of bacteria that can often be found in the intestines of healthy humans and animals. E. coli comes in a variety of strains. Although most strains are harmless, a few types can make people sick with diarrhea, as well as UTIs and respiratory illnesse...

Intestinal infection with ameba parasite

Visiting or living in places with poor sanitation can lead to parasite infections that can cause long-lasting diarrhea and stomach pain.

Rarity: Rare

Top Symptoms: nausea, loss of appetite, diarrhea, constipation, general abdominal pain

Urgency: Primary care doctor

Diarrhea caused by a bacteria called vibrio

The Vibrio genus of bacteria causes nausea, vomiting, and diarrhea that can be very serious. Vibrio parahaemolyticus and Vibrio vulnificus are two of the species that cause this illness, which is also called vibriosis.

The primary risk factor is eating raw or undercooked seafood, especially oysters from any coastal waters and from the Gulf of Mexico in particular. People with weakened immune systems or liver disease are especially vulnerable to this infection.

Symptoms include fever, vomiting, and diarrhea, sometimes with mental confusion. These symptoms in a person who has recently eaten raw seafood, or has been swimming in ocean or bay water, are considered a medical emergency. Take the patient to the emergency room or call 9-1-1.

Some types of Vibrio-caused illness can worsen very quickly and lead to dehydration and septicemia, which can be life-threatening.

Diagnosis is made through patient history, physical examination, and lab tests on blood, urine, and stool samples.

Treatment will usually involve hospitalization for intravenous fluids, antibiotics, and supportive care.

Rarity: Rare

Top Symptoms: diarrhea, nausea, stomach bloating, headache, abdominal cramps (stomach cramps)

Symptoms that always occur with diarrhea caused by a bacteria called vibrio: diarrhea

Urgency: Self-treatment

Campylobacter small intestine infection

Infection with the Campylobacter bacterium is one of the leading causes of acute diarrhea worldwide. The risk for this infection is increased in people with HIV/AIDS.

Rarity: Rare

Top Symptoms: diarrhea, abdominal cramps (stomach cramps), general abdominal pain, fever, severe diarrhea

Symptoms that always occur with campylobacter small intestine infection: diarrhea

Urgency: Primary care doctor

Ulcerative colitis

Ulcerative colitis is a chronic, long-term inflammatory disease of the gastrointestinal tract, specifically involving ulcers and sores of the large intestine (colon) and the rectum. Ulcerative colitis often begins gradually and worsens over time with periods of remission interspers...

New onset crohn's disease

Crohn's disease is an inflammation of the bowel. It is caused by a faulty immune system response which makes the body attack the lining of the intestines.

The disease usually appears before age thirty and can affect anyone. Those with a family history may be most susceptible. Smoking is a known risk factor.

Aggravating factors include stress, poor diet, and nonsteroidal anti-inflammatory drugs such as ibuprofen and aspirin.

Early symptoms usually develop gradually, but can appear suddenly. These include fatigue, loss of appetite, fever, mouth sores, diarrhea, abdominal pain, and blood in stool.

Untreated Crohn's disease can cause ulcers throughout the digestive tract as well as bowel obstruction, malnutrition, and deteriorating general health.

Diagnosis is made through blood test and stool sample test. Colonoscopy, CT scan, MRI, endoscopy, and/or enteroscopy may also be used.

Crohn's disease cannot be cured, but can be managed through reducing the inflammation. Antibiotics, corticosteroids, and immune system suppressors may be tried. Excellent nutrition, vitamin supplements, smoking cessation, and reduction in stress can be helpful.

Rarity: Rare

Top Symptoms: fatigue, stomach bloating, loss of appetite, constipation, abdominal cramps (stomach cramps)

Urgency: Primary care doctor

Bacterial infection caused by clostridium difficile

Antibiotic use can disrupt the normal microorganisms that inhabit the human digestive tract, and a bacterium called Clostridium difficile can grow out of control in the intestines. Though relatively rare compared to other bacterial infections, C. Difficile is one of the leading causes of infectious diarrhea in the United States.

Rarity: Rare

Top Symptoms: abdominal pain (stomach ache), abdominal cramps (stomach cramps), being severely ill, fever, watery diarrhea

Urgency: In-person visit

Colon damage from impaired blood flow

Acute intestinal ischemia means that the blood flow to the large and/or small intestines has been cut off. It is also called acute mesenteric ischemia, or AMI.

The ischemia is caused by blockage in one of the arteries leading into the abdomen, usually due to atherosclerosis (plaque) or a blood clot.

Most susceptible are those with very high or low blood pressure; heart disease; or using illegal drugs such as cocaine or methamphetamine.

Symptoms include sudden, severe pain in one area of the abdomen; nausea and vomiting; and repeated, urgent bowel movements, often with blood.

Acute intestinal ischemia is a life-threatening medical emergency. If it is suspected, take the patient to the emergency room or call 9-1-1.

Diagnosis is made through arteriogram, which involves injecting dye into the abdominal arteries under x-ray in order to find the exact location of the blockage.

Treatment involves "clot-busting" drugs to destroy a clot, or emergency surgery to remove whatever is causing the blockage and possibly some of the damaged intestine as well.

Rarity: Rare

Top Symptoms: abdominal pain (stomach ache), nausea, loss of appetite, diarrhea, being severely ill

Urgency: Hospital emergency room

Hemolytic uremic syndrome

Hemolytic Uremic Syndrome, or HUS, is kidney damage resulting from the abnormal destruction of red blood cells. These dead cells block the filtering system within the kidneys, leading to kidney failure.

Diarrhea caused by infection with E. coli bacteria is the most common cause of this red blood cell breakdown. Other, less common, causes are some medications and other infections. It can be a rare complication of pregnancy.

E. coli is spread through contaminated food or water; by swimming in water contaminated with feces; and by close contact with an infected person.

Young children are most susceptible, though anyone can be affected.

Symptoms include bloody diarrhea; blood in the urine; bleeding from nose and mouth; little or no urine output; abdominal pain; vomiting; fever; confusion; and seizures.

HUS is a medical emergency. It can lead to kidney failure, stroke, and coma. Take the patient to the emergency room or call 9-1-1.

Diagnosis is made through blood, urine, and/or stool sample tests.

Treatment requires hospitalization for IV fluids, blood and plasma transfusions, and sometimes dialysis.

Rarity: Ultra rare

Top Symptoms: abdominal pain (stomach ache), fatigue, nausea, diarrhea, being severely ill

Symptoms that always occur with hemolytic uremic syndrome: being severely ill

Urgency: Hospital emergency room

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When and how to treat bloody diarrhea

When bloody diarrhea is an emergency

You should seek immediate care for bloody diarrhea if:

  • You have had it for more than 24 hours
  • You have diarrhea that is dark red or black
  • You have severe abdominal pain
  • You have signs of dehydration: Dry mouth, dizziness, confusion, muscle cramping, and excessive thirst
  • You have a fever: One that is >100.4
  • You are over 65 years old
  • You are pregnant
  • You are currently or have recently finished taking a course of antibiotics

How to begin addressing your bloody diarrhea

The treatment of bloody diarrhea requires addressing the underlying cause.

  • Avoid using anti-diarrheal medications: such as loperamide or bismuth salicylate and diphenoxylate. These medications can complicate EHEC infections.
  • Stop taking any antibiotics
  • Avoid NSAIDs and other substances: Non-steroidal anti-inflammatory drugs such as ibuprofen (Advil, Motrin), smoking, alcohol, aspirin, anticoagulants, and anti-platelet agents should be avoided.

Other at-home treatments for diarrhea

As with any diarrhea, it is important to stay well-hydrated and well-nourished. It is equally important to replace electrolytes, especially sodium and potassium and this can be done with commercial sports beverages, bullion, and fluids containing sodium and potassium.

FAQs about bloody diarrhea

Here are some frequently asked questions about bloody diarrhea.

What foods can cause blood in stool?

Only foods that contain a large amount of blood (blood sausage, blood pudding), foods that contain large amounts of heme (or the chemical in blood that holds oxygen), or foods that cause laceration to the bowel cause blood in the stool. Sharp items that are not food glass, stones, metal can lacerate the bowel causing blood in the stool. Other foods can cause ulcers in the GI tract. Foods that are very high in acid, or foods that cause "metaplasia" or changing of the structure of cells can over the long term, can lead to bleeding.

Can constipation cause blood in stool?

Constipation by itself does not cause blood in the stool. However, passing a particularly large stool may cause an anal fissure which usually presents with bright red blood on the tissue or in the toilet. If you have a history of hemorrhoids, passing hard stool can cause rupture of a hemorrhoid and dark red blood either on the stool or in the toilet. Finally, long term constipation can cause outpouchings of the intestines (diverticulosis) exposing blood vessels and causing dark red blood in the stool.

Can hemorrhoids cause bleeding in the stool?

Yes, hemorrhoids can cause bleeding either in the bowel, streaked on the feces, or on the toilet paper. Bleeding from hemorrhoids is usually painless and often happens sometime after a bowel movement but can be unprovoked. The blood may drip into the toilet and tinge the color of the water. Bleeding can also occur in large amounts which is worsened by straining.

Can certain antibiotics cause bloody diarrhea?

No. However, some antibiotics can alter the color of feces. Antibiotics do not affect the lining of the gut in such a way as to cause rupture. They may, however, cause cramping or bloating (from a lack gut mobility) or diarrhea from an increase in mobility. However, antibiotics can cause a form of infectious diarrhea, C. difficile, that infrequently may be associated with bleeding.

When should you see a doctor for bloody stool?

You should see a doctor if you are concerned about blood in your stool. You should visit the emergency room if there is a large amount of blood, if the blood is dark red or looks like coffee grounds or dark red sludge, or if you experience any lightheadedness, dizziness, or cold and clammy sensation or vomit blood.

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Take a thorough self-assessment on what you may have

Questions your doctor may ask about bloody diarrhea

  • Any fever today or during the last week?
  • Have you experienced any nausea?
  • Have you been feeling more tired than usual, lethargic or fatigued despite sleeping a normal amount?
  • Have you lost your appetite recently?

Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.

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