Introduction
Bloody diarrhea can be alarming, especially when blood appears suddenly with frequent loose or watery bowel movements. While some causes are relatively minor, bloody diarrhea can also be a sign of an intestinal infection, inflammation, or gastrointestinal bleeding that requires prompt medical attention.
Diarrhea is generally defined as loose or watery stools occurring three or more times a day or more frequently than is normal for an individual. When blood is present, additional symptoms such as abdominal cramps, fever, vomiting, weakness, or dehydration may occur depending on the underlying cause.
Common causes include certain bacterial infections, inflammatory bowel disease, and other conditions affecting the digestive tract. Food poisoning is another important cause of bloody diarrhea, particularly when it develops with abdominal pain and fever.
Because blood in the stool can sometimes indicate significant gastrointestinal bleeding, it should not simply be ignored. This article explains the possible causes of bloody diarrhea, symptoms to watch for, how doctors diagnose it, treatment options, and when urgent medical care is needed.
What Is Bloody Diarrhea?
Bloody diarrhea means passing loose or watery stool that contains visible blood. The blood may appear bright red, dark red, or mixed throughout the stool.
The appearance of blood can sometimes provide clues about where bleeding is occurring, but color alone cannot establish the cause.
Bloody diarrhea may occur with:
- Frequent watery stools
- Abdominal cramps
- Abdominal pain
- Fever
- Nausea
- Vomiting
- Urgency to use the bathroom
- Mucus in the stool
- Weakness
- Dizziness
- Dehydration
Some infections can cause bloody stools along with fever and chills, while other conditions can produce blood because of inflammation or injury to the intestinal lining.
Is Bloody Diarrhea Serious?
It can be.
Blood in diarrhea is not something that should routinely be treated at home without determining the likely cause. NIDDK recommends seeking medical help promptly when stools contain red blood or pus, especially when diarrhea is accompanied by severe pain, dehydration, frequent vomiting, or other concerning symptoms.
The seriousness depends on factors such as:
- Amount of blood
- Duration of diarrhea
- Age
- Underlying health conditions
- Presence of fever
- Severity of abdominal pain
- Signs of dehydration
- Recent antibiotic use
- Recent travel
- Immune system status
Large amounts of blood, dizziness, fainting, weakness, rapid heartbeat, or signs of shock require emergency medical attention.
Common Causes of Bloody Diarrhea
1. Bacterial Infections
Certain bacterial infections are among the important causes of acute bloody diarrhea.
Bacteria can enter the digestive system through contaminated food or water. Foodborne infections may cause diarrhea, abdominal pain, vomiting, fever, and sometimes blood in the stool.
Depending on the organism involved, symptoms can range from mild to severe.
2. Food Poisoning
Food poisoning occurs when contaminated food or beverages contain harmful bacteria, viruses, parasites, toxins, or chemicals.
Bloody diarrhea can occur with some forms of food poisoning. Other symptoms may include:
- Stomach cramps
- Fever
- Vomiting
- Nausea
- Headache
- Weakness
Some foodborne illnesses resolve within several days, while others can cause serious complications and require medical treatment.
3. Inflammatory Bowel Disease
Inflammatory bowel disease, including ulcerative colitis and Crohn’s disease, can cause inflammation and damage within the digestive tract.
Ulcerative colitis particularly affects the colon and may cause:
- Bloody diarrhea
- Abdominal cramps
- Urgency
- Frequent bowel movements
- Mucus in the stool
Crohn’s disease can affect different parts of the digestive tract and may also cause diarrhea, abdominal pain, weight loss, and other symptoms.
People with recurrent or persistent bloody diarrhea should be evaluated for inflammatory bowel disease when appropriate.
4. Hemorrhoids
Hemorrhoids are swollen veins around the anus or lower rectum and can cause bright red blood.
However, hemorrhoids usually cause bleeding rather than true bloody diarrhea. If blood is mixed with frequent loose stools, another cause may need to be investigated.
It is therefore important not to automatically assume that hemorrhoids explain every episode of blood in the stool.
5. Anal Fissures
An anal fissure is a small tear in the skin around the anus. It can cause bright red bleeding, particularly during or after bowel movements.
Anal fissures are often associated with constipation and hard stools, but irritation from frequent diarrhea can also contribute to anal discomfort and skin damage.
6. Reduced Blood Flow to the Colon
Reduced blood flow to part of the colon, known as intestinal ischemia or ischemic colitis depending on the situation, can cause abdominal pain and bloody stools.
Sudden severe abdominal pain accompanied by bloody diarrhea can require urgent medical assessment.
7. Gastrointestinal Bleeding
Bleeding anywhere within the gastrointestinal tract can potentially appear in stool.
Lower gastrointestinal bleeding can result from conditions such as:
- Hemorrhoids
- Anal fissures
- Diverticular disease
- Colitis
- Polyps
- Colon or rectal cancer
Other digestive conditions, including ulcers and inflammatory disorders, can also cause gastrointestinal bleeding.
Symptoms That May Occur With Bloody Diarrhea
The symptoms accompanying bloody diarrhea often provide important information.
Abdominal Pain and Cramping
Abdominal cramps are common with infectious diarrhea and inflammatory conditions. Severe or worsening pain, however, requires medical evaluation.
Fever
Fever can occur when bloody diarrhea is caused by an infection or significant inflammation.
A high fever together with bloody diarrhea is particularly concerning and should be assessed by a healthcare professional.
Nausea and Vomiting
Vomiting may accompany food poisoning or gastrointestinal infections. Frequent vomiting can make dehydration happen more quickly.
Dehydration
Diarrhea causes the body to lose water and electrolytes.
Signs of dehydration include:
- Excessive thirst
- Dry mouth
- Dark urine
- Urinating less frequently
- Dizziness
- Weakness
- Fatigue
- Lightheadedness
Severe dehydration can become dangerous and requires prompt treatment.
Mucus in the Stool
Some intestinal infections and inflammatory conditions can cause mucus along with blood and diarrhea.
Weakness or Dizziness
Significant fluid loss or gastrointestinal bleeding can cause weakness, dizziness, or fainting. These symptoms should be taken seriously.
Bloody Diarrhea in Children
Bloody diarrhea can be particularly concerning in infants and children because they can become dehydrated quickly.
Parents and caregivers should seek medical advice promptly if a child develops bloody or black stools, frequent diarrhea, severe abdominal pain, repeated vomiting, fever, or signs of dehydration.
Do not give a child anti-diarrheal medication without medical advice.
Bloody Diarrhea During Pregnancy
Pregnant people with bloody diarrhea should contact a healthcare professional rather than assuming the problem is a routine stomach infection.
Dehydration can be particularly problematic, and some infections may require specific treatment.
Pregnancy, older age, and a weakened immune system are among the situations in which diarrhea can pose greater health risks.
How Is Bloody Diarrhea Diagnosed?
Doctors usually begin with a detailed medical history and physical examination.
They may ask:
- When did the diarrhea begin?
- How many bowel movements are occurring each day?
- How much blood is present?
- Is the blood bright red or dark?
- Is there abdominal pain?
- Is there fever?
- Have you recently traveled?
- Did you eat potentially contaminated food?
- Have you recently taken antibiotics?
- Are other people around you sick?
- Do you have a history of digestive disease?
- Are you taking medications that may increase bleeding risk?
NIDDK notes that medical history, physical examination, and selected tests can help identify the cause of diarrhea.
Stool Tests
A stool sample may be examined for infectious organisms or other abnormalities.
This can be especially useful when bloody diarrhea suggests an infectious cause.
Blood Tests
Blood tests may help identify:
- Anemia
- Signs of inflammation
- Infection
- Dehydration
- Electrolyte abnormalities
Endoscopy or Colonoscopy
If doctors suspect inflammatory bowel disease, persistent gastrointestinal bleeding, or another structural problem, they may recommend endoscopic evaluation.
A colonoscopy allows the doctor to examine the lining of the colon and, when necessary, take tissue samples.
Gastrointestinal bleeding can sometimes be diagnosed and treated during an endoscopic procedure.
Treatment for Bloody Diarrhea
Treatment depends entirely on the underlying cause.
Focus on Hydration
Replacing lost fluids is one of the most important priorities when diarrhea occurs.
Oral rehydration solutions can provide water and electrolytes. People with significant dehydration may require medical treatment, including intravenous fluids.
Treating an Infection
Some bacterial or parasitic infections may require specific medication.
However, antibiotics are not appropriate for every case of bloody diarrhea. The correct treatment depends on the organism and clinical situation.
NIDDK specifically advises people with bloody diarrhea or fever not to use over-the-counter anti-diarrheal medicines without medical guidance because these symptoms can indicate bacterial or parasitic infection.
Treatment for Inflammatory Bowel Disease
If bloody diarrhea is caused by ulcerative colitis or Crohn’s disease, treatment may involve medications that reduce inflammation and control the immune response.
The treatment plan depends on the type and severity of the disease.
Treatment of Gastrointestinal Bleeding
If significant gastrointestinal bleeding is identified, doctors first determine its location and cause.
Depending on the situation, treatment may include medication, endoscopic procedures, surgery, blood transfusion, or other interventions.
Should You Take Anti-Diarrhea Medicine?
People should be cautious about taking medications such as loperamide when they have bloody diarrhea.
Anti-diarrheal medications may be inappropriate in certain infections and can potentially make some situations worse. NIDDK recommends against over-the-counter anti-diarrheal medicines for people with bloody stools or fever unless directed by a healthcare professional.
Do not self-treat bloody diarrhea simply to stop bowel movements without understanding why the bleeding is occurring.
What Should You Eat and Drink?
Maintaining hydration is more important than forcing yourself to eat a large meal.
Depending on how you feel, you may tolerate simple foods and gradually return to your normal diet as your appetite improves.
Helpful measures may include:
- Drinking water regularly
- Using oral rehydration solutions
- Eating small portions
- Choosing foods that are easy to tolerate
- Avoiding excessive alcohol
- Avoiding foods that clearly worsen symptoms
If vomiting prevents you from keeping fluids down, seek medical advice.
What Should You Avoid During Bloody Diarrhea?
Until you have medical advice, avoid unnecessary use of anti-diarrheal medication when blood or fever is present.
You should also avoid assuming that antibiotics are always necessary. Some infections are viral, and inappropriate antibiotic use can cause side effects or contribute to antibiotic resistance.
If you recently took antibiotics and developed significant diarrhea, tell your healthcare provider because antibiotic-associated diarrhea can have specific causes and treatment considerations.
When Is Bloody Diarrhea an Emergency?
Seek emergency medical care if bloody diarrhea is accompanied by:
- A large amount of blood
- Fainting
- Severe dizziness
- Confusion
- Rapid heartbeat
- Severe weakness
- Pale, cold, clammy skin
- Severe abdominal pain
- Signs of shock
- Inability to keep fluids down
- Severe dehydration
Acute gastrointestinal bleeding can become life-threatening when blood loss is substantial. Symptoms of shock require immediate emergency treatment.
Adults should also seek prompt medical attention for bloody stools, severe abdominal or rectal pain, dehydration, or diarrhea that persists beyond two days.
Can Bloody Diarrhea Be Prevented?
Not every cause can be prevented, but several habits can lower the risk of infectious diarrhea.
Practice Food Safety
Wash hands before preparing food and after using the bathroom. Cook meat thoroughly and avoid foods that have been improperly stored.
Drink Safe Water
Use safe drinking water, particularly when traveling.
Wash Produce
Wash fruits and vegetables appropriately before eating.
Prevent the Spread of Infection
If someone in the household has infectious diarrhea, careful hand hygiene and appropriate cleaning can reduce transmission.
Use Antibiotics Responsibly
Only take antibiotics when prescribed and use them exactly as directed.
Bloody Diarrhea After Travel
Travel can expose people to unfamiliar bacteria, viruses, and parasites through contaminated food or water.
Tell your healthcare provider about recent international travel if bloody diarrhea develops afterward. Travel history can help doctors narrow down potential causes and choose appropriate testing.
Bloody Diarrhea After Antibiotics
Diarrhea occurring after antibiotic treatment deserves attention because antibiotics can disturb the normal balance of bacteria in the intestine.
If bloody diarrhea develops during or after antibiotic use, contact a healthcare professional rather than automatically taking an anti-diarrheal medicine.
Provide the doctor with information about:
- The antibiotic name
- Dose
- When treatment started
- When diarrhea began
- Number of bowel movements
- Presence of blood or mucus
- Fever or abdominal pain
When to See a Doctor for Bloody Diarrhea
Even if the bleeding appears small, it is sensible to discuss bloody diarrhea with a healthcare professional.
Prompt evaluation is particularly important when:
- Blood continues to appear
- Diarrhea becomes frequent
- You develop fever
- You have significant abdominal pain
- You feel weak or dizzy
- You are becoming dehydrated
- You recently traveled
- You recently took antibiotics
- You have inflammatory bowel disease
- You have a weakened immune system
- You are pregnant
- You are an older adult
Blood in stool can have many causes, so proper evaluation is more useful than trying to identify the cause from appearance alone.
Conclusion
Bloody diarrhea is a symptom rather than a disease, and its causes range from intestinal infections and food poisoning to inflammatory bowel disease and gastrointestinal bleeding. Because some causes can become serious, blood in diarrhea should not be ignored.
Treatment depends on the underlying cause. Staying hydrated is important, but people with bloody diarrhea or fever should not routinely use over-the-counter anti-diarrheal medicines without medical advice.
Seek urgent medical attention if bleeding is heavy or accompanied by severe abdominal pain, dizziness, fainting, confusion, rapid heartbeat, or signs of shock.
The good news is that many causes of bloody diarrhea can be diagnosed and treated effectively. Prompt medical evaluation can help identify the cause, prevent dehydration and complications, and ensure that appropriate treatment is started.
FAQs About Bloody Diarrhea
1. What causes bloody diarrhea?
Bloody diarrhea can be caused by intestinal infections, food poisoning, inflammatory bowel disease, colitis, reduced blood flow to the intestine, and other forms of gastrointestinal bleeding.
2. Is bloody diarrhea an emergency?
It can be. Heavy bleeding, severe abdominal pain, fainting, dizziness, weakness, confusion, rapid heartbeat, or signs of shock require emergency medical attention.
3. Can food poisoning cause bloody diarrhea?
Yes. Some bacterial and other foodborne infections can cause bloody diarrhea along with abdominal pain, fever, nausea, or vomiting.
4. Should I take Imodium for bloody diarrhea?
Do not take an over-the-counter anti-diarrheal such as loperamide without medical advice when you have bloody diarrhea, particularly if you also have a fever. Some infections can become more problematic when bowel movement-slowing medicines are used.
5. Can dehydration happen with bloody diarrhea?
Yes. Frequent diarrhea can cause substantial loss of water and electrolytes. Excessive thirst, dry mouth, dark urine, reduced urination, dizziness, and weakness can indicate dehydration.
6. Can hemorrhoids cause bloody diarrhea?
Hemorrhoids can cause bright red rectal bleeding, but they do not usually explain true diarrhea with blood mixed into the stool. Persistent bloody diarrhea should be evaluated rather than automatically attributed to hemorrhoids.
7. Can stress cause bloody diarrhea?
Stress can affect digestive function and may worsen some gastrointestinal conditions, but visible blood in diarrhea should not simply be blamed on stress. An underlying cause should be considered.
8. When should I see a doctor for bloody diarrhea?
You should seek prompt medical care for bloody stools, especially when accompanied by fever, severe abdominal pain, dehydration, frequent vomiting, weakness, or persistent diarrhea.
9. Can antibiotics cause bloody diarrhea?
Antibiotics can cause diarrhea and may alter intestinal bacteria. If significant or bloody diarrhea develops during or after antibiotic treatment, contact a healthcare professional for evaluation.
10. How is bloody diarrhea diagnosed?
Doctors may use medical history, physical examination, stool tests, blood tests, and sometimes endoscopy or colonoscopy to determine the cause. The choice of testing depends on the symptoms and suspected condition.
