Blood in Stool: Causes, Symptoms & When to See a Doctor

What Does Blood in Stool Look Like?

Blood in stool can appear in several different forms: bright red blood on the surface of stool or toilet paper, dark red or maroon blood mixed with stool, visible blood in the toilet bowl, black tarry stool (melena), or mucus mixed with blood. The appearance provides important clues about the source of bleeding.

The appearance of blood in your stool is one of the most important pieces of information for determining the source and potential cause of bleeding. Healthcare providers use this information to guide their diagnostic approach and determine the urgency of investigation. Understanding what to look for can help you provide accurate information to your doctor.

Blood in stool can manifest in several distinct ways, and each pattern suggests a different potential source of bleeding within the gastrointestinal tract. The gastrointestinal tract is essentially a long tube running from the mouth to the anus, and bleeding can occur at any point along this path. Generally speaking, the color and consistency of blood you see relates to how far the blood has traveled through the digestive system before reaching the toilet.

The longer blood remains in the digestive system, the more time digestive enzymes and bacteria have to break it down, which changes its appearance from bright red to dark red, and eventually to black. This is why bleeding from the stomach typically produces black, tarry stool rather than bright red blood.

Bright Red Blood (Hematochezia)

Bright red blood is the most commonly noticed form of rectal bleeding and typically indicates that the bleeding source is located in the lower gastrointestinal tract - specifically the rectum, anus, or lower portion of the colon. This blood has not had time to be digested, so it retains its fresh, red appearance. You might notice bright red blood on the toilet paper when you wipe, on the surface of your stool, dripping into the toilet bowl, or streaked on the outside of formed stool.

The most frequent causes of bright red rectal bleeding include hemorrhoids (swollen blood vessels in the rectum or anus), anal fissures (small tears in the lining of the anus), and occasionally rectal polyps or tumors. In many cases, the blood appears separate from the stool rather than mixed within it, which suggests a source very close to the anal opening.

Dark Red or Maroon Blood

When blood appears dark red, maroon, or burgundy in color, it typically suggests bleeding from higher up in the colon or from the small intestine. This blood has had more time to be partially digested during its transit through the intestines, causing it to darken. Dark red blood is often mixed throughout the stool rather than appearing on the surface, which indicates it entered the digestive tract before the stool was fully formed.

Causes of dark red or maroon blood include diverticular bleeding (bleeding from small pouches in the colon wall), inflammatory bowel disease (Crohn's disease or ulcerative colitis), colon polyps, colorectal cancer, and arteriovenous malformations (abnormal blood vessel formations in the colon). This type of bleeding often warrants more urgent investigation than isolated bright red bleeding.

Black Tarry Stool (Melena)

Black, tarry, sticky stool with a distinctive foul odor is called melena and indicates bleeding from the upper gastrointestinal tract - the esophagus, stomach, or duodenum (first part of the small intestine). The black color occurs because blood has been exposed to stomach acid and digestive enzymes over several hours, which breaks down the hemoglobin in blood and converts it to a compound called hematin, which is black.

Melena is always a significant finding that requires prompt medical evaluation. Common causes include peptic ulcers (stomach or duodenal ulcers), gastritis (inflammation of the stomach lining), esophageal varices (enlarged veins in the esophagus, often related to liver disease), and Mallory-Weiss tears (tears in the esophageal lining from severe vomiting). Even a small amount of blood from the upper GI tract can cause several days of black stool.

Blood with Mucus

When blood appears mixed with mucus in the stool, it often suggests inflammation or infection in the colon. The mucus is produced by the intestinal lining as a protective response. This combination is commonly seen in inflammatory bowel diseases such as ulcerative colitis and Crohn's disease, infectious colitis (bacterial or parasitic infections), and sometimes in colorectal cancer.

When Should You See a Doctor for Blood in Stool?

You should see a doctor if you notice blood in your stool, even if it only occurs once. Seek immediate emergency care if you experience heavy bleeding, severe abdominal pain, dizziness or lightheadedness, signs of shock (pale skin, rapid heartbeat, confusion), or black tarry stool. Most cases are not emergencies, but all rectal bleeding should be evaluated by a healthcare provider.

The presence of blood in your stool is always worth investigating, regardless of how minor it may seem. While the vast majority of rectal bleeding cases turn out to be caused by benign conditions like hemorrhoids or anal fissures, the same symptom can also be the first sign of more serious conditions including colorectal cancer. The only way to know for certain what is causing your bleeding is through proper medical evaluation.

Many people delay seeking medical attention for rectal bleeding because they assume it must be hemorrhoids, feel embarrassed about the symptoms, or hope the bleeding will resolve on its own. While these feelings are understandable, delaying evaluation can mean missing an opportunity for early diagnosis of treatable conditions. Colorectal cancer, for example, has a much better prognosis when detected early.

The urgency of seeking care depends on the amount and characteristics of bleeding, associated symptoms, and your individual risk factors. Understanding when to seek routine care versus emergency care can help you respond appropriately.

Contact Your Doctor (Non-Urgent)

You should contact your primary care physician or a gastroenterologist within a few days if you notice blood when you have a bowel movement and don't know the cause, even if it has only happened once. Other reasons to schedule an appointment include small amounts of bright red blood on toilet paper or stool surface, rectal bleeding that comes and goes over time, changes in your bowel habits lasting more than a few days, and bleeding that you suspect is from hemorrhoids but hasn't been confirmed by a doctor.

While these situations are not emergencies, they still require professional evaluation to determine the cause and rule out serious conditions.

Don't Let Embarrassment Delay Care

Many people feel embarrassed or uncomfortable about discussing rectal symptoms or undergoing examination of the anal area. It's important to remember that healthcare providers perform these examinations routinely - this is simply a normal part of their job, and they approach it professionally and respectfully. The potential consequences of delaying diagnosis far outweigh any temporary discomfort from the examination.

If you feel anxious about the appointment, it may help to remember that you can request a same-gender provider if that makes you more comfortable, bring a trusted person for support, write down your symptoms beforehand so you don't forget anything, and ask questions about any procedures before they're performed.

What Causes Blood in Stool in Adults?

The most common causes of blood in stool in adults are hemorrhoids and anal fissures. Other causes include inflammatory bowel disease (Crohn's disease, ulcerative colitis), diverticular disease, colon polyps, colorectal cancer, peptic ulcers, gastritis, certain medications, and infections. The cause can often be suggested by the blood's appearance and associated symptoms.

Rectal bleeding can originate from any point along the gastrointestinal tract, from the esophagus to the anus. The underlying causes range from very common and benign conditions to rare and serious diseases. Understanding the potential causes can help you have an informed discussion with your healthcare provider, but remember that only proper medical evaluation can determine the actual cause of your symptoms.

The causes of rectal bleeding can be broadly categorized based on where in the GI tract the bleeding originates. Lower GI bleeding (from the colon, rectum, and anus) typically produces bright red blood, while upper GI bleeding (from the esophagus, stomach, and duodenum) usually produces black tarry stool.

Hemorrhoids

Hemorrhoids are the most common cause of rectal bleeding in adults, affecting approximately half of all people over age 50 at some point. Hemorrhoids are swollen blood vessels located in the rectum (internal hemorrhoids) or around the anal opening (external hemorrhoids). They develop when increased pressure in the rectal veins causes them to stretch and bulge.

Internal hemorrhoids typically cause painless bleeding - you may notice bright red blood on the toilet paper, on the surface of stool, or dripping into the toilet bowl. They can also cause itching, discomfort, and a feeling of incomplete bowel movement. External hemorrhoids may cause pain, especially if a blood clot forms within them (thrombosed hemorrhoid).

Risk factors for hemorrhoids include chronic constipation or straining during bowel movements, sitting on the toilet for extended periods, chronic diarrhea, pregnancy, obesity, low-fiber diet, heavy lifting, and increasing age. While hemorrhoids are common and usually not dangerous, they should still be confirmed by a doctor rather than self-diagnosed.

Anal Fissures

An anal fissure is a small tear or crack in the lining of the anal canal, often caused by passing hard or large stools. Anal fissures are extremely common and are the second most frequent cause of rectal bleeding after hemorrhoids. They cause bright red blood on the stool surface or toilet paper, typically accompanied by sharp pain during bowel movements.

The pain from an anal fissure is often described as feeling like passing broken glass and may persist for minutes to hours after the bowel movement. This pain can create a cycle where fear of pain causes people to avoid bowel movements, leading to harder stools that make the fissure worse.

Most acute anal fissures heal within a few weeks with conservative treatment including high-fiber diet, adequate hydration, warm sitz baths, and topical treatments. Chronic fissures that don't heal may require additional treatment.

Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) includes two main conditions: ulcerative colitis and Crohn's disease. Both involve chronic inflammation of the gastrointestinal tract and can cause blood in the stool. Ulcerative colitis affects only the colon and rectum, causing continuous inflammation of the inner lining. Crohn's disease can affect any part of the GI tract and involves patchy, deeper inflammation.

In addition to bloody stool (often mixed with mucus), IBD typically causes abdominal pain, cramping, urgent bowel movements, chronic diarrhea, fatigue, unintentional weight loss, and fever during flares. These conditions are lifelong but can be managed with medication and, in some cases, surgery.

Diverticular Disease

Diverticula are small pouches that form in the walls of the colon, most commonly in the sigmoid colon (the lower left portion). Diverticulosis (having diverticula) is very common, affecting more than half of people over age 60. Most people with diverticulosis have no symptoms.

However, diverticular bleeding can occur when a blood vessel within or adjacent to a diverticulum erodes and bleeds. This typically causes sudden, painless, large-volume bleeding that is often dark red or maroon in color. While diverticular bleeding can be dramatic and frightening, it usually stops on its own. However, it requires medical evaluation and sometimes hospitalization.

Colorectal Polyps and Cancer

Colon polyps are growths that form on the inner lining of the colon. Most polyps are benign, but some types (particularly adenomatous polyps) can become cancerous over time. Polyps often cause no symptoms, which is why screening colonoscopy is so important - it can detect and remove polyps before they become cancerous.

When polyps or colorectal cancer do cause symptoms, these may include blood in the stool (which may be visible or invisible to the naked eye), changes in bowel habits such as persistent diarrhea or constipation, change in stool caliber (narrower than usual), abdominal discomfort, unexplained weight loss, and fatigue from chronic blood loss causing anemia.

Peptic Ulcers and Gastritis

Peptic ulcers are open sores that develop on the inner lining of the stomach or duodenum. Gastritis is inflammation of the stomach lining. Both conditions can cause bleeding into the digestive tract, which typically manifests as black, tarry stool (melena) rather than bright red blood, because the blood is digested as it passes through the GI tract.

Common causes of peptic ulcers and gastritis include Helicobacter pylori infection, regular use of NSAIDs (nonsteroidal anti-inflammatory drugs like ibuprofen, aspirin, and naproxen), excessive alcohol consumption, and severe stress (such as from major illness or injury).

Medications

Several types of medications can cause or contribute to gastrointestinal bleeding:

• NSAIDs: Ibuprofen, aspirin, naproxen, and similar drugs can irritate the stomach lining and interfere with the blood's clotting ability
• Blood thinners: Anticoagulants (warfarin, heparin, direct oral anticoagulants) and antiplatelet medications increase bleeding risk
• Corticosteroids: Long-term use can increase risk of gastric ulcers

If you take any of these medications and notice blood in your stool, inform your doctor - but do not stop taking prescribed medications without medical guidance.

Infections

Certain infections of the gastrointestinal tract can cause bloody diarrhea. These include bacterial infections such as Campylobacter, Salmonella, Shigella, and E. coli (including the dangerous EHEC/O157:H7 strain), parasitic infections like Entamoeba histolytica, and viral gastroenteritis (though this more commonly causes non-bloody diarrhea). Bloody diarrhea with fever should prompt medical evaluation.

How Is Blood in Stool Diagnosed?

Diagnosis of blood in stool involves a medical history review, physical examination including digital rectal examination, and diagnostic tests. Common tests include proctoscopy/sigmoidoscopy (examining the lower bowel), colonoscopy (complete colon examination), blood tests to check for anemia, stool tests, and sometimes imaging studies like CT scan. The specific tests depend on your symptoms, age, and risk factors.

When you see a doctor for blood in your stool, they will work to identify the source and cause of bleeding through a systematic approach. This typically begins with gathering information about your symptoms and medical history, progresses to physical examination, and then to diagnostic tests as needed. The goal is to both identify the cause of bleeding and rule out serious conditions like colorectal cancer.

It's important to provide your doctor with detailed information about your symptoms, as this helps guide the diagnostic process. Be prepared to discuss when you first noticed the bleeding, how often it occurs, the amount of blood, the color and consistency of blood, associated symptoms, your bowel habits, medications you take, your diet and lifestyle, family history of GI conditions, and any relevant medical history.

Physical Examination

The physical examination for rectal bleeding typically includes assessment of your vital signs, abdominal examination to check for tenderness, masses, or organ enlargement, and a digital rectal examination (DRE). During the DRE, the doctor inserts a gloved, lubricated finger into the rectum to feel for abnormalities such as hemorrhoids, masses, or tenderness, and to check for blood.

While the rectal examination may feel awkward, it provides important information and is typically brief. If you feel anxious, tell your doctor - they can explain what they're doing and help you feel more comfortable.

Endoscopic Procedures

Endoscopy involves using a flexible tube with a camera and light source to directly visualize the inside of the digestive tract. Different types of endoscopy examine different portions of the GI tract:

Colonoscopy is considered the gold standard for evaluating rectal bleeding, particularly in individuals over 45 or those with risk factors for colorectal cancer. During colonoscopy, the doctor can not only see abnormalities but also take tissue samples (biopsies) and remove polyps if found.

Blood Tests

Blood tests commonly ordered for patients with rectal bleeding include complete blood count (CBC) to check for anemia from blood loss, comprehensive metabolic panel to assess overall health and organ function, coagulation studies (PT/INR, PTT) to evaluate blood clotting, and iron studies if iron deficiency anemia is suspected.

Stool Tests

Stool tests can provide valuable diagnostic information. The fecal immunochemical test (FIT) detects hidden (occult) blood in stool that isn't visible to the naked eye. Stool cultures can identify infectious causes of bloody diarrhea. Stool DNA tests can detect genetic markers associated with colorectal cancer and advanced polyps.

Imaging Studies

In some cases, imaging studies may be needed. CT colonography (virtual colonoscopy) uses CT scanning to create detailed images of the colon - it's less invasive than traditional colonoscopy but cannot remove polyps or take biopsies. CT scan of the abdomen and pelvis may be used in emergency situations or when colonoscopy isn't possible. Capsule endoscopy involves swallowing a pill-sized camera to examine the small intestine, which is difficult to reach with traditional endoscopy.

How Is Blood in Stool Treated?

Treatment depends on the underlying cause. Hemorrhoids are treated with dietary changes, topical medications, and sometimes procedures like rubber band ligation. Anal fissures often heal with conservative measures. Inflammatory bowel disease requires ongoing medication management. Polyps are removed during colonoscopy. Colorectal cancer treatment may include surgery, chemotherapy, and radiation. Emergency treatment focuses on stabilization and stopping active bleeding.

The treatment approach for blood in stool depends entirely on identifying and addressing the underlying cause. There is no single treatment for rectal bleeding itself - rather, treatment is directed at the specific condition causing the bleeding. This is why proper diagnosis is so important before beginning treatment.

Treatment for Hemorrhoids

Hemorrhoid treatment typically begins with conservative measures. Dietary modifications including increased fiber intake (25-30 grams daily) and adequate fluid consumption help soften stools and reduce straining. Over-the-counter treatments include topical creams, ointments, suppositories, and medicated wipes containing ingredients like hydrocortisone, witch hazel, or lidocaine. Warm sitz baths (sitting in a few inches of warm water for 15-20 minutes) can provide relief. Lifestyle changes such as avoiding prolonged sitting, not straining during bowel movements, and regular exercise are also beneficial.

For hemorrhoids that don't respond to conservative treatment, office-based procedures may be recommended. Rubber band ligation is the most common procedure, where small rubber bands are placed around internal hemorrhoids to cut off their blood supply. Other options include sclerotherapy (injection of a solution to shrink hemorrhoids), infrared coagulation, and in severe cases, surgical hemorrhoidectomy.

Treatment for Anal Fissures

Most anal fissures heal within 4-6 weeks with conservative measures similar to those used for hemorrhoids. These include increased fiber and fluids, stool softeners, sitz baths, and avoiding straining. Topical treatments such as nitroglycerin ointment or calcium channel blockers (like diltiazem gel) can help relax the anal sphincter and improve blood flow to promote healing.

Chronic fissures that don't heal with conservative treatment may require botulinum toxin injection into the anal sphincter or surgical intervention (lateral internal sphincterotomy).

Treatment for Inflammatory Bowel Disease

IBD requires ongoing medical management, typically under the care of a gastroenterologist. Treatment goals include inducing and maintaining remission, preventing complications, and improving quality of life. Medications used include aminosalicylates (5-ASA drugs like mesalamine), corticosteroids for acute flares, immunomodulators (azathioprine, 6-mercaptopurine), and biologic therapies (anti-TNF agents, integrin inhibitors, IL-12/23 inhibitors).

Surgery may be needed for patients who don't respond to medical therapy or develop complications. In ulcerative colitis, removal of the colon (colectomy) can be curative. Crohn's disease surgery is typically used to treat complications rather than cure the disease.

Treatment for Polyps and Colorectal Cancer

Colon polyps are typically removed during colonoscopy (polypectomy). This is both diagnostic (allowing examination of the polyp tissue under a microscope) and therapeutic (removing potentially precancerous growths). Follow-up colonoscopy intervals depend on the number, size, and type of polyps found.

Colorectal cancer treatment depends on the stage of cancer and may include surgery to remove the cancer and nearby lymph nodes, chemotherapy, radiation therapy, and targeted therapies or immunotherapy for advanced disease. Treatment is typically coordinated by a team including surgeons, oncologists, and other specialists.

Emergency Treatment for Severe Bleeding

Patients with severe gastrointestinal bleeding may require hospitalization for stabilization, which may include intravenous fluids and blood transfusions, monitoring of vital signs and blood counts, identification and treatment of the bleeding source, and medications to reduce stomach acid or help blood clot. Endoscopic treatment can often stop active bleeding using techniques like cauterization, injection of medications, or placement of clips. Surgery may be needed for bleeding that can't be controlled by other means.

How Can You Prevent Blood in Stool?

Prevention strategies focus on maintaining digestive health and reducing risk factors. Key measures include eating a high-fiber diet, staying well hydrated, exercising regularly, maintaining a healthy weight, avoiding prolonged sitting and straining, limiting alcohol, not smoking, using medications cautiously, and getting recommended colorectal cancer screening starting at age 45.

While not all causes of rectal bleeding can be prevented, there are many steps you can take to reduce your risk of developing conditions that cause blood in stool and to maintain overall digestive health. These preventive measures can help you avoid hemorrhoids, anal fissures, and other common causes of bleeding, and may also reduce your risk of colorectal cancer.

Dietary Measures

A high-fiber diet is one of the most important factors in preventing constipation and conditions like hemorrhoids and anal fissures. Adults should aim for 25-30 grams of fiber daily from sources such as fruits and vegetables, whole grains, legumes, nuts, and seeds. Increase fiber gradually to avoid bloating and gas, and be sure to drink plenty of water as you increase fiber intake.

Adequate hydration helps keep stools soft and easy to pass. Aim for 8 or more glasses of water daily. Limit foods and beverages that can contribute to constipation or irritate the digestive tract, including processed foods, excessive caffeine, and alcohol.

Lifestyle Modifications

Regular physical activity promotes healthy bowel function and reduces the risk of colorectal cancer. Aim for at least 150 minutes of moderate-intensity exercise per week. Maintaining a healthy weight also reduces pressure on rectal veins and decreases colorectal cancer risk.

Avoid behaviors that increase rectal pressure. Don't strain during bowel movements - if you need to strain, your stool is probably too hard. Don't sit on the toilet for extended periods (put down the phone!). Go to the bathroom when you feel the urge rather than waiting.

Medication Awareness

Use NSAIDs (ibuprofen, aspirin, naproxen) cautiously and at the lowest effective dose for the shortest necessary duration. Take them with food when possible. If you need long-term pain management, discuss alternatives with your doctor. If you take blood thinners or have bleeding risk factors, discuss the appropriate monitoring and precautions with your healthcare provider.

Colorectal Cancer Screening

Regular screening is crucial for preventing colorectal cancer or detecting it at an early, treatable stage. Current guidelines recommend that average-risk adults begin screening at age 45 and continue until at least age 75. People with increased risk factors (family history, personal history of polyps, inflammatory bowel disease) may need to start screening earlier.

Screening options include colonoscopy (usually every 10 years if normal), fecal immunochemical test or FIT (annually), stool DNA test (every 1-3 years), and flexible sigmoidoscopy (every 5-10 years). Talk to your doctor about which option is best for you.