Blood in Stool: Causes, Tests and When to Get Help

This article provides general health education, not a diagnosis or a personal treatment plan. Source-checking is editorial work and does not mean that a licensed clinician has reviewed this article. Use local emergency services and your own healthcare team’s advice when symptoms occur.

What does blood in stool mean?

Blood in stool is a symptom that needs an explanation. Bleeding can begin anywhere in the digestive tract, including the stomach, small intestine, colon or anus. It may appear suddenly, recur intermittently or remain too small to see. The first priority is deciding how urgently you need medical help. [1]

Red, maroon and black stools: what appearance can tell you

Common and important causes of blood in stool

Hemorrhoids

Hemorrhoids are a possible explanation for bright red bleeding after a bowel movement, especially blood on the paper, stool surface or in the bowl. Internal hemorrhoids often bleed without pain unless they protrude through the anus. External hemorrhoids more often cause itching, tenderness or a painful lump. Straining, prolonged toilet sitting, constipation, diarrhea and pregnancy can contribute. However, those symptoms overlap with other bowel conditions. Finding a familiar pattern does not establish that hemorrhoids caused this episode, and a past diagnosis does not settle every future episode. NIDDK recommends medical help for rectal bleeding. Describe any change from your usual symptoms, including how often bleeding occurs and whether it continues after the bowel movement. [4]

Anal fissures

A fissure is a small tear at the anus. A typical pattern is sharp pain while passing stool, followed by burning that can persist for hours, with bright red blood. Constipation is one possible trigger, but frequent diarrhea, childbirth and certain inflammatory or infectious conditions can also contribute. An examination helps distinguish a fissure from other causes of pain. Once a clinician has identified a fissure, keeping stools soft, avoiding delayed bowel movements and using a warm shallow bath may help. Persistent or worsening symptoms can require prescribed treatment to support healing or relax the anal muscles. Recurrent tears deserve reassessment rather than indefinite use of an assumed remedy. A fissure-like pain pattern is still not a diagnosis by itself. [5]

Diverticular bleeding

Diverticula are small pouches that push outward through weak places in the colon wall. Having these pouches is called diverticulosis; many people have no symptoms. A vessel in a pouch can rupture and cause diverticular bleeding, which can be severe. Diverticulitis means inflammation of the pouches and is a different complication. It commonly causes abdominal pain, often toward the lower left, sometimes with fever, chills, nausea or a change in bowel movements. These terms should not be used interchangeably when describing a previous diagnosis. Tell the clinician whether you were previously told about uncomplicated pouches, an inflammatory episode or an actual bleeding episode. Heavy bleeding needs emergency care regardless of whether diverticula were found on an earlier scan. [6]

Ulcerative colitis

Ulcerative colitis involves inflammation in the large intestine. Bleeding may occur with diarrhea, cramping, mucus or pus, an urgent need to use the toilet, or a continuing feeling that you need to pass stool even after the bowel is empty. That last symptom is called tenesmus. Illness severity varies, and more extensive disease can bring fatigue, fever, nausea or weight loss. Symptoms may disappear during remission and return during a relapse. Consequently, a period of normal bowel movements does not exclude an inflammatory condition. If you already have ulcerative colitis, explain how the current bleeding and bowel frequency compare with your usual baseline. The pattern and accompanying symptoms help your clinical team assess a possible flare and decide what evaluation is needed. [7]

Crohn’s disease

Crohn’s disease can cause diarrhea, abdominal cramps and weight loss, with symptoms depending on the location and severity of inflammation. Anemia, tiredness, reduced appetite and fever may accompany digestive symptoms. Some people also have painful joints, eye symptoms or skin changes. These wider symptoms can be relevant during assessment, so mention them rather than focusing only on the toilet appearance. Crohn’s disease involves an abnormal immune response and other interacting factors; researchers continue to study the roles of genes, the environment and the gut microbiome. A family history can be useful information, but it cannot confirm or exclude the disease. Blood tests, examination and other investigations are needed to interpret a symptom pattern; symptoms alone cannot distinguish Crohn’s disease from other bowel disorders. [8]

Infections and bloody diarrhea

Some intestinal infections cause bloody diarrhea. For example, certain E. coli infections produce severe cramps with watery or bloody stools, sometimes vomiting or fever. Bloody diarrhea needs medical advice rather than automatic treatment as an ordinary stomach upset. Do not start over-the-counter diarrhea-stopping medicine for bloody diarrhea or high fever without clinical advice. Some treatments that seem helpful can be harmful in Shiga toxin-producing E. coli infection, including certain antibiotic use. A clinician should decide whether testing and treatment are appropriate. One possible complication is hemolytic uremic syndrome, which can damage the kidneys. Little or no urination, unusual bruising, marked paleness, profound tiredness or reduced alertness after diarrheal illness needs emergency assessment. [9]

For broader background, see our guide to common causes of diarrhea and their warning signs. Bloody diarrhea still needs prompt medical assessment. [2]

Colon polyps

Polyps are growths on the lining of the colon or rectum. Most do not cause symptoms, so feeling well does not rule them out. When they do bleed, the result can be red streaks, darker stool, blood on toilet paper or iron deficiency and tiredness. Most polyps are not cancer, but some can develop into cancer over time. Finding and removing appropriate polyps helps prevent colorectal cancer. This is why an investigation may be recommended even when the bleeding seems minor. Age and family history influence the likelihood of polyps, but they are not a substitute for evaluating current symptoms. Tell the clinician about previous polyps and any available pathology or follow-up recommendations from an earlier colonoscopy. [10]

Colorectal cancer

Blood in stool can be a sign of colorectal cancer, although many other conditions cause the same symptom. Changes in bowel habits, a feeling of incomplete emptying, persistently different stool shape, unexplained weight loss, abdominal discomfort and fatigue may also prompt investigation. Blood may look bright red or dark. No single appearance confirms cancer or safely excludes it. A clinician considers the combination of symptoms, examination findings and personal and family history. Mention a parent, sibling or child with colorectal cancer, previous high-risk polyps and a history of inflammatory bowel disease. Risk increases with age, but people without an obvious risk factor can still develop cancer. The useful response to persistent symptoms is timely evaluation, rather than trying to estimate a diagnosis from color alone. [11]

Peptic ulcers

An ulcer in the stomach or duodenum can bleed and produce black, tarry stool or red-to-maroon blood mixed with stool. Ulcers may cause burning or dull upper abdominal pain, nausea, bloating or early fullness, but some produce no warning symptoms before a complication. Common causes include Helicobacter pylori infection and nonsteroidal anti-inflammatory medicines such as ibuprofen, naproxen and aspirin. Risk can rise with higher doses, prolonged use or combinations of these medicines. Report both prescription and nonprescription products when discussing bleeding. Sudden severe abdominal pain that persists, faintness, a rapid pulse or vomiting blood requires immediate care. Having little pain does not make an ulcer-related bleed safe to watch at home. [12]

Gastritis and injury to the stomach lining

Inflammation or damage to the stomach lining can also lead to bleeding if erosions or ulcers develop. Gastritis and gastropathy may cause upper abdominal discomfort, nausea, reduced appetite or a sense of fullness, but many people have no symptoms. Causes differ and can include H. pylori, long-term contact with irritating medicines, alcohol, bile reflux or an autoimmune process. Mild bleeding can be hidden rather than visibly changing each bowel movement. More obvious bleeding may produce tarry stool, vomiting blood, lightheadedness or breathlessness. Tell the clinician about any stomach surgery, regular pain medicines and prior testing for H. pylori. The goal is to identify the cause and its severity; the everyday description “indigestion” does not explain visible bleeding. [13]

Proctitis

Proctitis affects the rectal lining and can cause blood, mucus or pus, rectal pain, urgency and tenesmus. Possible causes include inflammatory bowel disease, infections, previous radiation treatment to the pelvis and changes after certain bowel operations. Some infections are sexually transmitted; others arise from organisms associated with foodborne illness. A private, factual account of symptoms, sexual exposure, recent antibiotics, radiotherapy and surgery can help the clinician select appropriate tests. These questions are relevant to choosing treatment, not a judgment about the patient. Similar symptoms can have different causes and therefore different treatments. Seek prompt medical attention for blood, mucus or pus from the rectum, especially with significant abdominal pain, rather than treating every episode as hemorrhoids. [14]

Fragile blood vessels: angiodysplasia

Angiodysplasia describes enlarged, fragile blood vessels in the bowel. It is more common in older adults and can occur in the colon or small intestine. Bleeding may be intermittent and painless, with visible red or dark blood, or so subtle that iron deficiency anemia is the main clue. Weakness, tiredness and breathlessness may therefore matter even without dramatic bleeding in the toilet. The condition is different from diverticular disease and is not itself cancer. Investigations can include colonoscopy and, when appropriate, imaging of blood vessels. Treatment depends on the amount and persistence of bleeding; options may include treating the vessel through an endoscope or angiography. The absence of pain does not tell you whether blood loss is important. [15]

Reduced blood flow to the intestine

An interruption in the intestine’s blood supply can injure bowel tissue and cause blood in stool. In small-intestinal ischemia, severe abdominal pain is a central warning sign and may occur with vomiting, diarrhea or fever. Causes can include a blocked vessel, very low blood pressure, or bowel trapped by a hernia or scar tissue. Some people have risk factors such as an irregular heart rhythm or vascular disease, but a reader should not try to diagnose this from a checklist. Severe or rapidly worsening abdominal pain needs immediate assessment. Prompt treatment matters because tissue can be permanently damaged when its blood supply is inadequate. Imaging and sometimes surgery are needed to establish what is happening. [16]

Bleeding related to liver disease

Advanced liver disease can lead to enlarged veins called varices in the esophagus or stomach. These veins may rupture and bleed heavily. A person can have varices without symptoms before bleeding begins. Warning signs include vomiting blood, black tarry stool, blood in stool, lightheadedness or paleness. Suspected bleeding in someone with known liver disease needs immediate medical attention. Hospital treatment focuses on stopping the bleeding quickly and preventing shock. Endoscopy may allow the team to place bands around bleeding veins, with other medicines or procedures used when needed. Because bleeding can recur, follow-up treatment for the varices and underlying liver condition remains important after the immediate episode has been controlled. [17]

Medicines: what your clinician needs to know

Anticoagulants reduce the blood’s ability to form clots and can increase bleeding. Examples include warfarin and newer direct oral anticoagulants. Antiplatelet medicines, including low-dose aspirin, work differently but are also relevant to the medication history. Blood in stool or black stool while taking an anticoagulant needs prompt medical advice; severe or recurrent bleeding needs immediate attention. Ask the treating clinician what to do about your next dose rather than independently stopping, skipping or changing treatment. The reason you take the medicine also matters, because it protects against potentially dangerous clots. Tell the team about new medicines, nonprescription products and planned procedures. If you take warfarin, provide recent monitoring information if available, without delaying urgent care to look for it. [18]

Read the active ingredients on products used for heartburn, headache, colds or other everyday symptoms. Some antacid combinations contain aspirin, so a medicine bought for an upset stomach can itself contribute to stomach or intestinal bleeding. FDA identifies increased risk with factors such as older age, previous ulcers, anticoagulant use, steroid use, additional NSAIDs or substantial alcohol intake. A pharmacist can help identify overlapping ingredients when brand names are confusing. Bring the packages or a complete list to the assessment. This warning is not a general instruction to stop prescribed aspirin: its benefits and risks depend on why it was prescribed. Discuss the actual product and situation with a clinician, particularly when bleeding has already occurred. [19]

Children and pregnancy need their own assessment

Blood in a child’s stool

Constipation can be part of a child’s history, especially with hard, painful stools and attempts to delay going to the toilet. A child may withhold because passing stool hurts, because public toilets feel uncomfortable, or because they do not want to interrupt play. Stool held in the colon can become drier and harder. Sometimes leakage around retained stool looks like diarrhea, so parents should describe the whole pattern. Blood should still be reported rather than assumed to be ordinary constipation. NIDDK advises seeing a doctor right away when constipation occurs with rectal bleeding, blood in stool, vomiting, persistent abdominal pain, bloating or weight loss. Adult laxative doses and adult diagnostic assumptions are not an appropriate substitute for pediatric advice. [22]

In a baby or young child, episodes of severe abdominal pain with paleness, unusual tiredness or floppiness can signal an emergency. One possible cause is intussusception, in which one segment of bowel slides into another and creates a blockage. Vomiting, a swollen abdomen and blood or mucus in stool may follow, but caregivers should not wait for every feature to appear. The condition can impair blood flow and become serious quickly. Seek emergency assessment for this combination of symptoms. Ultrasound is commonly used to confirm the diagnosis, and hospital treatment may involve an air enema or an operation. This is a reason for urgent evaluation, not a condition to test for or treat at home. [21]

Bleeding during pregnancy

Hemorrhoids can occur during pregnancy and may cause bright red bleeding after passing stool, itching, soreness or swelling around the anus. If constipation contributes, the maternity team may recommend suitable changes to food, fluids and activity to keep stools easier to pass. Avoid straining, and clean gently rather than repeatedly rubbing a sore area. A cool damp cloth can ease local discomfort. Ask your midwife, doctor or pharmacist before using hemorrhoid creams or medicines during pregnancy, because a product’s suitability depends on the person and the product. These measures address symptoms associated with piles; they do not establish that piles explain new bleeding. Tell your maternity team exactly what you have noticed and ask for advice appropriate to your pregnancy. [20]

If you are pregnant and unsure whether blood comes from the rectum or vagina, contact your maternity service urgently rather than assuming it is hemorrhoids. Vaginal spotting also deserves advice. Heavy vaginal bleeding, severe abdominal or shoulder pain, faintness or loss of consciousness requires emergency help. Tell the service how many weeks pregnant you are and what symptoms accompany the bleeding. [35]

What happens at a medical assessment?

Expect questions about symptoms, medicines, past bleeding and relevant family history. The clinician may check blood pressure, pulse and temperature and examine the abdomen. Tests are selected to assess the severity of bleeding and find its location and cause; they are not identical for every patient. [1]

A rectal examination may be part of the visit. The clinician checks the outside of the anus and gently uses a lubricated, gloved finger to examine the lower rectum for findings such as lumps or swelling. The examination usually takes only a few minutes. It may be uncomfortable, so tell the clinician about pain or anxiety before it begins. You can ask whether a clinician of your preferred gender is available and request a chaperone or another support person. Afterward, ask what the examination showed and whether further tests are needed. An office examination is one part of assessment; the clinician may still recommend another investigation to explain symptoms that it cannot fully evaluate. [32]

Blood and stool tests answer different questions

Colonoscopy

Colonoscopy allows a doctor to inspect the rectum and colon with a flexible camera. It can identify inflamed tissue, ulcers, polyps and other abnormalities, and tissue samples or polyps may be removed for laboratory examination. Preparation normally includes prescribed bowel-cleansing instructions and a temporary dietary plan. Follow the team’s directions rather than a generic internet schedule, and discuss all medicines and supplements beforehand. Arrange transport if sedation is used. Ask when biopsy results will arrive and how you will receive them. Afterward, seek care for severe abdominal pain, fever, persistent or worsening bloody bowel movements, bleeding that will not stop, dizziness or weakness. Delayed bleeding can occur after a procedure, so new symptoms should be reported even after returning home. [24]

Upper endoscopy

If the suspected source is higher in the digestive tract, an upper endoscopy may be more useful than starting with a colon examination. A flexible camera passes through the mouth to inspect the esophagus, stomach and duodenum. Clinicians can use it to investigate symptoms, take samples or treat some bleeding lesions. Tell the team about allergies, medical conditions and all medicines, including aspirin, blood thinners, diabetes treatments and iron. Preparation includes individualized instructions about eating, drinking and medicines. Do not decide on dose changes yourself. Sedation or throat-numbing medicine may be offered, and you may need someone to take you home. Ask what the examination can answer and whether another test will be needed afterward. [25]

Flexible sigmoidoscopy

Flexible sigmoidoscopy examines the rectum and lower part of the colon. It can help investigate bleeding, bowel changes, abdominal pain or unexplained weight loss and may reveal inflammation, ulcers or polyps. It usually covers less bowel than a colonoscopy, which is an important limitation to understand. It may take less time, and sedation is not always needed. If abnormal tissue or polyps are found, a colonoscopy may be recommended to inspect the rest of the colon. Ask which part of the bowel will be examined, why this test fits your symptoms and what would trigger additional investigation. The name of the procedure matters when reporting past tests: a lower-bowel examination is not automatically an examination of the whole colon. [26]

Capsule endoscopy

Sometimes a small-bowel capsule examination is considered after other camera tests, particularly when bleeding or anemia remains unexplained. You swallow a small camera that sends images to recording equipment as it moves through the digestive tract. Preparation and eating instructions come from the endoscopy service. Tell the team about swallowing problems, earlier abdominal surgery, a history of bowel blockage and implanted medical devices before the appointment. A capsule can occasionally become stuck, particularly where the bowel is narrowed. The team may use a dissolvable patency capsule first when it needs to check that passage is safe. Follow the service’s instructions for returning the recorder and confirming capsule passage; do not assume that every capsule test has the same preparation or risks. [31]

Collecting a stool sample

If a stool sample is requested, use the supplied container and follow the local collection instructions. Keep urine and toilet water out of the sample: a clean disposable container or suitable collection material can catch stool before it touches the water. The service may want a portion containing blood or mucus, so read the directions rather than avoiding those areas. Seal and label the container as instructed, dispose of used collection materials safely and wash your hands thoroughly. Return the sample promptly using the specified route. If you cannot return it within the advised time, ask the service what to do about storage or recollection. Use the collection kit and instructions supplied for the test your clinician actually requested. [33]

Care while arranging assessment and follow-up

Diarrhea or vomiting can cause dehydration alongside the problem producing bleeding. Watch for reduced urination, dark urine, dry mouth, persistent dizziness or unusual drowsiness; babies may have fewer wet diapers or few tears. If you can drink and have no contrary medical instructions, small frequent sips may be easier than large drinks when nauseated. A pharmacist or clinician can recommend an appropriate oral rehydration solution. Serious dehydration needs urgent treatment, while confusion, difficulty waking, cold skin or breathing difficulty requires emergency help. For infants, continue usual breast or formula feeds as advised and do not dilute formula. Rehydration supports fluid replacement; it does not identify or treat the cause of blood in stool. [23]

Treatment depends on the source and severity. Clinicians may control bleeding during endoscopy, use medicines or blood-vessel procedures, or recommend surgery when necessary. Follow-up also addresses the underlying condition and medicine-related risks so that stopping one episode is not the end of care. [1]

Screening and symptom investigation are different

Colorectal screening is intended to find disease before symptoms develop. In the United States, average-risk screening generally begins at age forty-five, while some people with family history, inherited conditions or inflammatory bowel disease need an earlier or different plan. Local screening programs vary. Current bleeding is a symptom to discuss now, rather than a reason to wait until a routine screening invitation arrives. If a screening test is abnormal, complete the recommended follow-up; the screening result alone is not a final diagnosis. If you have already been screened, tell the clinician which test you had, when it was done and what follow-up was recommended. That history helps frame current assessment, but it should not be used to dismiss new or changing symptoms. [34]

The original video below is retained for continuity. Its age, medical accuracy and recommendations have not been independently reviewed for this update. Use the current written guidance and advice from qualified healthcare professionals for decisions about symptoms, medicines and care.