What Does Blood in Your Stool Mean?

Blood in your stool is often caused by a common, treatable problem such as hemorrhoids or a small tear in the anus, but it can also come from the colon, stomach or small intestine, and it should not be ignored. Black, tarry stool, heavy bleeding, or bleeding with dizziness needs emergency care. This article explains what the color and amount may suggest, common causes, how clinicians investigate, and when to get seen.

What blood in your stool can mean

Blood in the stool is a sign that bleeding is happening somewhere along the digestive tract, which runs from the mouth to the anus. According to MedlinePlus on gastrointestinal bleeding, the blood may be bright red, dark red, or black, and sometimes it is too small an amount to see at all.

The symptom is common, and in many cases the cause is minor. Still, several different conditions can cause it, and one look at the toilet bowl cannot tell you which one you have. The sections below help you sort out what is more likely and how urgent it may be.

What the color and pattern may suggest

Where the blood comes from often affects how it looks. The blood changes as it travels through the digestive tract and meets digestive juices. These patterns are clues, not a diagnosis.

Not everything red or black is blood. Beets, red gelatin and some food dyes can color stool red. Iron supplements and bismuth subsalicylate products such as Pepto-Bismol can turn stool dark or black. Stool from these causes is usually not tarry and sticky, but it can be hard to judge at home. If you are unsure, seek care, and a clinician can test the stool for blood.

Common causes near the anus and rectum

The most frequent source of bright red blood is the anal area. MedlinePlus describes hemorrhoids as swollen veins in the anus and lower rectum that can bleed, itch or hurt, especially with straining. Our related article on hemorrhoids covers home care in more detail.

An anal fissure is a small tear in the lining of the anus. It often causes sharp pain during or after a bowel movement along with a streak of bright red blood. Hard stools and straining can contribute. MedlinePlus lists anal disorders such as fissures, fistulas and abscesses together, and several of them can cause bleeding.

Other conditions in the rectum can also cause bleeding. MedlinePlus rectal disorders include inflammation of the rectal lining (proctitis), which has several possible causes, including inflammatory bowel disease, infections and some medical treatments. Because these look similar from the outside, a clinician usually needs to examine you before treatment is chosen.

Causes in the colon and higher up

When blood is mixed into the stool, or when it is darker, the source may be further along the tract. Several conditions are possible.

• Diverticular disease. Small pouches can form in the wall of the colon. Sometimes one bleeds, often without pain. The bleeding can be heavy and sudden.
• Inflammatory bowel disease. Ulcerative colitis causes sores in the lining of the colon and rectum and is often associated with bloody diarrhea. Crohn's disease can affect any part of the digestive tract and can also cause bloody stool, often with abdominal pain and weight loss.
• Infections. Some bowel infections cause bloody diarrhea with cramps and sometimes fever. MedlinePlus on diarrhea notes that some infections need treatment and that dehydration is a concern when diarrhea is severe or lasts. If loose stools have gone on for weeks, our article on diarrhea lasting more than two weeks may help.
• Polyps. Colonic polyps are growths on the lining of the colon or rectum. Many cause no symptoms, some bleed, and some types can change over time into cancer, which is why clinicians often remove them.
• Ulcers and irritation of the stomach or upper intestine. Bleeding from these areas can produce black stool. Regular use of nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen, may contribute in some people.
• Reduced blood flow to the bowel. Less commonly, the intestine can be injured when its blood supply is reduced. This usually comes with significant abdominal pain.

Cancer of the colon or rectum can also cause blood in the stool. It is much less common than the everyday causes above, and blood alone does not establish it. It is one reason clinicians take persistent or unexplained bleeding seriously, especially with a change in bowel habits, unintended weight loss, iron deficiency or a family history of colorectal cancer or polyps. Many cases of blood in the stool turn out to have a benign explanation, but finding that out requires evaluation rather than guessing.

Why heavy bleeding and black stool are different

A small streak of blood and a large loss of blood are different problems. When a lot of blood is lost, the body cannot circulate enough to supply the brain and heart. Signs include lightheadedness, fainting, a fast or pounding heartbeat, cold or clammy skin, shortness of breath, chest pain, and confusion. These signs can progress quickly. If you notice them, treat the situation as an emergency and call 911.

Black, tarry stool deserves special attention because it may suggest bleeding higher in the digestive tract, where bleeding can be significant. It needs emergency evaluation even if you otherwise feel fine. Vomiting blood, or vomit that looks like coffee grounds, is a related warning sign and also calls for emergency care, particularly with weakness, dizziness or abdominal pain.

Severe abdominal pain with a hard, rigid belly, high fever or inability to keep fluids down alongside bloody stool can point to a serious complication such as a perforation or severe infection. These also call for emergency care. Our article on causes of abdominal pain explains how different belly pain patterns are sorted out.

Medicines that can raise the chance of bleeding

Some medicines can make the digestive tract bleed more easily. Prescription blood thinners (anticoagulants) and antiplatelet drugs such as aspirin affect clotting. NSAIDs can irritate the lining of the stomach and intestine, and their labels carry a warning about stomach and intestinal bleeding, with a higher concern in older adults and in people who take them for long periods or alongside blood thinners.

If you see blood in your stool and take any of these, call your prescriber or clinician the same day so they can decide what to do. Go to the emergency room if there is more than a streak of blood, the stool is black or tarry, or you feel lightheaded. Do not stop or change a prescribed blood thinner, aspirin or heart medicine on your own, because stopping can carry its own serious risks, for example after a stent or with an irregular heart rhythm. Until you have been evaluated, it is reasonable to avoid over-the-counter NSAIDs and aspirin that were not prescribed for you; ask your pharmacist or clinician about options that fit your health history. Bleeding while on a blood thinner is a reason to be assessed, even if the amount seems small.

How clinicians find the cause

There is no single test for blood in the stool. Clinicians combine your history, an examination and testing, and the choice depends on your age, symptoms and risk factors. Expect questions about the color and amount of blood, pain, changes in bowel habits, weight loss, medicines, travel, family history and recent illness.

• Physical examination. This may include a gentle look at the anus and a digital rectal exam to check for hemorrhoids, fissures or masses.
• Blood tests. A complete blood count can show anemia, and iron studies may show whether blood has been lost over time.
• Stool tests. These can look for hidden blood or for infectious causes of diarrhea.
• Endoscopy. Sigmoidoscopy or colonoscopy uses a thin, flexible camera to view the lining of the rectum and colon. Polyps can often be removed during colonoscopy. An upper endoscopy looks at the esophagus, stomach and upper small intestine when an upper source is suspected.
• Imaging. A CT scan or other imaging may be used when bleeding is heavy or the cause is unclear.

Tell your clinician about the specific things you noticed, even if they feel embarrassing. A description like "bright red blood on the paper after straining" versus "dark blood mixed through loose stool for three weeks" can steer the evaluation. Ask them which tests suit you and how colorectal cancer screening fits your age and family history.

What treatment can look like

Treatment depends on the cause, so it makes sense to know the source before deciding on a remedy. For hemorrhoids and small fissures, clinicians often discuss eating more fiber, drinking enough fluids, avoiding long stretches on the toilet and straining, and options sold at the pharmacy. Ask your clinician or pharmacist which products are suitable for you.

Inflammatory bowel disease is managed over the long term, often with a gastroenterologist, and outcomes vary. Polyps are commonly removed during colonoscopy. Bowel infections may need fluids, and sometimes specific treatment. Bleeding ulcers can be treated through an endoscope and with medicines, and the cause of the ulcer is addressed as well. Heavy bleeding is treated in a hospital, where fluids, blood products and procedures to stop the bleeding may be used.

Blood in a child's or infant's stool

Blood in a baby's or child's stool has its own set of causes, and some are specific to age. Seek emergency care right away for an infant or child with bloody stool who is limp, very sleepy, pale, has a swollen, tender or hard belly, is vomiting green fluid or blood, or has bouts of severe crying or belly pain that come in waves, sometimes with the legs drawn up. These signs can point to a blockage or bowel injury that needs urgent treatment. For an otherwise well-appearing child with a small amount of blood, call their pediatrician the same day. Do not give your child medicines to stop diarrhea or treat pain unless their clinician says so, and follow the product label and your pediatrician or pharmacist for any medicine.

What to do while you arrange care

If you do not have emergency signs, a few steps can help the visit go better.

• Note when the bleeding started, how often it happens, the color, and whether it is on the paper, in the bowl or mixed in the stool.
• List all your medicines and supplements, including aspirin, NSAIDs, iron and blood thinners.
• Write down any pain, weight change, fever, fatigue or change in bowel habits.
• If you can do so comfortably, take a photo of the toilet bowl. It can help your clinician judge the color.
• Drink fluids, and mention it to your clinician if you cannot keep them down.

Even when you suspect hemorrhoids, it is reasonable to have bleeding checked, particularly if it lasts, returns, or is new for you. Self-diagnosis can miss a second problem that looks the same from the outside.

When to Seek Medical Care