Finding blood in your stool is understandably alarming, but the right next step depends on what the blood looks like, how much there is, and what other symptoms you’re experiencing. Most cases trace back to something treatable like hemorrhoids or a small tear in the anal lining. Some cases, though, signal something more serious that needs prompt medical attention. Here’s how to assess what’s happening and what to do about it.
When to Call 911
Heavy rectal bleeding paired with signs of shock is a medical emergency. If you’re passing a large amount of blood and experiencing any of the following, call emergency services immediately:
- Rapid, shallow breathing
- Dizziness or lightheadedness when you stand up
- Fainting or confusion
- Blurred vision
- Cold, clammy, pale skin
- Very low urine output
These symptoms mean your body is losing blood faster than it can compensate. This is rare, but it requires emergency treatment, not a scheduled appointment.
What the Color of the Blood Tells You
The color and consistency of blood in your stool is a useful clue about where the bleeding is coming from.
Bright red blood on the toilet paper or in the bowl typically comes from the lower part of your digestive tract: the colon, rectum, or anus. This is the most common presentation and often points to hemorrhoids or a fissure. That said, very rapid bleeding from higher up in the digestive tract can also produce bright red blood, though this is less common and usually involves a large volume.
Dark red or maroon blood mixed into the stool suggests bleeding from somewhere in the colon or small intestine, where the blood has had some time to break down during transit.
Black, tarry stool (sometimes with a distinctly foul smell) points to bleeding in the stomach or upper small intestine. Digestive chemicals interact with the blood during its long journey through the gut, turning it dark and sticky. About 90% of significant GI bleeding episodes come from the upper digestive tract, and this dark appearance is the hallmark. A painless black stool can indicate a silent ulcer, a growth, or a ruptured blood vessel.
One important caveat: certain foods and supplements can mimic these colors. Iron supplements, bismuth (the active ingredient in some stomach medications), and foods like beets or black licorice can change stool color without any bleeding at all. If you’ve recently taken any of these, that may explain what you’re seeing.
The Most Common Causes
Hemorrhoids
Hemorrhoids are swollen blood vessels in or around the anus, and they’re the single most common reason for blood in the stool. You’ll typically notice bright red blood on the toilet paper or dripping into the bowl. Most hemorrhoids don’t cause pain, though external ones that develop a clot can be quite tender. Risk factors include straining during bowel movements, sitting for long periods, chronic constipation or diarrhea, pregnancy, obesity, and being over 50.
Anal Fissures
A fissure is a small tear in the lining of the anus, and it tends to hurt more than a hemorrhoid. You’ll feel a sharp or burning pain during and sometimes after a bowel movement, along with bright red blood. Fissures can develop from passing hard stools, chronic diarrhea, or inflammatory conditions like Crohn’s disease. Most heal on their own within a few weeks with proper care.
Stomach and Duodenal Ulcers
Ulcers in the stomach or upper small intestine can bleed slowly, producing black, tarry stool rather than visible red blood. You may also notice burning or gnawing abdominal pain, especially between meals. Long-term use of common pain relievers is a major risk factor here (more on that below), as is infection with a specific type of stomach bacteria.
Inflammatory Bowel Disease
Crohn’s disease and ulcerative colitis cause chronic inflammation in the digestive tract that can lead to bloody diarrhea. If your bleeding comes with ongoing abdominal cramps, unintentional weight loss, persistent fatigue, fever, or loss of appetite, inflammatory bowel disease is worth investigating. These conditions can also cause symptoms outside the gut, including joint pain, mouth ulcers, skin rashes, eye inflammation, and kidney stones.
Colorectal Polyps or Cancer
Polyps are small growths on the colon lining that can bleed intermittently. Most are harmless, but some can become cancerous over time. Colorectal cancer itself can cause blood in the stool, changes in bowel habits, unexplained weight loss, and persistent abdominal discomfort. This is one of the key reasons not to assume bleeding is “just hemorrhoids,” especially if you’re over 45 or have a family history.
Medications That Increase Bleeding Risk
If you regularly take over-the-counter pain relievers, they could be contributing to or directly causing the bleeding. Non-selective anti-inflammatory drugs significantly raise the risk of gastrointestinal bleeding. Ibuprofen roughly doubles the risk. Naproxen increases it more than fourfold. Diclofenac falls in between at about 3.4 times the baseline risk. Some prescription anti-inflammatories carry even higher risk.
Blood thinners, whether prescription anticoagulants or even daily aspirin, also increase the likelihood of GI bleeding and can make minor bleeds harder to stop. If you’re on any of these medications and notice blood in your stool, bring it up with your doctor promptly. Don’t stop a prescribed blood thinner on your own, but do make the call.
What to Do Right Now
If the bleeding is small, you’re not in pain, and you feel fine otherwise, you don’t need to rush to the emergency room. But you should still make a doctor’s appointment, especially if this is the first time it’s happened or if it persists beyond a couple of days. In the meantime, there are practical steps to take.
Increase your fiber intake. The federal dietary guidelines recommend about 28 grams of fiber per day for a standard 2,000-calorie diet, and most people fall well short. Fiber softens stool and reduces the straining that causes hemorrhoids and fissures. Good sources include beans, lentils, whole grains, fruits, and vegetables. Increase gradually to avoid bloating. Drink plenty of water alongside the fiber to help it work properly.
Avoid prolonged sitting on the toilet. Scrolling on your phone for 20 minutes creates sustained pressure on the veins around the anus. Get in, get out. If you’re prone to hemorrhoids, a warm sitz bath (sitting in a few inches of warm water for 10 to 15 minutes) can reduce swelling and discomfort.
Note the details. Before your appointment, pay attention to the blood’s color, whether it’s on the surface of the stool or mixed in, how often it happens, and any accompanying symptoms like pain, changes in bowel habits, or weight loss. This information helps your doctor narrow down the cause quickly.
What Happens at the Doctor
Your doctor will likely start with a physical exam and questions about your symptoms, diet, medications, and family history. Depending on what they suspect, the next step could be a stool test or a visual exam of the colon.
A fecal immunochemical test (FIT) is a simple at-home stool sample that detects hidden blood. It’s convenient and highly specific, correctly ruling out serious problems about 95% of the time. However, its sensitivity for catching advanced growths is only around 16%, which means it can miss things. That’s why it’s designed to be repeated yearly as a screening tool, not used as a one-time definitive test.
A colonoscopy is the gold standard. It detects advanced growths with about 98.5% sensitivity and allows the doctor to remove polyps or take tissue samples during the same procedure. The U.S. Preventive Services Task Force recommends routine colorectal screening starting at age 45, with colonoscopy every 10 years or annual FIT testing as the main options. If you’re experiencing symptoms like blood in the stool, your doctor may recommend a colonoscopy regardless of your age or screening history.
The prep (clearing your bowels the day before) is the most unpleasant part. The procedure itself is done under sedation, and most people don’t remember it. You’ll typically get results within a week or two, and the vast majority of colonoscopies come back either normal or show easily treatable findings like small polyps.
Signs That Need Prompt Attention
Not every instance of blood in the stool requires an urgent visit, but certain patterns shouldn’t wait for a routine appointment weeks away. Push for a sooner evaluation if you notice blood in your stool on multiple occasions over days or weeks, if the bleeding is getting heavier, if you’re losing weight without trying, if your bowel habits have changed significantly, or if you’re passing black, tarry stool. A combination of bloody stool and persistent fatigue can indicate chronic blood loss leading to anemia, even when each individual episode seems minor.