Blood in your stool is usually caused by something minor and treatable, most often hemorrhoids or a small tear in the skin around your anus. That said, the color, amount, and accompanying symptoms all matter in figuring out what’s going on and whether you need medical attention soon.
What the Color of the Blood Tells You
The color is the single most useful clue to where the bleeding is coming from. Bright red or maroon blood typically means the source is lower in your digestive tract: your colon, rectum, or anus. This is the most common scenario and often points to hemorrhoids, a fissure, or inflammation in the large intestine.
Black, tarry stool is a different signal. It suggests bleeding higher up in your digestive system, such as your esophagus, stomach, or small intestine. Blood that travels a longer distance through your gut gets digested along the way, turning it dark. Black stool that looks like tar and has a strong odor warrants a prompt call to your doctor.
Before you worry, though, consider what you’ve eaten recently. Beets, tomatoes, and foods with red food coloring can make stool look reddish when there’s no blood at all. On the other end, blueberries, black licorice, iron supplements, Pepto-Bismol, and activated charcoal can all turn stool dark enough to mimic internal bleeding.
Hemorrhoids: The Most Common Cause
Hemorrhoids are swollen veins in the rectum or anus, and they’re the single most common reason people see blood in their stool. You’ll typically notice bright red blood on the toilet paper, on the surface of your stool, or dripping into the bowl. Internal hemorrhoids (inside the rectum) can bleed without any pain at all. External hemorrhoids often show up as small lumps around the anus and tend to cause an achy, itchy discomfort that comes and goes. Straining during bowel movements, sitting for long periods, pregnancy, and chronic constipation all increase the risk.
Anal Fissures: Small Tears, Sharp Pain
An anal fissure is a tiny tear in the lining of the anal canal, usually caused by passing a hard or large stool. The hallmark difference from hemorrhoids is pain: fissures cause a sharp, burning sensation that can last for hours after a bowel movement. Hemorrhoids rarely produce that level of pain. Fissures are usually invisible from the outside and don’t cause lumps or swelling. The bleeding is typically minor, showing up as a small streak of bright red on toilet paper or stool. Most fissures heal on their own within a few weeks once you soften your stool with more fiber and water.
Inflammatory Bowel Disease
If you’re seeing blood mixed into your stool along with persistent diarrhea, abdominal cramping, or fevers, inflammatory bowel disease (IBD) is a possibility worth investigating. IBD, which includes Crohn’s disease and ulcerative colitis, involves chronic inflammation of the digestive tract driven by an overactive immune system. That inflammation damages the intestinal lining, which is why bloody bowel movements are a primary symptom.
IBD is distinct from irritable bowel syndrome (IBS), even though the names sound similar. IBS can cause cramping, bloating, and changes in bowel habits, but it doesn’t cause visible inflammation or bleeding. If blood is present, it points toward IBD or another structural problem rather than IBS.
Other Possible Causes
Several other conditions can produce blood in your stool:
- Diverticulitis happens when small pouches in the colon wall become infected and inflamed. It can cause sudden, painless bleeding that’s sometimes heavy.
- Colon polyps are growths on the inner lining of the colon. Most are harmless, but some can bleed and, over time, develop into colorectal cancer.
- Gastroenteritis and infectious colitis (stomach bugs caused by bacteria or viruses) can irritate the intestinal lining enough to produce bloody diarrhea, usually alongside nausea and cramping.
- Peptic ulcers in the stomach or upper intestine can bleed slowly, producing black tarry stool rather than visible red blood.
- Certain medications, particularly blood thinners and anti-inflammatory drugs like ibuprofen, can increase the likelihood of bleeding anywhere in the digestive tract.
When It’s an Emergency
A small amount of bright red blood after straining is rarely an emergency. But heavy or continuous rectal bleeding, especially with severe abdominal pain or cramping, warrants an immediate trip to the emergency room.
Call 911 if you have significant bleeding along with any signs of shock: dizziness or lightheadedness when you stand up, rapid shallow breathing, blurred vision, fainting, confusion, nausea, cold and clammy skin, or very low urine output. These symptoms mean your body may be losing blood faster than it can compensate.
How Doctors Find the Source
If bleeding is recurrent, heavy, or accompanied by other symptoms, your doctor will want to identify the exact source. The process typically starts with a physical exam and a review of your symptoms, including the color and frequency of the bleeding. Depending on what they suspect, the next step may be a scope procedure: a flexible camera inserted into the rectum to visually inspect the lower colon, or a full colonoscopy to examine the entire large intestine. Stool tests can also check for hidden blood you can’t see with the naked eye.
The U.S. Preventive Services Task Force recommends that all adults begin routine colorectal cancer screening at age 45. If you’re at average risk, a colonoscopy every 10 years is one option. Less invasive alternatives include an annual stool test that checks for hidden blood, or a stool DNA test every one to three years. If you’re younger than 45 but noticing blood in your stool repeatedly, that’s reason enough to get evaluated rather than waiting for the standard screening age.
What to Pay Attention To
If you see blood once after a hard bowel movement and it doesn’t return, you’re most likely dealing with a fissure or a hemorrhoid that will resolve on its own. Increasing your fiber intake, drinking more water, and avoiding straining are the simplest steps to prevent it from happening again.
Track what you’re seeing. Note the color, how much blood there is, whether it’s on the surface of the stool or mixed in, and whether you have any pain, cramping, weight loss, or changes in bowel habits. That information helps a doctor narrow down the cause quickly if you do need to be evaluated. Recurrent bleeding, blood mixed into the stool rather than on its surface, unexplained weight loss, or a change in the shape or consistency of your stool are all reasons to get checked sooner rather than later.