Rectal bleeding is extremely common, affecting roughly 1 in 7 adults at some point, and the most likely cause is hemorrhoids or a small tear in the skin around the anus. That said, blood from your bottom can signal a range of conditions from mild to serious, so the color of the blood, how much there is, and what other symptoms you’re experiencing all matter when figuring out what’s going on.
Hemorrhoids: The Most Common Cause
Internal hemorrhoids are swollen blood vessels inside the rectum, and they’re the single most frequent reason people notice blood after a bowel movement. The bleeding is typically bright red, appearing as streaks on toilet paper, on the surface of your stool, or dripping into the bowl. Internal hemorrhoids usually don’t hurt because the tissue inside the rectum has very few pain-sensing nerves. You might not even know they’re there until you see blood.
External hemorrhoids sit just outside the anus and are more likely to cause a noticeable lump, itching, or discomfort. When a blood clot forms inside one (a thrombosed hemorrhoid), it can be quite painful and may bleed if the skin over it breaks open. Most hemorrhoids develop from straining during bowel movements, sitting on the toilet for long periods, chronic constipation or diarrhea, pregnancy, or a low-fiber diet.
Anal Fissures: Small Tears, Sharp Pain
An anal fissure is a tear in the delicate lining of the anus. These tears typically cause a sharp, stinging pain during a bowel movement, sometimes followed by a throbbing ache that lasts hours afterward. You’ll often see bright red blood on toilet paper or on the surface of the stool. Fissures are common after passing a hard or unusually large stool, but they can also develop from chronic diarrhea or inflammation.
The key difference between a fissure and hemorrhoids is pain. Internal hemorrhoids rarely hurt, while fissures almost always do, especially during and immediately after going to the bathroom. Most fissures heal on their own within a few weeks once the stool is kept soft.
What Blood Color Tells You
The color and appearance of the blood offers a rough map of where the bleeding is coming from. Bright red blood on the tissue or in the bowl almost always originates near the anus or lower colon. This is the type you’d expect from hemorrhoids, fissures, or polyps in the lower part of the digestive tract.
Dark maroon blood mixed into the stool points to bleeding somewhere higher up in the colon. Black, tarry, sticky stools (with a distinctly foul smell) typically mean the bleeding source is in the stomach or upper small intestine. Blood that travels a long distance through the digestive tract gets chemically altered, which turns it black. If you’re seeing black tarry stools, that’s a more urgent situation than bright red spotting on your toilet paper.
Food Poisoning and Infections
Certain bacterial infections can cause bloody diarrhea by invading and ulcerating the lining of the intestines. The most common culprits include Salmonella, Campylobacter, Shigella, and certain strains of E. coli. If your bleeding started suddenly alongside diarrhea, cramping, nausea, or fever, a foodborne illness is a likely explanation. Most cases resolve within a few days, though some require treatment.
Inflammatory Bowel Disease
Ulcerative colitis causes chronic inflammation in the large intestine and is one of the more significant causes of ongoing bloody stools. Mild cases might mean fewer than four loose bowel movements a day with occasional blood. Severe flares can involve more than six bloody bowel movements daily. In the most extreme cases, people experience more than ten bloody episodes in a single day. The bleeding comes from ulcers that develop in the inflamed colon lining.
If your rectal bleeding keeps coming back, is accompanied by persistent diarrhea, or you’re noticing mucus in your stool alongside abdominal cramping, inflammatory bowel disease is worth investigating. It’s a chronic condition, but it’s very manageable with the right treatment plan.
When Bleeding Could Signal Cancer
Colorectal cancer can cause rectal bleeding, and it’s the possibility most people are worried about when they search this topic. The reassuring reality is that most rectal bleeding, especially in younger adults, is not cancer. But some accompanying symptoms warrant prompt attention: unexplained weight loss, a persistent change in bowel habits (new constipation, diarrhea, or stools that are noticeably narrower than usual), a feeling that your bowel doesn’t fully empty, ongoing fatigue, or abdominal pain.
Routine colorectal cancer screening is now recommended starting at age 45 for people at average risk, per the U.S. Preventive Services Task Force. If you’re 45 or older and haven’t been screened, rectal bleeding is a good reason to get that process started. If you’re younger than 45 but have a family history of colorectal cancer or are experiencing any of those secondary symptoms, your doctor can determine whether earlier screening makes sense.
Signs You Need Immediate Help
Most rectal bleeding is mild, meaning streaks on toilet paper or small amounts in the bowl, and it doesn’t require an emergency visit. But certain situations call for urgent care. A large volume of blood that doesn’t stop is the most obvious one. Dizziness, lightheadedness, a racing heart, or feeling faint alongside bleeding can indicate you’re losing enough blood to affect your circulation. Vomiting blood (or material that looks like coffee grounds) at the same time as rectal bleeding suggests a serious upper digestive tract bleed and needs emergency attention.
How Doctors Find the Cause
If you see a doctor about rectal bleeding, the evaluation typically starts with a digital rectal exam and a conversation about your symptoms. For a closer look, an anoscopy uses a small, short scope to examine the anal canal itself, which is often enough to spot hemorrhoids or fissures. A sigmoidoscopy or colonoscopy uses a longer, flexible tube with a camera to examine part or all of the colon. This is the most thorough way to identify polyps, inflammation, or other sources of bleeding deeper in the digestive tract.
Preventing the Most Common Causes
Since hemorrhoids, fissures, and straining-related bleeding account for the vast majority of cases, prevention centers on keeping your stools soft and easy to pass. The target is 25 to 30 grams of fiber per day from food, not supplements. Most people fall well short of that. Fruits, vegetables, beans, lentils, whole grains, and oats are reliable sources. Increasing fiber too quickly can cause bloating, so it’s better to ramp up gradually over a week or two.
Staying well-hydrated makes fiber work properly. Without enough water, extra fiber can actually make constipation worse. Avoiding long stretches of sitting on the toilet (put your phone down) reduces pressure on the rectal veins. And when you feel the urge to go, go. Delaying bowel movements leads to harder stools and more straining, which is exactly the cycle that causes bleeding in the first place.