Blood when you poop is usually caused by something minor and treatable, most commonly hemorrhoids or a small tear in the skin around your anus. That said, the color, amount, and any symptoms that come with it can tell you a lot about what’s going on and whether you need to act quickly.
The Most Common Causes
Three conditions account for the vast majority of rectal bleeding in adults: hemorrhoids, anal fissures, and constipation-related straining. All three are linked, since straining during a bowel movement can both cause hemorrhoids and tear the delicate tissue around the anus.
Hemorrhoids are swollen veins in or around the rectum. They often cause painless bleeding, which is why you might see bright red blood on the toilet paper or in the bowl without feeling much discomfort. Some people notice itching or mild soreness, but many hemorrhoids produce no pain at all.
Anal fissures are small tears in the lining of the anal canal. Unlike hemorrhoids, fissures tend to hurt, sometimes sharply, right when you’re passing a stool. The pain can linger afterward, and you’ll typically see a streak of bright red blood on the stool or when you wipe. Hard, dry stools are the usual culprit.
Constipation itself deserves mention because it’s often the underlying trigger. When stools are hard and you have to push to pass them, the pressure can injure tissue and make existing hemorrhoids worse.
Less Common but Important Causes
When bleeding isn’t explained by hemorrhoids or a fissure, several other conditions come into play. Diverticulosis, where small pouches form in the wall of the colon, can bleed suddenly and sometimes heavily, often without pain. Inflammatory bowel diseases like ulcerative colitis and Crohn’s disease cause ongoing inflammation that damages the intestinal lining, leading to bleeding that tends to come with other symptoms: diarrhea (often bloody, with mucus or pus), cramping, an urgent need to use the bathroom, fatigue, and unintended weight loss. In the mildest form of ulcerative colitis, where only the rectum is inflamed, rectal bleeding or urgency may be the only noticeable sign.
Colorectal cancer is a less common cause of blood in the stool, but it’s the one most people worry about. The risk increases with age, which is why the U.S. Preventive Services Task Force recommends colorectal cancer screening for all average-risk adults starting at age 45.
What the Color of Blood Tells You
The shade of blood you see gives a rough indication of where the bleeding is happening in your digestive tract.
- Bright red blood typically means the source is low, in the rectum or anus. This is what you’ll see with hemorrhoids, fissures, or rectal inflammation.
- Dark red or maroon blood mixed into the stool suggests bleeding higher up in the colon or small intestine, as with diverticulosis or inflammatory bowel disease.
- Black, tarry stool often points to bleeding in the stomach. Blood that travels the full length of the digestive tract gets digested along the way, turning dark and sticky.
One thing to keep in mind: certain foods and supplements can mimic these colors. Iron supplements and bismuth (the active ingredient in some stomach medications) can turn stool black. Beets can make it look reddish. If you’ve recently eaten or taken something that could explain the color, that’s worth considering before you panic.
Medications That Increase Bleeding Risk
If you take blood thinners (anticoagulants), gastrointestinal bleeding is a recognized side effect. These medications don’t cause the underlying problem, but they can make a small bleed much more noticeable or harder to stop. Anti-inflammatory painkillers like ibuprofen and aspirin can also irritate the stomach lining over time, potentially leading to bleeding higher in the digestive tract. If you’re on any of these and notice blood in your stool, that’s worth bringing up with your doctor promptly, since the bleeding may be unmasking a condition that needs attention.
How to Prevent Straining-Related Bleeding
Since the most common causes of rectal bleeding are tied to constipation and straining, softening your stools is the single most effective thing you can do. The key is fiber and water, working together.
Most adults fall well short of the recommended daily fiber intake: 25 to 30 grams per day for women and 30 to 38 grams for men. You can get there through fruits, vegetables, beans, whole grains, and seeds. If your current diet is low in fiber, increase gradually over a couple of weeks rather than all at once, since a sudden jump can cause bloating and gas. As you add fiber, increase your water intake at the same time. Fiber absorbs water to bulk up and soften stool, so without enough fluid, it can actually make constipation worse.
Avoiding long periods of sitting on the toilet also helps. Scrolling your phone for 15 minutes while sitting puts steady pressure on the veins around the rectum, which is a recipe for hemorrhoids.
Signs That Need Immediate Attention
A small amount of bright red blood on the toilet paper after a hard bowel movement, especially if it happens once and resolves, is usually not an emergency. But certain combinations of symptoms signal something more serious.
Go to an emergency room if rectal bleeding is continuous, heavy, or accompanied by severe abdominal pain or cramping. Call 911 if you’re also experiencing rapid or shallow breathing, dizziness or lightheadedness when you stand up, blurred vision, fainting, confusion, nausea, cold or clammy skin, or very low urine output. These are signs of significant blood loss that needs treatment right away.
Even when bleeding is mild, certain patterns should prompt a doctor visit relatively soon: bleeding that recurs over days or weeks, a change in your bowel habits that lasts more than a few weeks, blood mixed into the stool rather than just on the surface, dark or tarry stools, or bleeding paired with unexplained weight loss, fatigue, or persistent abdominal pain. These symptoms overlap with conditions like inflammatory bowel disease and colorectal cancer that benefit from early diagnosis.
What Happens at the Doctor’s Office
If you go in for rectal bleeding, expect the visit to focus on narrowing down the source. Your doctor will ask about the color and amount of blood, how long it’s been happening, your bowel habits, diet, medications, and family history of colon problems. A physical exam of the area can often identify hemorrhoids or fissures on the spot.
If the cause isn’t obvious or the bleeding pattern raises concerns, a colonoscopy is the standard next step. This lets a doctor examine the entire colon directly and, if needed, take tissue samples. For people with lower-risk symptoms, a more limited exam that looks only at the lower portion of the colon may be sufficient. The goal is straightforward: find where the blood is coming from and rule out anything that needs treatment beyond dietary changes and time.