Seeing blood when you pass gas is almost always caused by a source of bleeding somewhere in the lower digestive tract, most commonly hemorrhoids or a small tear in the lining of the anal canal. The act of farting itself doesn’t cause bleeding, but the pressure of pushing gas through the rectum and anus can disturb tissue that is already irritated, inflamed, or fragile. The blood typically shows up as a bright red streak on toilet paper or a few drops in the bowl, and while the sight can be alarming, the explanation is usually something treatable and not life-threatening.
Hemorrhoids and Anal Fissures Are the Usual Suspects
Hemorrhoids are swollen blood vessels in and around the anus. Internal hemorrhoids sit just inside the rectum where you can’t feel them, but they bleed easily when anything pushes past them, whether that’s a bowel movement or a forceful burst of gas. The blood is typically bright red and painless. External hemorrhoids, which sit under the skin around the anal opening, are more likely to cause discomfort or itching. A 2025 review in JAMA notes that the first-line approach for all hemorrhoidal disease involves increasing dietary fiber and water intake and avoiding straining during bowel movements.1JAMA. Hemorrhoidal Disease: A Review That straining piece matters here: if you tend to bear down hard on the toilet, you’re putting repeated pressure on the same vessels that then bleed when gas passes through later.
Anal fissures are tiny tears in the skin lining the anus, usually caused by passing a hard or large stool. They tend to produce a sharp, stinging pain during and after a bowel movement, along with bright red blood. Once a fissure exists, even something as minor as a strong fart can reopen it or irritate it enough to produce a small amount of blood. Standard treatment includes fiber supplementation, adequate fluids, and topical medications that relax the muscle around the fissure to let it heal.2Diseases of the Colon & Rectum. The Effect of Nonoperative Management of Chronic Anal Fissure and Hemorrhoid Disease on Bowel Function Patient-Reported Outcomes
What the Color of the Blood Tells You
Blood color is one of the most useful clues for figuring out where bleeding is coming from. Bright red blood almost always points to the lower end of the digestive tract: the rectum, anus, or the last portion of the colon. The brighter and fresher it looks, the closer to the exit it originated. A study that tested patients’ ability to identify stool color found that when patients pointed to the brightest red shades on a color card, the bleeding source was in the colon, rectum, or anus with very high reliability.3PubMed. An objective measure of stool color for differentiating upper from lower gastrointestinal bleeding
Dark red or maroon blood suggests a source higher up in the colon. Black, tarry stools, sometimes described as looking like coffee grounds, point to the upper digestive tract, such as the stomach or the first part of the small intestine. Blood that has traveled a long distance through the gut gets digested along the way, which turns it dark. In the same study, when patients identified the darkest (black) color on the card, the positive predictive value for an upper gastrointestinal source was extremely high, at 0.95.3PubMed. An objective measure of stool color for differentiating upper from lower gastrointestinal bleeding So if the blood you see while farting is bright red and limited to a small amount, the source is very likely local. If it’s dark or mixed into stool that looks tarry, the situation warrants faster medical attention.
Diverticular Disease
Diverticula are small pouches that form in the wall of the colon, usually in the lower left portion. They’re extremely common in adults over fifty and usually cause no symptoms at all. But occasionally, a blood vessel running alongside one of these pouches erodes and starts bleeding. Diverticular bleeding tends to be painless and can be heavy, producing a noticeable amount of blood in the toilet. Fewer than five percent of people with diverticulosis ever experience this kind of bleeding, and it often stops on its own.4PubMed Central. Management of Diverticular Bleeding: Evaluation, Stabilization, Intervention, and Recurrence of Bleeding and Indications for Resection after Control of Bleeding
If diverticular bleeding is behind the blood you see when passing gas, you’d typically notice it’s more than just a smear. The bleeding presents as a large volume of lower gastrointestinal bleeding rather than a few drops on the tissue. Anyone experiencing this kind of volume should head to an emergency department rather than wait for a scheduled appointment.
Inflammatory and Infectious Causes
Conditions that cause ongoing inflammation in the rectum or colon can make the lining fragile enough to bleed with minimal provocation, including the mechanical stress of passing gas. Ulcerative colitis, a form of inflammatory bowel disease, commonly involves the rectum and produces blood and mucus mixed with stool. Crohn’s disease can affect any part of the digestive tract and may also cause rectal bleeding, though its symptoms tend to be more variable.
Radiation proctitis is another inflammatory cause that people often don’t think of. It can develop weeks to years after pelvic radiation therapy for cancers of the prostate, cervix, or rectum. The main symptoms include diarrhea, urgency, and rectal bleeding.5Thieme Connect (Endoscopy). Argon plasma coagulation in chronic radiation proctitis If you’ve had pelvic radiation in the past and notice blood when passing gas or having bowel movements, radiation proctitis is a realistic possibility worth raising with your doctor.
Infections of the rectum can also produce bleeding. Infectious proctitis most often occurs in people with a history of receptive anal exposure and is frequently caused by organisms like gonorrhea, chlamydia, herpes simplex virus, or syphilis.6PubMed Central. Infectious proctitis: what every gastroenterologist needs to know The bleeding in these cases usually comes with additional symptoms like discharge, pain, and a feeling of needing to use the bathroom urgently. These infections are treatable with antibiotics or antivirals once properly diagnosed, but they won’t resolve on their own.
Less Common Structural Causes
Two less familiar conditions deserve mention because they produce symptoms that can be confusing and are often misdiagnosed for a long time.
Solitary rectal ulcer syndrome is a chronic condition where one or more ulcers form on the rectal wall, typically from prolonged excessive straining or abnormal defecation patterns. Symptoms include rectal bleeding, heavy mucus discharge, a persistent feeling of incomplete evacuation, and sometimes rectal prolapse.7PubMed Central. Solitary rectal ulcer syndrome: clinical features, pathophysiology, diagnosis and treatment strategies This condition is most commonly recognized in young adults, but it also occurs in children, where it tends to be underdiagnosed.8PubMed Central. Solitary rectal ulcer syndrome in children: a literature review If you spend a long time straining on the toilet and notice blood along with mucus when you pass gas or have a bowel movement, this condition is worth investigating.
Angiodysplasia refers to abnormal clusters of blood vessels in the wall of the colon or rectum. These malformed vessels lack the normal smooth muscle layer that gives blood vessels their strength, which makes them prone to rupturing under mechanical stress.9Frontiers in Medicine. Angiodysplasia as a rare cause of acute hematochezia in a 33-year-old with vascular risk factors: a case report Angiodysplasia is more common in older adults, particularly those with conditions that affect blood vessel health, but rare cases have been documented in younger people. The bleeding can range from subtle spotting to sudden heavy blood loss, and the condition is usually found during colonoscopy.
Blood-Thinning Medications Can Make Things Worse
If you’re already taking a blood thinner and start noticing blood when you fart, the medication may not be the cause, but it’s almost certainly making the bleeding more noticeable or harder for your body to stop. A study of elderly patients presenting to an emergency department with rectal bleeding found that more than half were taking some form of anticoagulant or antiplatelet medication. Among those patients, direct oral anticoagulants were the most common, followed by aspirin, clopidogrel, and warfarin.10PubMed Central. Management of blood thinning medications in elderly populations presenting with rectal bleeding: Are we doing right? The most common underlying cause in that group was diverticulosis.
This doesn’t mean blood thinners cause rectal bleeding from scratch. What they do is amplify bleeding from a source that might otherwise stop quickly on its own. A hemorrhoid that would have oozed a single drop could produce enough blood to notice in the toilet bowl. A small fissure that would have sealed itself in minutes might keep oozing for hours. If you take any anticoagulant or antiplatelet medication and notice new or increased rectal bleeding, don’t stop the medication on your own. Call your prescribing doctor, because they need to weigh the bleeding risk against whatever condition the medication is treating.
When the Blood Isn’t From Something Benign
The overwhelming majority of cases of blood noticed while passing gas trace back to hemorrhoids, fissures, or other non-cancerous causes. But colorectal cancer and rectal polyps can also produce bleeding, and they can mimic the symptoms of hemorrhoids closely enough that people dismiss them. Rectal bleeding that persists for more than a couple of weeks, bleeding accompanied by a change in your bowel habits, unexplained weight loss, or a new feeling that your bowels aren’t emptying completely all warrant investigation regardless of your age.
A common diagnostic mistake is assuming that bright red blood automatically means the bleeding is from the very end of the digestive tract and skipping a full exam of the colon. Research comparing diagnostic approaches found that starting with a full colonoscopy rather than just looking at the lower portion of the colon is more effective, safer, and less costly, even when the blood appears bright red.11The American Journal of Gastroenterology. Comparison of the color of fecal blood with the anatomical location of gastrointestinal bleeding lesions: potential misdiagnosis using only flexible sigmoidoscopy for bright red blood per rectum That finding matters because some people and their doctors may settle for a limited exam when a more thorough one is needed to rule out problems higher in the colon.
Why People Put Off Getting Checked
It’s one thing to know you should see a doctor about rectal bleeding. It’s another to actually do it. A cross-sectional study of people with hemorrhoid symptoms found that the most frequently reported barriers to seeking care were embarrassment and fear of invasive diagnostic procedures. Specifically, about four in ten respondents cited colonoscopy as a major deterrent, and nearly the same proportion said the same about a digital rectal exam.12PubMed Central. Barriers to Seeking Medical Care for Hemorrhoidal Symptoms: A Cross-Sectional Observational Study
That reluctance is understandable but comes with real costs. Hemorrhoids and fissures that go untreated for months or years can worsen and eventually require procedures that are more involved than what would have been needed early on. And in the small percentage of cases where rectal bleeding signals something more serious, delays in diagnosis make outcomes meaningfully worse. If the sight of blood when you pass gas has been happening for more than a week or two, or if the amount seems to be increasing, a visit to your doctor is the single most useful thing you can do. Most of the time, you’ll leave with reassurance and a straightforward plan. Occasionally, you’ll catch something that genuinely needed catching.
Practical Steps to Reduce Irritation
If your bleeding is from hemorrhoids or fissures, the things that help are unglamorous but effective. Increasing fiber intake, either through food or a supplement, softens stool and reduces the strain that damages tissue in the first place. Drinking enough water matters because fiber without adequate fluid can actually make constipation worse. Avoiding prolonged sitting on the toilet, which many people do while scrolling their phones, reduces the sustained pressure on anal blood vessels.
Warm sitz baths, where you sit in a few inches of warm water for ten to fifteen minutes, can relieve discomfort and improve blood flow to the area, which helps healing. Over-the-counter creams and suppositories containing hydrocortisone or witch hazel can ease inflammation and itching in the short term. For anal fissures that don’t heal with these measures, doctors may prescribe topical calcium channel blockers, which relax the internal sphincter and improve blood supply to the tear.2Diseases of the Colon & Rectum. The Effect of Nonoperative Management of Chronic Anal Fissure and Hemorrhoid Disease on Bowel Function Patient-Reported Outcomes
For conditions beyond hemorrhoids and fissures, treatment depends entirely on the underlying cause. Inflammatory bowel disease requires ongoing medical management. Infectious proctitis needs targeted antimicrobials. Angiodysplasia and radiation proctitis may be treated with techniques that seal off the fragile blood vessels during a colonoscopy or sigmoidoscopy. The treatment for radiation proctitis using argon plasma coagulation, for instance, reduces rectal bleeding in roughly eighty to ninety percent of cases.5Thieme Connect (Endoscopy). Argon plasma coagulation in chronic radiation proctitis The common thread across all of these is that none of them get better by being ignored, and most of them respond well to treatment once correctly identified.
Gas Itself and Why It Feels Connected
People often wonder whether the gas itself is somehow causing the bleeding, or whether excessive flatulence is a sign of the same problem. The two aren’t usually related in a direct cause-and-effect way. Gas is a normal byproduct of digestion and bacterial fermentation in the colon. Everyone passes gas, typically over a dozen times a day, and the act of doing so doesn’t damage healthy tissue.
What gas does is create pressure. When you pass a forceful fart, the walls of the rectum and anus briefly stretch and then contract. If there’s already a swollen hemorrhoid sitting in the anal canal, or a healing fissure in the skin, or an inflamed patch of rectal lining, that mechanical disturbance can be enough to produce a bit of bleeding. The gas is the messenger, not the problem. That said, if you’re noticing both an unusual increase in flatulence and blood, the combination can sometimes point to conditions that cause both symptoms simultaneously, such as inflammatory bowel disease, infections, or food intolerances that have led to gut inflammation. In those cases, the gas and the blood share a common upstream cause rather than one triggering the other.