Rectal bleeding is the passage of blood from the anus, either mixed with stool, coating the surface of stool, or appearing on its own in the toilet bowl or on toilet paper. It’s one of the most common gastrointestinal symptoms, affecting roughly 15 out of every 1,000 adults over age 34 each year. Most cases trace back to something benign like hemorrhoids or a small tear in the anal lining, but the symptom can also signal conditions that need medical attention.
What the Color of the Blood Tells You
The color of blood you see is one of the most useful clues about where the bleeding is coming from. Bright red blood typically means the source is low in your digestive tract: the colon, rectum, or anus. This is the most common type people notice, and it’s medically called hematochezia. Dark red or maroon blood usually points to bleeding higher up in the colon or in the small intestine, where the blood has had more time to break down before it exits.
Black, tarry stools (called melena) generally indicate bleeding in the stomach, such as from an ulcer. The blood turns dark because it’s been partially digested during its long transit through the intestines. One important exception: very rapid bleeding from an upper source like a stomach ulcer can move through the digestive tract so quickly that it still appears red when it comes out. That’s why the color is a useful starting point but not a definitive diagnosis on its own.
The Most Common Causes
Hemorrhoids
Hemorrhoids are swollen blood vessels in the rectum or anus and are the single most frequent cause of rectal bleeding. Internal hemorrhoids typically cause painless bright red blood on the toilet paper or dripping into the bowl. You might not feel them at all. External hemorrhoids tend to cause a duller ache, pressure, or irritation, and they can become suddenly and severely painful if a blood clot forms inside them (a thrombosed hemorrhoid).
Anal Fissures
An anal fissure is a small tear in the lining of the anus, usually caused by passing a hard or large stool. The bleeding looks similar to hemorrhoids (bright red on toilet paper), but the pain is distinctly different. People with fissures describe a sharp, searing, or tearing sensation during a bowel movement, sometimes compared to passing shards of glass. This intense pain is often followed by a deep ache lasting minutes to hours afterward. That pain pattern is what most reliably distinguishes a fissure from a hemorrhoid.
Diverticular Bleeding
Diverticula are small pouches that form in the wall of the colon, most often in people over 50. They’re usually harmless, but when a blood vessel near one of these pouches erodes, it can cause sudden, painless, and sometimes heavy bleeding. Right-sided diverticular bleeding tends to produce darker, maroon-colored blood, while left-sided sources are more likely to look bright red. The bleeding often stops on its own but can be alarming because of the volume.
Inflammatory Bowel Disease
Ulcerative colitis and Crohn’s disease both cause chronic inflammation in the digestive tract that can lead to rectal bleeding. These conditions typically come with other symptoms too: persistent diarrhea, abdominal cramping, fatigue, and unintended weight loss. The bleeding tends to be ongoing or recurrent rather than a one-time event.
Rectal Bleeding and Cancer Risk
This is the concern most people are really searching about, and the numbers can help put it in perspective. Among adults over 34 who see a doctor for rectal bleeding, about 3.4% are ultimately diagnosed with colorectal cancer. That risk isn’t evenly distributed by age. For people 60 and older, the figure rises to about 5.2%. For those under 60, it drops to 1.8%. So while colorectal cancer is a real possibility, it accounts for a small fraction of rectal bleeding cases overall.
Certain patterns raise more concern: bleeding that persists for weeks, a change in bowel habits (like new constipation or narrower stools), unexplained weight loss, or a family history of colorectal cancer. If you’re over 45 and haven’t had a screening colonoscopy, new rectal bleeding is a good reason to get one scheduled.
How Doctors Evaluate Rectal Bleeding
Evaluation usually starts simple and escalates based on what the initial exam reveals. A digital rectal exam, where a doctor uses a lubricated gloved finger to feel for abnormalities in the anus and lower rectum, is typically the first step. This alone can identify hemorrhoids, fissures, or masses near the anal opening.
If the source isn’t obvious, an anoscopy may follow. This involves inserting a short, rigid tube a few inches into the anus to get a direct view of the anal canal and lower rectum. It’s done in the office and takes only a few minutes. For bleeding that suggests a source higher in the colon, or in anyone with risk factors for colorectal cancer, a full colonoscopy is the standard next step. This examines the entire length of the colon and allows the doctor to take tissue samples or even treat certain bleeding sources during the same procedure.
In cases of heavy, active bleeding where the source can’t be pinpointed with a scope, CT angiography (a specialized scan that highlights blood vessels) can locate the bleeding site.
Hemorrhoids vs. Fissures: A Quick Comparison
- Pain quality: Hemorrhoids cause a dull ache or pressure that can linger all day. Fissures cause sharp, tearing pain specifically during and immediately after a bowel movement.
- Bleeding pattern: Both produce bright red blood on toilet paper. Hemorrhoid bleeding is usually painless (especially internal ones). Fissure bleeding comes with that unmistakable sharp pain.
- Triggers: Hemorrhoids are worsened by prolonged sitting, straining, and pregnancy. Fissures are most often triggered by constipation and hard stools.
When Rectal Bleeding Is an Emergency
Most rectal bleeding is not an emergency, but some situations require immediate medical attention. Call emergency services if you’re experiencing significant bleeding along with any signs of shock: rapid or shallow breathing, dizziness or lightheadedness when you stand up, confusion, fainting, blurred vision, nausea, cold and clammy skin, or very low urine output. These signs suggest you’re losing enough blood to affect your circulation.
You should also get to an emergency room if the bleeding is continuous or heavy (soaking through pads or filling the toilet bowl), or if it’s accompanied by severe abdominal pain or cramping. Heavy bleeding combined with vomiting blood is particularly concerning, as it suggests a rapidly bleeding source in the upper digestive tract.
Managing Minor Rectal Bleeding at Home
When hemorrhoids or fissures are the cause, most episodes resolve with basic self-care. Increasing fiber intake through foods or a supplement softens stools and reduces the straining that worsens both conditions. Drinking more water works alongside fiber to keep stools easier to pass. Warm sitz baths (sitting in a few inches of warm water for 10 to 15 minutes) soothe irritated tissue and can help fissures heal.
Over-the-counter topical creams or suppositories can ease hemorrhoid discomfort, and avoiding prolonged sitting on the toilet reduces pressure on rectal blood vessels. Most hemorrhoids and fissures improve within a few weeks with these measures. If bleeding continues beyond that, or if it returns frequently, it’s worth getting an evaluation to rule out other causes and discuss more targeted treatment options.