Hemorrhoids or colon cancer? How to tell when bleeding needs a check

Hemorrhoids and colon cancer can both cause bright red blood when you wipe, so the blood itself cannot tell you which one you have. Hemorrhoids are far more common. Still, studies of people who saw a doctor for rectal bleeding find cancer in a small share of them, including some who also had hemorrhoids. If you are worried about bleeding hemorrhoids, the useful question is whether your bleeding needs a closer look.

This page explains how hemorrhoid bleeding usually looks, the warning signs that studies link to colorectal cancer, what the numbers show for adults under 50, and what a doctor will do to sort it out. It is written to help you decide when to book a visit. It cannot tell you that a bleed is harmless.

Why the two get mixed up

Hemorrhoids are cushions of blood vessels inside and around the anus that have swollen or slipped. The most common sign of internal hemorrhoids is bright red blood on the toilet paper, on the stool or in the bowl ¹. That is also the kind of bleeding many people picture when they think of cancer.

The American Cancer Society list of colorectal cancer symptoms includes rectal bleeding with bright red blood, blood in the stool that can make it look dark brown or black, a change in bowel habits that lasts more than a few days, the feeling that you still need to go after a bowel movement, belly cramps or pain, weakness and tiredness, and weight loss you did not plan ². The same page says many of these symptoms can come from other conditions, such as infection, hemorrhoids or irritable bowel syndrome, and that you should still see a doctor right away to find the cause ². It also notes that cancer can bleed slowly while the stool looks normal, and that sometimes the first sign is a blood test showing anemia ².

So the overlap is real. A cancer low in the rectum can bleed bright red, just like a hemorrhoid. A hemorrhoid can also sit alongside a polyp or cancer higher up. Our guide to hemorrhoid symptoms covers the other look-alikes, such as fissures and abscesses.

How hemorrhoid bleeding usually looks

Typical hemorrhoid bleeding has a pattern. It shows up with a bowel movement, it is bright red, and it sits on the paper, on the outside of the stool or drips into the bowl ¹. It often follows straining or a hard stool. There is usually little or no pain, unless you also have a fissure or a clotted external hemorrhoid. Hemorrhoid bleeding rarely causes anemia, which is a low red blood cell count ¹¹.

Some features make a source other than a hemorrhoid more likely. These are the ones studies and cancer groups point to:

A bleed that fits the left column is still worth mentioning to a doctor. A bleed with anything in the right column should not wait for the next routine visit.

What the studies say about bleeding and cancer

How often bleeding turns out to be cancer

In a study from southern England, 604 people with rectal bleeding were referred from their family doctors to a diagnostic clinic. Colorectal cancer was found in 22 of them, which is 3.6% ³. Two things raised the odds. Compared with people under 50, the odds were about 5 times higher at ages 50 to 69 and about 8 times higher at 70 and older. Blood mixed with the stool also raised the odds, by about 4 times after adjusting for other factors ³.

The same study tested the idea that bright red blood with known hemorrhoids is safe to ignore. People with hemorrhoids and bright red blood that was not mixed into the stool did have lower odds of cancer. But cancer was still found in 2% of them ³. The authors concluded that the type of bleeding a patient describes is not reliable enough to decide who needs testing ³.

A systematic review of rectal bleeding in primary care pooled 8 studies with 2,323 patients. On average, about 7% of people who saw a family doctor for rectal bleeding had colorectal cancer, with a range of 3.3% to 15.4% across studies ⁴. Being 60 or older, weight loss and a change in bowel habits raised the chance of cancer. Severe anemia was the strongest single clue, but even then most people with it did not have cancer ⁴. In plain terms, no single symptom sorts people well, which is why doctors lean on an exam and, when needed, a colonoscopy.

Bleeding in adults under 50

Colorectal cancer in younger adults is less common, but it is the group most likely to have bleeding blamed on hemorrhoids. A 2024 meta-analysis of red flag symptoms in early-onset colorectal cancer combined 81 studies of people diagnosed before age 50 ⁵. Rectal bleeding was the most common first symptom, reported by 45% of them. Belly pain was next at 40%, and a change in bowel habits at 27%. Rectal bleeding was linked to at least a 5-fold higher chance of early-onset cancer. On average, diagnosis came 4 to 6 months after the first symptom ⁵.

A large US insurance study looked at 5,075 people diagnosed with colorectal cancer before 50 and compared them with people without cancer ⁶. Four signs in the months before diagnosis were linked to cancer: belly pain, rectal bleeding, diarrhea and iron deficiency anemia. Having one of them roughly doubled the risk. Having two raised it about 3.6 times, and three or more raised it about 6.5 times ⁶.

Records from two New York hospitals show what delay can cost. Among 180 people under 50 who had surgery for colorectal cancer, 94% had symptoms at diagnosis and 59% had bleeding ⁸. The authors noted that evaluation was often delayed and that bleeding was often put down to hemorrhoids. More than half had stage 3 or 4 cancer by the time it was found ⁸.

Do hemorrhoids raise your risk of colon cancer?

Hemorrhoids and colorectal cancer come from different tissue. Hemorrhoids are swollen vascular cushions, while cancer grows from the lining of the colon or rectum. Polyps, which can turn into cancer, often cause painless bleeding and are found with a scope, not by looking at the outside of the anus ¹¹.

One database study from Taiwan followed about 37,000 people with hemorrhoids and the same number without ¹⁰. Colorectal cancer was diagnosed more often in the hemorrhoid group, at 1.29 versus 0.54 cases per 1,000 people per year ¹⁰. When the researchers also matched the groups for colonoscopies and polyps, the cancer rate in the hemorrhoid group came out lower instead, which they put down to overmatching ¹⁰. A study like this shows a link in records. It cannot show that hemorrhoids cause cancer. Part of the link may come from cancer symptoms being recorded as hemorrhoids before the cancer was found. The authors’ practical advice was that people with hemorrhoids, especially those with a positive stool blood test, should be offered a colonoscopy ¹⁰.

When to see a doctor, and how fast

The NIDDK page on hemorrhoid symptoms says to see a doctor if you have any bleeding from the rectum, and if symptoms continue after a week of home care ¹. That advice holds even if you have had hemorrhoids before. Our page on when to see a doctor for hemorrhoids explains which clinician to book and how to prepare.

If you are under 45, the bleeding fits the typical hemorrhoid pattern and you have none of the signs above, a routine appointment is reasonable. Bring a short note of when the bleeding started, how often it happens, what it looks like and any family history. The hemorrhoid symptom checker can help you sort your answers before the visit.

What the doctor will check

The visit starts with questions about your symptoms, bowel habits, diet and medical history ¹². Then comes a look at the outside of the anus and a digital rectal exam, which is a gloved, lubricated finger in the rectum. Many doctors also use an anoscope, a short lighted tube, to see the lining of the anus and lower rectum. It is done in the office and most people do not need anesthesia ¹².

These checks can confirm hemorrhoids, but they only see the last few inches of the bowel. If your age, symptoms or family history call for it, the doctor will order a flexible sigmoidoscopy or a colonoscopy to see higher up ¹². A colonoscopy looks at the whole colon. That matters because in the review of young adults with bleeding, almost a third of the growths were in the upper colon ⁷.

Screening and bleeding are different things

The US Preventive Services Task Force recommendation advises colorectal cancer screening for adults aged 45 to 75 at average risk ⁹. Screening, including home stool tests, is meant for people without symptoms. If you are bleeding, you are no longer in the screening group. Ask your doctor whether you need a diagnostic test instead. If you are 45 or older and have never been screened, raise that at the same visit.

Treating hemorrhoids while you wait for answers

Hemorrhoid care does not hide cancer, so you can start it while you arrange a visit. More fiber is the treatment with the best evidence for bleeding. In a review of seven fiber trials, people taking fiber were about half as likely to keep bleeding ¹³. Our hemorrhoid diet guide shows how to reach a daily target, and our picks of the best fiber supplements for hemorrhoids cover powders and capsules if food alone is hard.

Short toilet sits, no straining and warm soaks help too. Keep track of the bleeding while you try these. If it stops within a week or two and you had no red flags, tell your doctor at the visit anyway. If it keeps going or changes, move the appointment up. How long a typical flare lasts is explained in how long hemorrhoids last.