Common Stool Changes That Could Be A Sign of Colon Cancer

Changes in your stool (poop) can sometimes be the first sign of colon cancer. Colon cancer is one of the most common causes of death from cancer in the U.S. But it’s treatable when caught early.

Most people don’t have stool changes in early stages of colon cancer. In fact, early colon cancer doesn’t cause any symptoms, which is why screening is so important. But it’s still good to know what to look for and what to do if you notice any symptoms.

What stool changes may be a sign of colon cancer?

Colon cancer can affect your colon in different ways. It can lead to narrowing of your colon, bleeding, and make it harder for your body to absorb nutrients. Sometimes, these changes can affect your stool, leading to:

• Black or bloody stools

• Stool that’s thin (like a pencil), flat, or ribbon-like

• New diarrhea (loose stools) or constipation that doesn’t go away 

• Changes in how often you have a bowel movement

Keep in mind that having these changes doesn’t automatically mean you have colon cancer. But if you develop any of them, it’s important to notify your healthcare professional so they can diagnose the underlying cause.

Other symptoms associated with colon cancer

Stool changes aren’t the only possible symptoms of colon cancer. Here are some other signs and symptoms to watch out for:

• Unintentional weight loss 

• Abdominal pain

• Fatigue

• Anemia

It’s important to know that most people with colon cancer don’t have symptoms at first. People can go a long time without knowing cancer is in their colon. This is why screening for colon cancer is so important.

How do you screen for colon cancer?

For most people, colon cancer screening should start at the age of 45. There are many different screening tests available, including:

• Fecal immunochemical test (FIT) test: Checks for blood in your stool

• DNA stool test: Checks your stool for DNA (genetic material) from cancerous or precancerous cells

• Colonoscopy: A procedure that uses a long, flexible tube with a camera to look inside your entire colon (requires bowel prep and sedation) 

• Sigmoidoscopy: Similar to a colonoscopy, but only looks at the bottom of your colon (sedation usually isn’t required)

• Virtual colonoscopy (or CT colonography): Uses a CT scan to take pictures of the colon to see if there are any unusual changes that may suggest cancer

EXPERT PICKS: WHAT TO READ NEXT

• Colon cancer in young adults: Learn why more people under age 50 are getting colon cancer and the best way to protect yourself. 

• Living with colon cancer: Read about how paying attention to early symptoms helped one man beat colon cancer. 

• Colon cancer risk factors: From your genes to your diet, learn about the main factors that increase your risk for colon cancer.

Your doctor can help you find the best option for you based on your symptoms, medical history, and risk factors (if any).

Do only people with stool changes need to be checked for colon cancer?

Definitely not. People with early colon cancer don’t usually have stool changes or any other symptoms. This is why it’s important to get the recommended colon cancer screening starting at age 45 (or earlier if you have risk factors).

You shouldn’t wait until you have symptoms to get screened. But if you notice stool changes or other symptoms, make sure you get medical attention right away.

Do only people with a family history get colon cancer?

No. Colon cancer can happen to anyone. Over 75% of all new colon cancers happen in people who don’t have a family history of it. If you do have a family history of colon cancer, you may need to start screening for colon cancer before the age of 45. And you may need to do it more frequently.

Which other conditions can cause changes to the stool like colon cancer?

There are other conditions that can cause bloody stool or changes in the size or frequency of stool. These include:

• Infection (like Clostridiodes difficile (C. diff) colitis)

• Diverticulitis

• Inflammatory bowel disease (like Crohn’s disease or ulcerative colitis)

• Hemorrhoids

It can sometimes be hard to know what’s causing stool changes. If you’re having symptoms, speak with your healthcare professional about appropriate testing.

When to get medical attention for stool changes

If you have any changes in your stool or bowel habits, you should talk to your healthcare professional. They’ll use your medical history, a physical exam, and lab tests to look for the source of the changes. If your symptoms are concerning for colon cancer or you have risk factors, they may recommend a screening test.

Frequently asked questions

Why trust our experts?

Written by:

Valerie Emuakhagbon, MD

Valerie Emuakhagbon, MD, is a board-certified colorectal surgeon. A native of Dallas, Texas, she completed the six-year BA/MD program at the University of Missouri-Kansas City.

Edited by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. A pulmonologist and hospitalist, she practiced and taught clinical medicine at hospitals in London for a decade before entering a career in health education and technology.

Reviewed by:

Maria Robinson, MD, MBA

Maria Robinson, MD, MBA, is a board-certified dermatologist and dermatopathologist who has practiced dermatology and dermatopathology for over 10 years across private practice, academic, and telehealth settings. She is a fellow of the American Academy of Dermatology and the American Society of Dermatopathology.

Our editorial standards

Meet our experts