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The information on this page was reviewed and approved by
Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on March 29, 2021.

Colorectal cancer symptoms

With colorectal cancer, you may not experience noticeable symptoms in the early stages. That’s why it’s important to have regular screening tests, such as a colonoscopy—to detect cancer or precancerous conditions in the colon or rectum as early as possible, even before any symptoms appear. 


When colon or rectal cancer does cause symptoms, these may include:

  • Bowel habit changes
  • Blood in or on the stool (blood may be bright red or make stools look very dark)
  • Bleeding from the rectum (bright red)
  • Diarrhea
  • Constipation
  • Incomplete bowel movements (the feeling of being unable to empty your bowel completely)
  • Abnormally narrow stools
  • Stomach pains, bloating, fullness or cramps that occur frequently and don’t go away
  • Unexplained and unintentional weight loss
  • Fatigue
  • Weakness
  • Nausea or vomiting

Over time, if colorectal cancer spreads, other signs and symptoms may arise in different ways or in other parts of the body. For example, blood loss via stool may eventually diminish the number of red blood cells in the body, resulting in anemia, which can sometimes even be the first marked sign of colon cancer via a blood test.


Similarly, colorectal cancer that metastasizes from the digestive tract to organs or tissues in other areas may cause different symptoms depending on the location. If the cancer spreads to your liver, it may cause swelling there, as well as yellowing of the skin or eyes (jaundice). If it spreads to the lungs, it may cause difficulty breathing. 


What to do if you’re experiencing colorectal cancer symptoms


If you’re experiencing symptoms associated with colorectal cancer, you shouldn’t assume you have cancer. Other causes may include infections, hemorrhoids, irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD). Still, visit your doctor to determine the cause of any symptoms and whether treatment is needed.


IBD as a colorectal cancer risk factor

Many potential symptoms of colorectal cancer—such as belly pain, blood in stools and diarrhea—are also common symptoms of IBD (ulcerative colitis or Crohn's disease), making diagnosis particularly tricky. 


However, having IBD raises your risk of developing colorectal cancer. So it’s especially important that IBD patients undergo screenings. 


If you have IBD, you may begin colon cancer screenings at a younger age or need more frequent testing. Discuss your risk and a screening plan with your doctor.

Other colorectal cancer risk factors

Besides having IBD, other factors that may increase your risk of getting colorectal cancer range from race (African Americans have higher rates of colorectal cancer than all other racial groups in the United States) to heredity to habits. This means you can control some factors and try to manage others. 


Modifiable and non-modifiable risk factors for colorectal cancer include:

  • Lack of physical activity
  • Excess weight or obesity
  • Type 2 diabetes
  • Cigarette smoking
  • Moderate or heavy alcohol consumption (three or more drinks daily)
  • Certain inherited syndromes, such as Lynch syndrome or familial adenomatous polyposis
  • Personal history of cancer or high-risk polyps in your colon or rectum
  • Family history of the disease
  • Diet
  • Age (risk increases with age)