Colon cancer is associated with symptoms that most people have experienced at one time or another, such as diarrhea, constipation or fatigue. These common symptoms become worrisome when they persist or are associated with more specific signs of colon cancer, such as bloody bowel movements and bleeding from the rectum. If you experience this combination of symptoms, you should follow up with your medical care provider. Early detection is key to the healthiest possible outcome for people with warning signs and symptoms of colon cancer.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.

Bloody Stools

Blood on or mixed with bowel movements, or stools, is the most common sign of colon cancer. This blood may be dark or bright red. It can also be mixed with mucus. If you notice blood in your stools, your doctor will order a laboratory analysis called a fecal occult blood test.

Rectal Bleeding

Bleeding from the rectum occurs in more than half of people with colon cancer, according to an article published in the July 2009 issue of "BMC Medicine." Blood is often bright red. It may color the toilet bowl water or stain toilet paper. The passage of blood may coincide with painful bowel movements. A new pattern to rectal symptoms in someone with hemorrhoids should prompt medical follow-up.


Blood loss from colon cancer can result in anemia, a shortage of red blood cells or hemoglobin in the blood. You may feel constantly tired, weak or short of breath. Your skin may be pale.

Abdominal Pain

Abdominal discomfort, gas, cramping, bloating and pain are common symptoms in people who are later diagnosed with colon cancer.

Weight Loss

Colon cancer can cause unexplained weight loss even though you are eating as usual. Or, you may lose all appetite for food. According to the July 2009 "BMC Medicine" article, more than a third of people with colon cancer experience unexplained weight loss.


Constipation that persists more than a few days also may occur in association with colon cancer. Chronic, or ongoing, constipation may even increase your risk of developing colon cancer 5.

Changes in Stools

Bleeding from colon cancer can cause the passage of dark, tar-like stools. They may be black or maroon in color. They may seem sticky. Normal bowel movements may alternate with these dark stools. Some colon cancers, by growing in the intestinal wall, decrease stool caliber. Stools can become very narrow or ribbon-like. In some cases, the stool may only be as large in diameter as a pencil.


Changes in the colon from cancer can cause persistent diarrhea. According to the "BMC Medicine" article, more than 1 in 5 people with colon cancer will experience diarrhea.

Nausea and Vomiting

Unexplained, persistent nausea and vomiting may be symptoms of colon cancer. You may experience these with or without other abdominal symptoms.

Trouble Passing Stool

Changes in bowel evacuation can occur with colon cancer. There may be a sensation of incomplete passing of stool. Others may have the sensation of urgently needing to have a bowel movement or to strain, but no stool is passed.