Colorectal cancer may not cause symptoms, particularly at first. Someone can have colon cancer or rectal cancer  and not know it. That’s why every person should get screened starting at age 45. People at higher risk may need to get checked earlier, according to their risk factors.  

Screening (testing for colorectal cancer) is the No. 1 way you can prevent colon cancer and rectal cancer. 

With screening, colorectal cancer is one of the most preventable cancers. Colon cancer and rectal cancer are also highly treatable if caught early. That’s why on-time screening is essential and lifesaving. Screening should begin at age 45. 

Symptoms of colorectal cancer may include: 

Changing bowel habits 

Changing bowel habits may include intermittent or constant diarrhea and/or constipation, a change in the consistency of your stool, or stools that are more narrow than usual.

Persistent abdominal discomfort

Abdominal discomfort may present as cramps, gas, or pain. You may also feel full, bloated, or like your bowel is not completely empty. Nausea and vomiting can also be a symptoms.

Rectal bleeding

Blood in or on your stool is a symptom of rectal cancer and colon cancer. The blood can be bright red, or the stool may be black and tarry or brick red.

Weakness and/or fatigue 

Weakness and/or fatigue may be a sign of colorectal cancer. Weakness and/or fatigure may be accompanied by anemia or a low red blood cell count.

Unexplained weight loss

A loss of weight for no known reason should always be investigated. Nausea and/or vomiting are also possible symptoms.