Colorectal Cancer Signs and Symptoms

Colorectal cancer might not cause symptoms right away, but if it does, it may cause one or more of these symptoms.

Common signs and symptoms of colorectal cancer

• A change in bowel habits, such as diarrhea, constipation, or narrowing of the stool, that lasts for more than a few days
• A feeling that you need to have a bowel movement that’s not relieved by having one
• Rectal bleeding with bright red blood
• Blood in the stool, which might make the stool look dark brown or black
• Cramping or abdominal (belly) pain
• Weakness and fatigue
• Unintended weight loss

Colorectal cancers can often bleed into the digestive tract. Sometimes the blood can be seen in the stool or make it look darker, but often the stool looks normal. But over time, the blood loss can build up and can lead to low red blood cell counts (anemia). Sometimes the first sign of colorectal cancer is a blood test showing a low red blood cell count.

Signs of colorectal cancer that has spread

Some people may have signs that the cancer has spread to the liver with a large liver felt on exam, jaundice (yellowing of the skin or whites of the eyes), or trouble breathing from cancer spread to the lungs.  

Do colon polyps cause symptoms?

Most people with polyps will not have any symptoms. However, some people may have symptoms from polyps, such as:

• Bleeding from the rectum
• Change in stool color, either red or black
• Change in bowel movement, either prolonged constipation or diarrhea
• Low red blood cell count due to low iron (iron deficiency anemia)
• Abdominal (belly) pain

These symptoms can also be due to other causes, such as foods, medicines, or other medical conditions. If these symptoms are present, you should discuss further with your doctor.

If you have signs or symptoms

Many of these symptoms can be caused by conditions other than colorectal cancer, such as infection, hemorrhoids, or irritable bowel syndrome. Still, if you have any of these problems, it’s important to see your doctor right away so the cause can be found and treated, if needed. See Tests to Diagnose Colorectal Cancer.