Colorectal Cancer: Symptoms and Signs

Approved by the Cancer.Net Editorial Board, 05/2022

ON THIS PAGE: You will find out more about changes and other things that can signal a problem that may need medical care. Use the menu to see other pages.

It is important to remember that the symptoms and signs of colorectal cancer listed in this section are the same as those of extremely common conditions that are not cancer, such as hemorrhoids and irritable bowel syndrome (IBS). When cancer is suspected, these symptoms usually have begun recently, are severe and long lasting, and change over time. By being alert to the symptoms or signs of colorectal cancer, it may be possible to detect the disease early, when it is most likely to be treated successfully. However, many people with colorectal cancer do not have any symptoms or signs until the disease is advanced, so people need to be screened regularly.

People with colorectal cancer may experience the following symptoms or signs. Symptoms are changes that you can feel in your body. Signs are changes in something measured, like by taking your blood pressure or doing a lab test. Together, symptoms and signs can help describe a medical problem. As mentioned above, it is also possible that the symptoms and signs described below may be caused by a medical condition that is not cancer, especially for the general symptoms of abdominal discomfort, bloating, and irregular bowel movements.

  • A change in bowel habits

  • Diarrhea, constipation, or feeling that the bowel does not empty completely

  • Bright red or very dark blood in the stool

  • Stools that look narrower or thinner than normal

  • Discomfort in the abdomen, including frequent gas pains, bloating, fullness, and cramps

  • Weight loss with no known explanation

  • Constant tiredness or fatigue

  • Unexplained iron-deficiency anemia, which is a low number of red blood cells

Talk with your doctor if any of these symptoms last for several weeks or become more severe. If you are concerned about any changes you experience, please talk with your doctor and ask to schedule a colonoscopy.

Because colorectal cancer can occur in people younger than the recommended screening age and in older people between screenings, anyone at any age who experiences these symptoms should visit a doctor to find out if they should have a colonoscopy.

Your doctor will ask how long and how often you’ve been experiencing the symptoms(s), in addition to other questions. This is to help figure out the cause of the problem, called a diagnosis.

If cancer is diagnosed, relieving symptoms remains an important part of cancer care and treatment. Managing symptoms may also be called palliative care or supportive care. It is often started soon after diagnosis and continued throughout treatment. Be sure to talk with your health care team about the symptoms you experience, including any new symptoms or a change in symptoms.

The next section in this guide is Diagnosis. It explains what tests may be needed to learn more about the cause of the symptoms. Use the menu to choose a different section to read in this guide.