Colorectal Cancer: Symptoms and Signs

Approved by the Cancer.Net Editorial Board, 09/2023

ON THIS PAGE: You will find out more about the changes and medical problems that can be a sign of colorectal cancer. Use the menu to see other pages.

What are the symptoms and signs of colorectal cancer?

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 one or more of the following symptoms or signs. Symptoms are changes that you can feel in your body. Signs are changes in something measured, like 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 try to understand what is causing your symptom(s). They may do an exam and order tests to understand the cause of the problem, which is 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 and supportive care,” which is not the same as hospice care given at the end of life. This type of care focuses on managing symptoms and supporting people who face serious illnesses, such as cancer. You can receive palliative and supportive care at any time during cancer treatment. Learn more in this guide’s section on Coping with 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.