What screening tests are used to detect colorectal cancer?

There are several tests used to detect colorectal cancer:

  • Colonoscopy is the gold standard test for detecting colorectal cancer. If everything is normal with this test, people may not need to be tested again for up to 10 years. This test has more serious complications than the other tests, if complications occur.
  • The fecal immunochemical test (FIT) looks for very small amounts of blood in the stool and this can be done every one to two years.
  • A new stool test looks for cancerous DNA and only needs to be done every three years.

In general, starting at age 50, everyone should be screened for colorectal cancer. 

Dr. Daniel Labow, MD
Surgical Oncologist

The most important screening test for colon cancer is a colonoscopy. Other tests can be done that could indicate colon or rectal cancer, but a full colonoscopy is the gold standard. If you cannot tolerate a colonoscopy, Barium enema or “Virtual” colonoscopy can be done, but these tests are less specific and if a biopsy is needed, then the colonoscopy needs to be performed anyway. In an average risk patient, first colonoscopy should be done at age 50, if the patient doesn’t have any symptoms. Any symptoms such as bleeding, change in bowel habits, unexplained weight loss, etc., should prompt a visit to your doctor for evaluation.

The following screening tests can be used to detect polyps, cancer or other abnormal areas. Your doctor can explain more about each test:

  • Fecal occult blood test (FOBT): Sometimes cancers or polyps bleed, and the FOBT can detect tiny amounts of blood in your stool. If this test detects blood, other tests are needed to find the source of the blood. Benign conditions (such as hemorrhoids) also can cause blood in your stool.
  • Sigmoidoscopy: Your doctor checks inside your rectum and the lower part of the colon with a lighted tube called a sigmoidoscope. If polyps are found, your doctor removes them. The procedure to remove polyps is called a polypectomy.
  • Colonoscopy: Your doctor examines inside the rectum and entire colon using a long, lighted tube called a colonoscope. Your doctor removes polyps that may be found.
  • Double-contrast barium enema: You are given an enema with a barium solution, and air is pumped into your rectum. Several x-ray pictures are taken of your colon and rectum. The barium and air help your colon and rectum show up on the pictures. Polyps or tumors may show up.
  • Digital rectal exam: A rectal exam is often part of a routine physical examination. Your doctor inserts a lubricated, gloved finger into your rectum to feel for abnormal areas.
  • Virtual colonoscopy: This method is under study.

This answer is based on source information from National Cancer Institute.

Dr. Mehmet Oz, MD
Cardiologist (Heart Specialist)

There are alternatives to colonoscopy, but they are less likely to prevent cancer compared with the invasive tests: guaiac-based fecal occult blood testing (gFOBT), fecal immunochemical testing (FIT) and stool DNA testing (sDNA), barium enema and computed tomography (CT) colonography. Still, most doctors will recommend colonoscopy to screen for colorectal cancer. (A sigmoidoscopy is a similar tool but only visualizes the first third of the colon.)

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Tests for screening for colorectal cancer are the following: fecal occult blood, flexible sigmoidoscopy, colonoscopy, barium enema, virtual barium enema colonoscopy. Each of these will need to be followed by a biopsy to definitively diagnose the lesion as cancer.

To find polyps or early cancer, healthcare providers may suggest one or more tests for colorectal cancer screening:
  • Flexible sigmoidoscopy
  • Colonoscopy
  • Double-contrast barium enema
  • CT colonography (virtual colonoscopy)
  • Fecal occult blood test (FOBT)
  • Digital rectal exam, which is often part of a routine physical examination

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.