7 Tests to Screen for Colorectal Cancer

This blood test requires a blood draw from your arm; then the sample is sent to a lab for evaluation. The blood test is for people at average risk for colon cancer and those who don’t have a family history of the disease or previous polyps, according to the ACS. 

It’s important to note that, unlike a colonoscopy, the blood test will not detect precancerous polyps. What’s more, a positive result is not a diagnosis; it’s an indication that a colonoscopy is needed to confirm whether cancer is present.

“The way we are approaching blood tests for colon cancer screening is more a complementary option to colonoscopy, or for individuals who may be at higher risk for anesthesia issues and may not be a suitable candidate for an invasive procedure,” says Ekta Gupta, M.D., chief of gastroenterology at University of Maryland Medical Center Midtown in Baltimore.

Gupta emphasizes the importance of weighing the pros and cons of each test with your doctor, and says any test a patient is willing to get is better than none.

The blood-based screening test is covered under Medicare Part B once every three years for average-risk individuals who meet the screening criteria. If you have private insurance, check with your plan. The test’s manufacturer stated in 2024 that it expects commercial insurance coverage to expand “following anticipated future guideline inclusion by the American Cancer Society and the U.S. Preventive Services Task Force (USPSTF).”

3. Virtual colonoscopy

Computed tomography (CT) colonography — sometimes called a virtual colonoscopy — uses X-rays to produce pictures of the colon for your doctor to analyze. This requires your health care provider to put a small tube in your rectum to add air into the colon and make it easier to see. 

You will need to do the same bowel prep as a traditional colonoscopy, but you won’t need sedation. The limitation to this procedure is that it can detect polyps that are 10 millimeters and larger, Gupta explains.

If the colonography detects a polyp or another suspicious area, you’ll need a colonoscopy to remove it. If your test is negative, your doctor will likely ask you to repeat it once every five years.

4. Sigmoidoscopy

This procedure gives your doctor a look at only part of your colon (the lower third), so it may be used if you have unexplained symptoms in your lower colon, rectum or anus. Because it doesn’t check your entire colon, it’s not widely used to screen for colorectal cancer, says the National Institute of Diabetes and Digestive and Kidney Diseases. According to ACS, at least 4 out of 10 colorectal cancers start in the upper portion (right side) of the colon.

This test isn’t as invasive as a colonoscopy and doesn’t require sedation for people who cannot tolerate sedation. It does, however, require the same bowel prep as a colonoscopy does, and it comes with risks of bleeding, pain and perforation. This test is done every five years.

Home-based stool tests

There are at-home options for screening for people who can’t or won’t undergo a colonoscopy and are at average risk for colorectal cancer. These tests — which require a stool sample that is later analyzed at a lab — are noninvasive but are more likely to generate incorrect results: False-positive results mean your test indicates you have colon cancer when there is no evidence of it, and false-negative results mean your test indicates you don’t have cancer when you actually might.  

If anything suspicious appears on the test, your doctor will recommend a colonoscopy.

5. Guaiac-based fecal occult blood test (gFOBT)

This test uses a chemical called guaiac to detect microscopic amounts of blood in the stool. Gupta says this test is not used as often as other screening tools, because more accurate tests are available. (One study found gFOBT has approximately a 50 percent sensitivity in detecting cancer; others have noted different ranges.)

Plus, the gFOBT requires the patient to avoid taking anti-inflammatory drugs like ibuprofen or aspirin for a week before testing and high amounts of vitamin C for three days before testing. Patients must also avoid certain foods, like red meat, melon, radishes, horseradish, and turnips. Additionally, the gFOBT requires three separate stool samples. The test should be done annually, the ACS says.

6. Fecal immunochemical test (FIT)

The FIT uses antibodies to detect blood in the stool from the lower intestines. Unlike the gFOBT, this test has no drug or dietary restrictions and is less likely to react to bleeding from the upper parts of the digestive tract, the ACS says. The CDC recommends repeating this test annually.

7. Stool DNA or RNA tests

The FIT-DNA test, also called the stool DNA test, combines the FIT with a test that detects abnormal DNA in the stool that could indicate the presence of cancer or a polyp. According to the USPTF, this test is more sensitive than FIT alone, but it may result in false-positive results. If you choose this test (called Cologuard), it should be repeated every three years, the CDC says.

In 2024, the FDA approved a new RNA-based stool test, called ColoSense, which detects RNA changes and blood in the stool. Because the product is new, insurance coverage may be spotty, so check with your plan about costs.

Editor's note: This story, first published May 1, 2025, has been updated to reflect a change in Medicare coverage for computed tomography (CT) colonography.