How does Cologuard work?

Every day the lining of your colon naturally sheds cells. If you have cancer or precancer in your colon, abnormal cells shed into the colon – along with normal cells – where they are picked up by stool as it passes through.

Cologuard uses advanced stool DNA technology to find elevated levels of altered DNA and/or hemoglobin in these abnormal cells, which could be associated with cancer or precancer.

How is a sample collected?

The Cologuard Collection Kit is easy to use, and it’s shipped directly to your home. You collect a single stool sample using this kit, then send it to Exact Sciences Labs via prepaid UPS shipping or pick-up. We provide the result back to your doctor, who will contact you to discuss next steps. 

For more on collecting a sample, watch the How To Use video below.

Patients should not provide a sample if they have diarrhea or blood in their urine or stool (for example, bleeding hemorrhoids, bleeding cuts or wounds on their hands, rectal bleeding, or menstruation).

Patients should be advised of the caution listed in the Cologuard Patient Guide. Patients should NOT drink the preservative liquid.

The risks related to using the Cologuard collection kits are low, with no serious adverse events reported among people in a clinical trial. Patients should be careful when opening and closing the lids to avoid the risk of hand strain.

What are the risks and precautions associated with Cologuard?

Cologuard is not for everyone. It is not a replacement for diagnostic or surveillance colonoscopy in high-risk individuals. It may not be right for you if:

  • You have a personal history of colon cancer, polyps, or other related cancers
  • You have a family history of colon cancer
  • You have had a positive result for another screening method in the last six months
  • You have been diagnosed with a condition that places you at high risk for colon cancer. These include but are not limited to: Inflammatory Bowel Disease, Chronic ulcerative colitis, Crohn’s disease, Familial adenomatous polyposis
  • You have been diagnosed with a relevant cancer syndrome passed on from your family, such as Hereditary non-polyposis colorectal cancer syndrome, Peutz-Jeghers Syndrome, MYH-Associated Polyposis, Gardner’s syndrome, Turcot’s (or Crail’s) syndrome, Cowden’s syndrome, Juvenile Polyposis, Cronkhite-Canada syndrome, Neurofibromatosis, or Familial Hyperplastic Polyposis
  • Results should be interpreted with caution for individuals over age 75, as the rate of false positives increases with age

Cologuard may produce false positive or false negative results.

  • A false positive occurs when Cologuard produces a positive result, even though a colonoscopy will not find cancer or precancer. Any positive result should be followed by diagnostic colonoscopy.
  • A false negative occurs when Cologuard does not detect colon cancer or precancer even when a colonoscopy identifies the positive result. Following a negative result, patients should continue participating in a screening program at an interval and with a method appropriate for the individual patient.

Cologuard performance when used for repeat testing has not been evaluated or established.

Next Section: How Effective Is Cologuard? »