Colon Cancer Screenings: Types of Tests + Testing Guidelines

Colorectal cancer screening tests are routine tests used to detect early signs of colon cancer. Screening tests help healthcare providers catch cancers in their early stages, hopefully before they can spread and worsen. Early detection can make it easier to treat cancer if treatment is needed.

Both the American Cancer Society (ACS) and the United States Preventative Services Task Force (USPSTF) recommend that adults with an average risk of colon cancer start regular screening at the age of 45. This article will detail colon cancer risk factors, the different types of screenings available to you, and general colorectal screening recommendations.

Risk factors for colorectal cancer

Colorectal (colon and rectal) cancer risk is not the same for everyone. Your personal and family medical history, lifestyle habits, and certain medical conditions can affect how likely you are to develop this disease. Most people fall into the average-risk category, meaning they do not have specific risk factors that significantly raise their chances above the general population.

You are typically at "average risk" for colon (colorectal) cancer if you meet the following criteria:

• You do not have a personal history of colon cancer or certain types of colon polyps.
• You do not have inflammatory bowel diseases like Crohn’s disease or ulcerative colitis.
• You do not have a strong family history of colon cancer (for example, a parent, sibling, or child diagnosed—especially at a young age).
• You do not have a known inherited genetic condition that increases colon cancer risk (such as Lynch syndrome or familial adenomatous polyposis).

It's important to note that being “average risk” does not mean “no risk.” Colon cancer is common; in 2025, it was the fourth most common cancer in the U.S.. That's why routine screening is recommended even for people at average risk.

If you are at an increased risk of colon or rectal cancer, you may need to test more frequently.

You may be at high risk of colorectal cancer if:

• You have a family history of colorectal cancer
• You have a personal history of ovarian cancer
• You have a history of inflammatory bowel disease (like Crohn’s disease or ulcerative colitis)
• You have been diagnosed with familial adenomatous polyposis, Lynch syndrome, or adenomas (noncancerous polyps)
• A personal history of radiation therapy to the abdomen or pelvis to treat cancer
• You drink more than 3 alcoholic beverages per day
• You smoke cigarettes
• You have obesity

Types of colorectal cancer screening tests

There are several different types of screening options for colon cancer: stool-based tests, colonoscopies, virtual colonoscopies, and sigmoidoscopies. You can learn more about each of these options below.

Stool-based tests

Stool tests check a stool (feces) sample for signs of cancer. They can often be performed at home with a test kit and are less invasive than a colonoscopy. However, they may need to be performed more often, and a colonoscopy will still be required to diagnose cancer or polyps.

The three most common types of stool-based tests include:

1. Stool DNA tests (sDNA): Stool DNA tests (available in the United States under the brand name Cologuard) check for the presence of abnormal cells and blood in a stool sample. Cancer or polyp cells have DNA mutations in certain genes. Cologuard screens for these changes and blood in the stool to indicate the possible presence of cancer or polyps.

You will need to undergo a colonoscopy if the test results are positive (meaning genetic mutations or blood are found in the stool sample).

2. Fecal immunochemical tests (FIT): FIT tests check stool samples for the presence of blood. They do not require any food or drug restrictions before taking the test. If evidence of blood is found in the stool, you will need to undergo a colonoscopy to determine the cause of the bleeding.

3. Guaiac-based fecal occult blood tests (gFOBT or FOBT): These tests check a stool sample for blood. Small stool samples are collected and applied to a special card. A chemical is then placed on the sample. If the card changes color, it may indicate the presence of hidden (occult) blood in the stool.

FOBT tests cannot determine whether blood in the stool is from the colon or other parts of the digestive tract. If the test finds traces of blood, you will need to undergo a colonoscopy to determine the exact cause of the bleeding.

Certain foods and medications can affect FOBT test results. If you are taking one of these tests, your provider may recommend that you avoid the following before testing:

• NSAIDs (ibuprofen, naproxen, or aspirin), red meat, vitamin C, can cause colorectal bleeding, which may lead to a false-positive result.
• Red meat: Certain substances in red meat (beef, lamb, or liver) can lead to a false-positive test result. You may be asked to avoid eating red meat for 3-7 days before testing.
• Vitamin C: Vitamin C from supplements, fruit juices, or citrus fruits can lead to a false-negative result (a result that doesn’t show traces of blood when there may be some). You may be asked to avoid consuming vitamin C for 3-7 days before testing.
• Other foods such as beets, broccoli, turnips, radishes, horseradish, artichokes, mushrooms, cauliflower, apples, oranges, bananas, grapes, and melon can also cause false positive tests.

Colonoscopy

A colonoscopy is a visual examination of the entire colon and rectum. To do this, providers use a small camera attached to a flexible tube (a device called a colonoscope) that is inserted into the anus. These tests are performed in a procedure room at your healthcare provider’s office or as an outpatient procedure at a hospital.

Here’s what to expect during a colonoscopy:

• You will be asked to remove your clothes and change into a hospital gown.
• You will be given medicine via an IV to help with sedation (relaxation). You may be awake during the procedure, but you shouldn’t feel pain during it.
• Your provider will ask you to lie on your side with your knees pulled up to your chest.
• The scope is gently inserted into the anus and is moved into the large intestine.
• Small instruments may be passed through the scope to collect suspicious tissue (biopsy) or remove polyps.

Your bowels need to be clear during this procedure. To achieve this, your provider may ask you to take steps such as:

• Use enemas for several days before your test
• Avoid eating for 1-3 days before the test
• Use laxatives, if necessary, for several days before the test

In addition to detecting the signs of colon cancer, colonoscopies are used to find signs of:

• Colitis (inflammation in the intestines caused by inflammatory bowel diseases like Crohn’s disease or ulcerative colitis)
• Abnormalities in the intestine (known as diverticulitis)
• Polyps

Virtual colonoscopy

Virtual colonoscopies (also known as CT colonography) are X-rays taken in a CT machine to create a three-dimensional picture of the colon and rectum. This test may be performed as a follow-up to stool samples.

While CT colonography is less invasive than a colonoscopy, these tests do not allow providers to collect tissue samples (biopsies). Because of this, your provider may elect to perform a regular colonoscopy over a CT scan.

Sigmoidoscopy

Sigmoidoscopy (also known as flexible sigmoidoscopy) is not widely used in the United States, as this test can only examine a fraction of the colon. Sigmoidoscopy doesn’t require anesthesia but still requires colon prep.

Recommendations for colorectal screenings

Both the American Cancer Society (ACS) and the US Preventive Services Task Force (USPSTF) recommend that adults with an average risk of colon cancer start regular screening at the age of 45. This should continue through the age of 75.

After this, the decision to screen for colorectal cancer is based on the individual’s risk factors, life expectancy, screening history, and personal preferences. The ACS advises against colorectal cancer screening in people over 85.

If you are at high risk for colon cancer (you have a family history of colorectal cancer, personal history of polyps, or inflammatory bowel disease), you may need to start screening earlier than 45, and you may need to be screed more frequently. Your health care provider can recommend the best screening schedule for you.

Talk to your provider about colorectal screening

Colorectal cancer screenings are crucial for the early detection of colon cancer. Catching cancer early can make it easier to treat. Talk to your provider about the benefits and risks of colorectal screenings and the screening schedule that is best for you based on your health history.