Colorectal Cancer Screening: Tests, Guidelines, Ages & Prevention

What Is Colorectal Cancer Screening?

Colorectal cancer screening means testing people who have no symptoms for colorectal cancer or for polyps that could become cancer. Most colorectal cancers start as small growths called polyps in the lining of the colon or rectum, and they usually take years to turn into cancer. Screening works in two ways: it can prevent cancer by finding and removing polyps before they change, and it can detect cancer early, when it is far more treatable. Colon cancer and rectal cancer are grouped together as colorectal cancer because they share the same screening tests.

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Colorectal Cancer Screening Tests Compared

National guidelines accept several screening tests. They fall into two groups: stool-based tests you do at home, and visual exams that look directly at the colon and rectum. The USPSTF intervals for people at average risk are:

• FIT (fecal immunochemical test): a home stool test for hidden blood, repeated every year.
• High-sensitivity guaiac stool test (gFOBT): an older home test for hidden blood, repeated every year.
• Multitarget stool DNA test (FIT-DNA, such as Cologuard): checks stool for blood and abnormal DNA, repeated every 1 to 3 years.
• Colonoscopy: a visual exam of the entire colon, repeated every 10 years if normal. Polyps can be removed during the same exam.
• CT colonography (virtual colonoscopy): an X-ray scan of the colon, repeated every 5 years.
• Flexible sigmoidoscopy: a visual exam of the rectum and lower colon, repeated every 5 years, or every 10 years when combined with a yearly FIT.

An abnormal result on any test other than colonoscopy should be followed by a colonoscopy. A stool test or CT scan can suggest a problem, but only colonoscopy can confirm it and remove polyps. Screening is only complete once that follow-up colonoscopy is done.

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Colorectal Cancer Screening Guidelines by Age

• Ages 45 to 75: the USPSTF (2021), the American Cancer Society and the ACG all recommend regular screening for adults at average risk. The starting age was lowered from 50 to 45 because colorectal cancer has been rising in younger adults.
• Ages 76 to 85: screening is an individual decision based on your overall health, life expectancy and past screening results. Talk it through with your doctor.
• Over 85: routine screening is generally no longer recommended.

These age ranges apply to people at average risk, meaning no personal history of colorectal cancer or advanced polyps, no inflammatory bowel disease, no inherited cancer syndrome and no strong family history. If any of those apply, the schedule is different (see below).

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Who Needs Earlier or More Frequent Screening?

• Family history: if a parent, sibling or child had colorectal cancer or an advanced polyp, screening with colonoscopy often starts at age 40, or 10 years before the age at which that relative was diagnosed, whichever comes first.
• Inherited syndromes: people with Lynch syndrome or familial adenomatous polyposis (FAP) may need colonoscopy starting in their 20s or earlier, under specialist guidance.
• Inflammatory bowel disease: long-standing ulcerative colitis or Crohn's colitis usually calls for surveillance colonoscopy starting about 8 years after diagnosis.
• Previous polyps or colorectal cancer: follow-up colonoscopy is scheduled based on what was found, rather than the standard 10-year interval.
• Prior radiation to the abdomen or pelvis for a childhood cancer may also call for earlier screening.

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Screening vs. Diagnostic Testing: When You Have Symptoms

Screening schedules are for people without symptoms. If you have any of the following, do not wait for your next screening date. See a doctor, who may order a diagnostic colonoscopy:

• Rectal bleeding or blood in the stool
• A change in bowel habits (diarrhea, constipation or narrower stools) lasting more than a few weeks
• Unexplained weight loss
• Iron-deficiency anemia or ongoing fatigue
• Persistent abdominal pain or cramping

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Does Insurance Cover Colorectal Cancer Screening?

Under the Affordable Care Act, most private health plans must cover USPSTF-recommended colorectal cancer screening for adults 45 to 75 without a copay or deductible. Federal guidance also says a follow-up colonoscopy after a positive stool-based test counts as part of screening. Medicare Part B covers screening colonoscopy and stool-based tests, and since 2023 it also covers the follow-up colonoscopy after a positive stool test as screening. Coverage details differ by plan, and billing can change if a colonoscopy is done because of symptoms rather than for screening, so check with your insurer before your appointment.

Colonoscopy: The Most Complete Screening Test

Colonoscopy is the only screening test that can both find and remove polyps in the same visit, and it examines the whole colon. A normal colonoscopy at average risk means you usually do not need another for 10 years. It does require a bowel preparation the day before and sedation, so you will need a ride home. Learn more about colonoscopy and what a colonoscopy can detect, including polyps.

How to Choose the Right Screening Test

Experts agree that the best screening test is the one you actually complete. Stool tests are easy and done at home but must be repeated every 1 to 3 years, and a positive result leads to a colonoscopy. Colonoscopy is more involved on the day but covers 10 years if normal. The ACG names colonoscopy and yearly FIT as the primary screening options for most average-risk adults. Your doctor can help you weigh your risk, preferences and insurance coverage.

How to Lower Your Colorectal Cancer Risk

Screening is the most effective way to prevent colorectal cancer, but daily habits also matter. The American Cancer Society links these steps to a lower risk:

• Stay physically active and keep a healthy body weight.
• Eat plenty of vegetables, fruit and whole grains, and limit red and processed meats.
• Avoid smoking, and limit or avoid alcohol.
• Know your family history and share it with your doctor, since it can change when you start screening.

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Common Screening Myths

A few misunderstandings keep people from getting screened:

• "I feel fine, so I don't need it." Most early colorectal cancers and polyps cause no symptoms. That is exactly why screening exists.
• "No one in my family had it." Most people diagnosed with colorectal cancer have no family history of the disease.
• "A stool test replaces colonoscopy forever." Stool tests are valid screening options, but they must be repeated on schedule, and any positive result needs a colonoscopy.

Colorectal Screening Resources

• Colonoscopy: how the procedure works
• What a colonoscopy detects: polyps and more
• Colonoscopy prep instructions
• Colon cancer screening in Katy & Cypress, TX

Getting Screened in the Greater Houston Area

If you live in west or northwest Houston, United Gastroenterology Associates offers screening and diagnostic colonoscopy at two offices: our Katy gastroenterology office and our Cypress gastroenterology office. For appointment details, insurance and what to expect locally, see our colon cancer screening in Katy and Cypress page.

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Sources and Guidelines

• U.S. Preventive Services Task Force. Colorectal Cancer: Screening (2021).
• American Cancer Society. Guideline for Colorectal Cancer Screening.
• Centers for Disease Control and Prevention. Colorectal Cancer Screening.
• Shaukat A, et al. ACG Clinical Guidelines: Colorectal Cancer Screening 2021. Am J Gastroenterol.
• Medicare.gov. Colorectal Cancer Screenings.

Colorectal Cancer Screening FAQs

Is colon cancer screening the same as colorectal cancer screening?
Yes. The same tests screen for cancer of the colon and the rectum, so the terms are used interchangeably.

Is a stool test as good as a colonoscopy?
Both are guideline-approved. Stool tests are less invasive but must be repeated more often and cannot remove polyps. Colonoscopy finds and removes polyps in one visit.

What happens if my FIT or Cologuard result is positive?
You will need a follow-up colonoscopy. A positive stool test does not mean you have cancer, but it must be checked.

Is there a blood test for colorectal cancer screening?
An FDA-approved blood test became available in 2024 for average-risk adults 45 and older. It is not currently part of USPSTF recommendations and is not considered a substitute for colonoscopy or stool tests for people willing to do them.

When can I stop screening?
For most people, after age 75 the decision is individual, and screening is generally not recommended after 85.