Colorectal Cancer Test: Which Test Is Right for You?

Written By: Theresa Vuskovich, DMD

Colorectal cancer (CRC) is the third most common cancer and the third most common cause of cancer-related deaths in the United States, but early detection can save lives.^1–3 CRC screening tests can detect CRC before symptoms develop.^4–7 When CRC is detected early, your healthcare provider has a better chance of treating it successfully.

Thanks to advancements in CRC screening tests, early detection of CRC is easier than ever. However, with so many options available, choosing the best CRC screening test can be challenging.

Choosing the Right Colorectal Cancer Test

According to a recent study published in the Journal of the American Medical Association, approximately 60 million Americans with an average risk of CRC need a CRC screening test.⁹ Before choosing a test, it's important to remember that CRC screening tests are for asymptomatic patients. If you have bloody stools, bowel changes, iron-deficiency anemia, or unexplained abdominal pain, contact your healthcare provider about the best steps to follow.⁶

Finding the ideal test for you requires weighing the benefits and risks along with balancing practical aspects of testing, including traveling for procedures and paying for tests. Though most health insurance pays for CRC screening tests, your insurance may not cover other tests to diagnose CRC. Consult with your insurance company to verify your coverage.¹⁰

CRC screening tests are categorized as visual, stool, or blood-based.⁵ Tests are also classified as 1-step or 2-step.⁵ While colonoscopies (visual, 1-step) remain the gold standard of CRC screening tests, colonoscopies are unpleasant, time-consuming, and invasive. New technology uses stool and blood to look for clues (i.e., biomarkers) rather than directly visualizing the cancer, making it easier to test for CRC.

Stool and blood-based tests have varying levels of sensitivity (how well the test can detect if a person has the disease) and specificity (how well the test can detect if someone does not have the disease). However, all tests discussed in this article are FDA-approved as CRC screening tests. There are other tests available to test your risk of cancer. These tests include polygenic risk score (PRS) and multi-cancer early detection (MCED) tests. While PRS and MCED tests can provide valuable insights, they are not FDA-approved screening tests.

Now that you know more about the basics of CRC screening tests, let's walk through each test type so you know what to expect. We'll discuss the pros and cons of each option and how to prepare.^{4–7,10–13}

Visual (In-Office)

Colonoscopy

A colonoscopy is a procedure performed by a gastroenterologist who uses a camera to see your colon, detect cancer, collect tissue samples, and remove precancerous growths (polyps) called adenomas. A colonoscopy is the gold standard for these reasons, as it enables your healthcare provider to not only detect CRC but also diagnose CRC and treat precancerous growths. This makes colonoscopies a 1-step CRC screening test.

While colonoscopies require prepping for the procedure (bowel clean-out), fasting, sedation, and traveling, colonoscopies are generally only recommended every ten years for individuals with an average risk of CRC. Colonoscopies are a great choice if you prefer a one-step test and less frequent screenings. Colonoscopy is also the ideal screening test for everyone at increased risk of CRC.

Flexible Sigmoidoscopy

A flexible sigmoidoscopy is a procedure performed by a healthcare provider who uses a camera to visualize the colon. This procedure only examines the rectum and the last part of the colon.

A flexible sigmoidoscopy requires fasting, sedation, and travel, but a flexible sigmoidoscopy is less invasive than a colonoscopy. Flexible sigmoidoscopies are recommended every five to ten years if you are at average risk for CRC.

Virtual Colonoscopy

A virtual colonoscopy is also called a computed tomography (CT) colonography. During a virtual colonoscopy, your healthcare provider will use a CT scanner to visualize your colon and detect the presence of cancer.

Though a virtual colonoscopy provides a less invasive way to visualize CRC, your healthcare provider can't remove polyps or take a biopsy, so you may need a follow-up colonoscopy. The test also requires fasting and reliable transportation. Virtual colonoscopies are generally recommended every five years.

Stool (At-Home)

Fecal Immunochemical Test (FIT or iFOBT)

A FIT uses antibodies to detect if blood is present in one's stool, but it does not tell you if you have CRC. A positive FIT indicates that you need additional testing for CRC, making a FIT a 2-step CRC screening test. A FIT is a non-invasive test and doesn't require fasting. A FIT offered by Everlywell requires participants to use a brush to apply water from the toilet bowl to a card (not the stool sample itself).

While fasting is unnecessary for a FIT, certain foods or drugs, such as aspirin, ibuprofen, red meats, and vitamin C supplements, can affect your results. Remember to discuss medication changes with a healthcare provider. Also, it is best to wait before testing if you're bleeding from hemorrhoids, menstruating, experiencing blood in your urine, recovering from GI surgery, or experiencing a diverticulitis flare. These conditions can create a false positive result. If negative, a FIT test is recommended once a year.

Guaiac Fecal Occult Blood Test (gFOBT)

A gFOBT detects small amounts of blood in stool and can detect blood further in the GI tract. The gFOBT uses a substance called guaiac, a plant-derived chemical, that binds to hemoglobin (a protein in your blood). Completing a gFOBT requires collecting stool samples over three separate days. The samples are smeared onto a card and sent to a lab.

Fasting is also not necessary for a gFOBT. However, you may need to change your diet. Avoiding red meat, raw vegetables, medications to stop diarrhea, Vitamin C supplements, and iron is advised three days before your test. Similar to the FIT, you may receive a false positive if you are experiencing hemorrhoids, menstruating, or experiencing a diverticulitis flare. If negative, a gFOBT is generally recommended once a year.

Multitarget Stool DNA Testing (sDNA-FIT)

A sDNA-FIT (Cologuard®) detects blood and DNA biomarkers in your stool. A sDNA-FIT requires a prescription from your healthcare provider. During a sDNA-FIT, you will place a complete bowel movement into a container and ship it to a laboratory. Fasting and altering your diet are not necessary for a sDNA-FIT. If negative, a sDNA-FIT is recommended every three years.

Blood (In-Office)

Shield™ Liquid Biopsy

Shield™ is the first blood-based, FDA-approved CRC screening test. This test uses cell-free DNA (cfDNA) in your blood to detect circulating tumor DNA (ctDNA). While a Shield™ test doesn't require fasting or preparation, this test does require a prescription from a healthcare provider, and it is not the best test for people who are scared of needles. Your healthcare provider will collect a vial of blood and ship the sample to a laboratory for processing. A colonoscopy is required to confirm CRC if you have a positive Shield™ result. Talk to your healthcare provider about how often to undergo blood-based CRC screening tests.

You Should Start Screening at Age 45

Screening for CRC begins at age 45 for average-risk Americans, and the decision to continue screening after age 75 requires a talk with your healthcare provider.^4–7 When it comes to CRC screening, 45 is the new 50. In 2021, the United States Preventive Services Task Force (USPSTF) lowered the recommended age for starting CRC screening to 45.⁴ Yet, many people are unaware of the new guidelines and rising rates of CRC among younger adults.

Everlywell published its State of Stool Stigma Survey results in 2024, revealing common misunderstandings about CRC. The survey of 1,000 Americans aged 18–55+ found most people are unaware that CRC is now the leading cause of cancer-related deaths among men under 50.² Awareness, education, and early detection are key to reducing CRC cases. So, it's best to spread the word about colorectal cancer screening, converse with your coworkers, familiarize your family, and share information about CRC with your friends.

Discovering Your Colorectal Cancer Risk

The USPSTF recommends starting CRC screening tests at age 45 for Americans with an average risk of CRC. But how do you know if you have an average risk of CRC? You have an average risk of colorectal cancer if you can answer no to all of the following questions:^6–8

• Do you have a history of colorectal cancer or precancerous polyps?
• Do you have a family history of colorectal cancer or precancerous colorectal polyps?
• Do you or your family have a history of syndromes associated with colorectal cancer? (Some syndromes associated with an increased risk of CRC include familial adenomatous polyposis, Lynch syndrome, cystic fibrosis, Peutz-Jeghers syndrome, Cowden syndrome, Li-Fraumeni syndrome, Juvenile polyposis syndrome, or MUTYH-associated polyposis)
• Do you have inflammatory bowel disease (ulcerative colitis or Crohn's disease)?
• Do you have a history of abdominal radiation for childhood cancer?

Answering yes to any of the questions above means you have an increased risk of CRC. As a result, your healthcare provider may recommend starting CRC screening tests earlier, choosing a specific test, and scheduling tests more often.^7,8 However, most Americans have an average risk of developing CRC.

While a family history of CRC increases your risk of CRC, lifestyle factors often play a larger role. Risk factors such as obesity, diabetes, cigarette smoking, and excessive alcohol use can increase your CRC risk.⁴ Yet, 75% of Americans believe family history is the biggest risk factor for colon cancer, according to the State of Stool Stigma Survey. Fortunately, family history plays a smaller role in CRC development, meaning you can lower your risk by eating a balanced diet, exercising regularly, drinking responsibly, and staying up-to-date with screening.

Accessing Personalized Care With Everlywell

Navigating the healthcare system can be tricky, but Everlywell offers virtual care visits to guide you. During a virtual care visit, you can discuss your health concerns and receive a customized plan to reach your goals. Everlywell provides tailored care wherever you go so you can live your best life.

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2. American Cancer Society. Colorectal Cancer Facts & Figures 2023–2025. Atlanta: American Cancer Society; 2023. Accessed February 9, 2025. https://www.cancer.org/content/dam/cancer-org/research/cancer-facts-and-statistics/colorectal-cancer-facts-and-figures/colorectal-cancer-facts-and-figures-2023.pdf
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6. National Comprehensive Cancer Network. Guidelines for Patients: Colorectal Cancer Screening. Accessed February 2, 2025. https://www.nccn.org/guidelines/guidelines-detail?category=2&id=1429
7. Doubeni C, Elmore J, et al. Screening for colorectal cancer: strategies in patients at average risk. In: Connor RF, ed. UpToDate. Waltham, MA: UpToDate; 2020. Accessed February 9, 2025. https://www.uptodate.com/contents/screening-for-colorectal-cancer-strategies-in-patients-at-average-risk
8. Weiss JM, Gupta S, Burke CA, et al. NCCN Guidelines® Insights: Genetic/Familial High-Risk Assessment: Colorectal, Version 1.2021. J Natl Compr Canc Netw. 2021;19(10):1122–1132. doi:10.6004/jnccn.2021.0047. https://pubmed.ncbi.nlm.nih.gov/34666312/
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13. Guardant Health. Shield™ Colorectal Cancer Screening Test Provider Brochure. Accessed February 9, 2025. https://shieldcancerscreen.com/wp-content/uploads/LBL-000351-R1-Shield-Provider-Labeling.pdf