Colorectal Cancer Screening: Which Test Is Right for You?

What is colorectal cancer screening?

Colorectal cancer screening, which Dr. Khan provides at United Gastroenterology Associates in Cypress and Katy, means checking people who have no symptoms for colorectal cancer or for polyps that could turn into cancer. Most colorectal cancers start as polyps that grow slowly over years, so finding and removing them can prevent cancer, and finding cancer early, before symptoms appear, usually makes treatment more effective. Testing someone who already has symptoms, such as rectal bleeding, is a diagnostic evaluation rather than screening.

What are the current colon cancer screening guidelines?

The U.S. Preventive Services Task Force recommends that adults at average risk begin colorectal cancer screening at age 45 and continue through age 75. Between 76 and 85, screening is an individual decision based on health and prior results. People with a family history of colorectal cancer or advanced polyps, inflammatory bowel disease, certain genetic syndromes, or symptoms such as rectal bleeding may need to start earlier and screen more often, usually with colonoscopy.

Which colon cancer screening tests are available?

Recommended colon cancer screening tests fall into two groups: stool-based tests you do at home, such as the fecal immunochemical test (FIT) and the multitarget stool DNA test (Cologuard), and visual exams, such as colonoscopy, CT colonography and flexible sigmoidoscopy. Any positive stool test or abnormal visual exam other than colonoscopy needs a follow-up colonoscopy to finish screening.

Sensitivity is the share of lesions a test detects when colonoscopy is the reference. Figures come from the studies named and vary by population; a test is only effective if it is repeated on schedule and any abnormal result is followed by colonoscopy.

Is colonoscopy the best colon cancer screening test?

Colonoscopy is the most complete test because it examines the entire colon and allows polyps to be removed during the same procedure, which prevents them from becoming cancer. It is the preferred test for people at higher risk or with symptoms. For average-risk adults, the best test is the one you will actually complete on schedule, so a yearly FIT or a stool DNA test is a good choice for people who prefer to avoid or delay colonoscopy.

What about blood tests for colon cancer screening?

Blood-based tests that look for signs of colorectal cancer in a blood sample are FDA-approved for some average-risk adults age 45 and older. In 2026 the American Cancer Society added blood-based testing to its guideline as a non-preferred option for people who decline or do not complete a colonoscopy or stool-based test, while the American College of Gastroenterology cautioned that these tests detect precancerous polyps and early cancers far less reliably. A positive blood test still requires a colonoscopy, and a negative result does not rule out polyps. Ask Dr. Khan whether a blood test makes sense for you before choosing it over a preferred test.

Colonoscopy vs. FIT: how do they compare?

A FIT (fecal immunochemical test) is an at-home stool test that looks for hidden blood. It needs no bowel preparation or sedation and is repeated every year when normal. A colonoscopy looks directly at the entire colon and rectum and can remove polyps during the same visit; for an average-risk person with a normal result it is usually repeated in about 10 years, but it requires bowel preparation, sedation and a driver. FIT detects most cancers when it is done every year, but it misses many precancerous polyps; colonoscopy finds more polyps but is a procedure with small risks. The American College of Gastroenterology and the U.S. Multi-Society Task Force list colonoscopy every 10 years and annual FIT as first-tier options for average-risk adults. A positive FIT always needs a follow-up colonoscopy, because the stool test cannot show where the bleeding comes from.

Cologuard vs. colonoscopy

Cologuard is a multitarget stool DNA test that combines a FIT with tests for DNA changes shed by cancers and some large polyps. It is done at home and repeated every 1 to 3 years under USPSTF guidance (every 3 years under the test’s labeling). It detects more cancers and advanced polyps than a single FIT, but it also has more false positives, meaning a positive result when colonoscopy finds no cancer or advanced polyp, and it can still miss some polyps and cancers. Cologuard is a screening option for average-risk adults without symptoms. It is not appropriate for people with symptoms, a personal history of polyps or colorectal cancer, inflammatory bowel disease or a strong family history, and in those situations it does not replace colonoscopy. See our comparison of colonoscopy vs. Cologuard.

What if a stool test is positive?

A positive FIT or stool DNA result means blood or abnormal DNA was found in the stool. It does not mean you have cancer: many people with a positive result have polyps, hemorrhoids or no clear cause, and most do not have cancer. The result is only resolved by a colonoscopy, which should be scheduled promptly rather than repeating the stool test. Read what to do after a positive Cologuard test.

Family history and higher risk

Screening often starts earlier, relies on colonoscopy and is repeated more often for people with a parent, sibling or child who had colorectal cancer or advanced polyps; a personal history of polyps or colorectal cancer; ulcerative colitis or Crohn’s disease affecting the colon; an inherited syndrome such as Lynch syndrome or familial adenomatous polyposis; or prior abdominal or pelvic radiation for a childhood cancer. For example, guidance often suggests starting at age 40, or 10 years before the age at which a close relative was diagnosed, whichever is earlier, but your own schedule should be set by a clinician who knows your full history.

Screening vs. diagnostic testing

Screening tests are for people without symptoms. If you have rectal bleeding, black stools, iron-deficiency anemia, a lasting change in bowel habits, unexplained weight loss or ongoing abdominal pain, you need a diagnostic evaluation, usually including a colonoscopy, rather than a home screening test. A diagnostic colonoscopy may also be billed differently from a screening exam. Learn how each type works on our colonoscopy services page.

Screening decisions at ages 76 to 85

Between ages 76 and 85, the USPSTF recommends deciding about screening individually. The balance of benefit and risk depends on your overall health and life expectancy, whether you have been screened before and what earlier results showed, and your own preferences. People who have never been screened are more likely to benefit than those with a history of normal screening. After age 85, routine screening is generally not recommended.

How do you choose the right screening test?

Consider your risk level, whether you are comfortable with bowel prep and sedation, how often you are willing to repeat the test, and your insurance coverage. Average-risk adults can choose any recommended option. People with a strong family history, past polyps, IBD or symptoms should choose colonoscopy. Dr. Khan reviews your history and helps you pick a test you can complete.

Does insurance cover colon cancer screening tests?

Most plans, including Medicare, cover recommended colon cancer screening tests as preventive care for eligible adults. Medicare, for example, covers a screening colonoscopy once every 10 years for people at average risk (or 4 years after a flexible sigmoidoscopy) and every 2 years for people at high risk, and covers a follow-up colonoscopy after a positive Medicare-covered stool or blood test as a screening test; coinsurance can apply if a polyp is removed or a biopsy is taken. Commercial plans vary. A colonoscopy for symptoms may be billed as diagnostic, and facility, anesthesia and pathology charges may apply. See insurance information and screening vs diagnostic colonoscopy.

Where can you get colon cancer screening in Katy or Cypress?

Dr. Muhammad Ali Khan offers screening colonoscopy and guidance on every recommended test for patients from Katy, Cypress, Fulshear, Richmond and Greater Houston. Learn more about our colon cancer screening service, colonoscopy in Katy, colonoscopy in Cypress, colonoscopy vs Cologuard, what to do after a positive Cologuard and how often you need a colonoscopy.

Related reading: who needs colonoscopy screening and how often, how often to repeat a colonoscopy and what it can detect, how colorectal cancer is diagnosed and staged, colonoscopy guide for women and screening at 45, positive stool tests and prep troubleshooting.

Key takeaways

• Average-risk adults should start colon cancer screening at 45 and continue to 75.
• Recommended colon cancer screening tests include colonoscopy, FIT, stool DNA, CT colonography and sigmoidoscopy.
• Any abnormal non-colonoscopy result needs a follow-up colonoscopy.
• Higher-risk adults and anyone with symptoms should have a colonoscopy.
• The best test is one you complete on schedule.

Positive stool tests and blood tests: what to know

What happens if a Cologuard or FIT test comes back positive?

A positive Cologuard or FIT result means the test found hidden blood or abnormal DNA in your stool. It is not a cancer diagnosis. Most people with a positive stool test do not have colorectal cancer: many have precancerous polyps, and some have no significant finding at all.

That last group is a false positive. Stool DNA tests flag more people than FIT, so they produce more false positives. In the BLUE-C study, specificity for advanced neoplasia was 90.6% for the next-generation Cologuard test and 94.8% for FIT, meaning roughly 9 in 100 and 5 in 100 people without advanced lesions, respectively, still received a positive result. The only way to resolve a positive result is a colonoscopy, preferably within 6 months; repeating the stool test does not settle the question.

Under federal Affordable Care Act guidance (FAQs Part 51, January 2022), the follow-up colonoscopy after a positive stool-based screening test is part of the preventive screening process, so most non-grandfathered commercial plans must cover it without cost-sharing for plan years beginning on or after May 31, 2022. Medicare has treated this follow-on colonoscopy as a screening test since January 1, 2023, and since 2025 also after a positive Medicare-covered blood-based test. If a polyp is removed, Medicare coinsurance of up to 15% can still apply through 2026, falling to 10% in 2027 to 2029 and to 0% in 2030. Call (346) 340-4414 to confirm your own benefits.

Can blood tests (cfDNA) replace colonoscopy for cancer screening?

Circulating cell-free DNA (cfDNA) tests, such as Guardant Health’s Shield, look for DNA fragments that tumors shed into the bloodstream. The FDA approved Shield in July 2024 for average-risk adults 45 and older, and the American Cancer Society’s 2026 guideline lists it only for people who decline or do not complete a stool test or colonoscopy.

The key difference is cancer detection versus cancer prevention. In the ECLIPSE study, Shield detected about 83% of colorectal cancers, but only about 65% of stage I cancers and about 13% of advanced precancerous polyps, the lesions colonoscopy removes before they can become cancer. A blood test cannot remove tissue, and a negative result does not rule out polyps.

Any positive blood test still needs a colonoscopy. For now, cfDNA blood tests do not replace colonoscopy or stool tests as preferred screening options; they are a fallback for people who would otherwise not be screened.

Frequently asked questions

Sources

1. USPSTF — Colorectal cancer screening
2. National Cancer Institute — Colorectal cancer
3. MedlinePlus — Colorectal cancer
4. NIDDK — Colonoscopy
5. American College of Gastroenterology — Colorectal cancer
6. American Cancer Society — Guideline for colorectal cancer screening
7. American College of Gastroenterology — Statement on blood-based screening tests (June 2026)
8. Medicare.gov — Colonoscopies
9. Wolf AMD, et al. Colorectal cancer screening: an update to the American Cancer Society guideline, 2026. CA Cancer J Clin. 2026
10. Lin JS, et al. Screening for colorectal cancer: an evidence update for the U.S. Preventive Services Task Force. AHRQ Evidence Synthesis No. 202, 2021 (published in JAMA. 2021;325(19):1978–1998)
11. Imperiale TF, et al. Multitarget stool DNA testing for colorectal-cancer screening (DeeP-C). N Engl J Med. 2014;370:1287–1297
12. Imperiale TF, et al. Next-generation multitarget stool DNA test for colorectal cancer screening (BLUE-C). N Engl J Med. 2024;390:984–993
13. Chung DC, et al. A cell-free DNA blood-based test for colorectal cancer screening (ECLIPSE). N Engl J Med. 2024;390:973–983
14. U.S. Departments of Labor, HHS and Treasury. FAQs about Affordable Care Act Implementation Part 51 (January 10, 2022)

Where to be seen in Katy and Cypress

United Gastroenterology Associates has two offices: Katy, at 23920 Katy Freeway, Suite 555, next to Memorial Hermann Katy Hospital, and Cypress, at 21216 Northwest Freeway, Suite 640, on US-290. Both are open Monday through Friday, 8:30 AM to 5:00 PM, closed for lunch from 12:00 to 1:30 PM, and serve patients from Fulshear, Richmond and across Greater Houston. Call (346) 340-4414 for either office.

If you have severe pain, vomit blood, pass black stools or have chest pain, call 911 or go to the nearest emergency room.