Can a Blood Test Replace Colonoscopy? What ACS Changed in 2026

Short answer: no. A blood test can now be one option for colorectal cancer screening, but it does not replace colonoscopy for most people.

On May 27, 2026, the American Cancer Society updated its colorectal cancer screening guideline for average-risk adults. The practical change is that blood-based screening joined the list of recommended options. But the group also made an equally important point: visual exams such as colonoscopy and stool-based tests are still the preferred choices, and any positive non-colonoscopy test still needs a timely follow-up colonoscopy.

What changed in the 2026 ACS update

The updated guideline keeps the same basic starting point for most average-risk adults: begin regular colorectal cancer screening at age 45. The American Cancer Society says screening should usually continue through age 75 for people with a life expectancy greater than 10 years. From ages 76 through 85, the decision should be individualized. After age 85, screening generally should stop.

The new part in 2026 is that blood-based screening and newer stool-based options were added to the menu. That does not mean every option is equally strong. The guideline says blood-based tests are not a preferred option right now because research shows they are less likely to find precancerous growths and very early cancers than established stool-based tests and visual exams.

That distinction matters. A test being included in a guideline is not the same as that test becoming the best first choice for everyone.

What the blood-based screening option does — and does not do

The FDA-cleared test most readers will hear about here is Shield, a blood-based biomarker test meant for adults age 45 and older who are at average risk and need colorectal cancer screening.

What it can do: offer a lower-barrier screening option for some people who might otherwise avoid screening altogether.

What it cannot do: replace colonoscopy when someone needs a diagnostic workup, surveillance because of higher risk, or follow-up after an abnormal result. The FDA says people with positive results are advised to have a diagnostic colonoscopy, and a negative result does not guarantee that a person does not have colorectal cancer.

The performance details help explain why ACS stopped short of treating blood testing as equal to colonoscopy. In the FDA-reviewed study of 7,861 people, Shield detected colorectal cancer 83% of the time, and about 1 in 10 people who did not have advanced abnormal cells had a false-positive result. That is useful, but it is not the same as a test that can directly look inside the colon and remove polyps.

Why colonoscopy is still preferred for many people

For many patients, colonoscopy remains the more complete test. It is not just a cancer-detection tool. It is also a prevention tool, because doctors can remove polyps during the procedure.

That prevention angle is a major reason blood testing has not replaced colonoscopy. The American Cancer Society says blood-based tests are less likely to find precancerous growths and stage I cancer. In plain language, they are better viewed as an additional option than as a direct substitute for the most established screening methods.

That said, the best screening test is still the one a person will actually complete. If someone keeps putting off screening because bowel prep, time off, transportation, or stool testing feels like too much, a blood-based option may be better than no screening at all. That patient-choice point is part of the updated guideline and part of why the option was added.

Who the blood option is meant for

This option is aimed at average-risk adults. That usually means people without symptoms and without a personal history, family history, or medical condition that raises colorectal cancer risk.

People may need a different plan if they have a history of colorectal cancer or adenomas, a strong family history, a hereditary cancer syndrome such as Lynch syndrome, inflammatory bowel disease, prior abdominal or pelvic radiation, or another reason they are considered higher risk. The FDA also says Shield should not be used for people under 45 or for people who had a positive result from another colorectal cancer screening method within the previous 6 months.

If you already know you are in a higher-risk category, this is not a decision to make on your own based on convenience. Talk with your clinician about the screening plan that matches your risk.

If your blood or stool screening test is positive, the next step is a colonoscopy

This is the part readers should remember most clearly: a positive blood or stool screening test does not finish the process. It starts the next step.

The American Cancer Society says all positive results on non-colonoscopy screening tests should be followed by a timely colonoscopy. Medicare says that if you first get a Medicare-covered stool-based or blood-based colorectal cancer screening test and it is positive, Part B also covers a follow-up colonoscopy as a screening test.

If that follow-up does not happen, the screening process is incomplete. That is one reason clinicians are careful about recommending blood testing to the right patients and explaining the next steps ahead of time.

Coverage basics: what Medicare says, and what to ask private insurers

Medicare Part B covers screening colonoscopies, with timing rules that depend on risk level and prior testing. Medicare also says that if your provider accepts assignment, you pay nothing for the screening test, including covered follow-up colonoscopies after a positive Medicare-covered blood-based or stool-based screening test. If a polyp or other tissue is removed during the colonoscopy, other costs can still apply.

Private-plan coverage can be less straightforward. Before you choose a blood-based option, ask your insurer:

Is this specific colorectal blood screening test covered under my plan?
Do I need prior authorization?
Is the lab in network?
If the test is positive, how will the follow-up colonoscopy be billed?
What costs apply if a polyp or tissue is removed during that colonoscopy?

Those questions can help you avoid surprise bills.

What readers can do now

If you are 45 to 75 and at average risk, this update is a good reason to check whether you are up to date on screening. If you are not, ask which test is realistic for you and which one best fits your risk, schedule, and access to care.

If you are older than 75, or if you have a history that puts you at higher risk, ask for a more individualized discussion instead of assuming the new blood option applies to you.

And remember: screening is for people without symptoms. If you have rectal bleeding, black stools, unexplained weight loss, a lasting change in bowel habits, or ongoing abdominal pain, contact a clinician promptly because you may need medical evaluation rather than routine screening. Severe bleeding, fainting, or severe abdominal pain needs urgent care.

Questions to bring to your next visit

Am I average risk or higher risk for colorectal cancer?
Would a stool-based test, blood-based test, or colonoscopy make the most sense for me?
If I choose a blood test and it is positive, how quickly would I need a colonoscopy?
What are the likely out-of-pocket costs with my insurance?
If I am not up to date on screening, what is the safest next step and by when?

The bottom line is simple: the 2026 guideline update gives average-risk adults another screening option, not a colonoscopy replacement. For many people, especially those willing and able to use a stool-based test or get a colonoscopy, the older options still offer stronger prevention value. But for people who might otherwise skip screening, a blood test may be a practical way to get started.

Sources

Editorial note: Weence articles are researched from cited public-health, medical, regulatory, journal, and reputable news sources and may be drafted with AI assistance. They are checked for source support, clarity, and safety guardrails before publication.

This article is for general informational purposes only and is not medical advice. Research findings can be early or incomplete, and health guidance can change. Always talk with a qualified healthcare professional about personal symptoms, diagnosis, medications, vaccines, screenings, or treatment decisions. If you think you may have a medical emergency, call emergency services right away.