Yes. Medicare Part B covers stool tests, both as preventive screenings and as diagnostic lab work, and in most cases you pay nothing out of pocket when your provider accepts assignment. Stool tests are clinical laboratory tests, and Medicare covers clinical lab work at no cost to the beneficiary. Costs usually appear later, if a positive result leads to a follow-up procedure such as a colonoscopy.
Screening Stool Tests Covered by Part B
Medicare covers three stool-based screenings for colorectal cancer, each on its own schedule, and all with no deductible and no coinsurance when the provider accepts assignment.1Medicare.gov. Fecal Occult Blood Tests
- Fecal occult blood test (FOBT) or fecal immunochemical test (FIT): once every 12 months for beneficiaries 45 or older. These tests look for hidden blood in the stool.1Medicare.gov. Fecal Occult Blood Tests
- Multi-target stool DNA test (the brand-name version is Cologuard): once every three years for beneficiaries 45 to 85 who have no symptoms and are at average risk. It checks stool for both blood and DNA markers linked to colorectal cancer.2Centers for Medicare & Medicaid Services. National Coverage Determination 210.3 – Colorectal Cancer Screening Tests
- Blood-based biomarker test: once every three years. Approved tests in this category remain limited.3Medicare.gov. Blood-Based Biomarker Tests
Who Qualifies for a Screening Stool Test
The annual FOBT or FIT has one requirement: you’re 45 or older and enrolled in Part B. No medical history rules apply.1Medicare.gov. Fecal Occult Blood Tests
The stool DNA test is stricter. You must be 45 to 85, symptom-free, and at average risk. CMS defines average risk by what you don’t have: no personal history of adenomatous polyps, colorectal cancer, or inflammatory bowel disease (including Crohn’s disease and ulcerative colitis), and no family history of colorectal cancer, adenomatous polyps, familial adenomatous polyposis, or hereditary nonpolyposis colorectal cancer.2Centers for Medicare & Medicaid Services. National Coverage Determination 210.3 – Colorectal Cancer Screening Tests
If any of those risk factors apply to you, the stool DNA test isn’t covered under the screening benefit. Your doctor can still order the annual FIT, or move you to a screening colonoscopy on a shorter cycle based on your history.
What You Pay for a Diagnostic Stool Test
A diagnostic stool test is one your doctor orders because you already have symptoms, such as persistent diarrhea, abdominal pain, or blood in your stool. A stool test ordered as follow-up to an earlier positive screening also counts as diagnostic. Doctors also use diagnostic stool tests to check for parasites, bacteria, or signs of inflammatory bowel disease.
Diagnostic stool tests are clinical laboratory tests, and Medicare covers clinical diagnostic lab work with no cost-sharing when the provider accepts assignment. You typically pay nothing for a diagnostic stool test, the same as for a screening stool test.4Medicare.gov. Clinical Laboratory Tests
The standard Part B structure of a $283 deductible in 2026 followed by 20% coinsurance applies to many services, but clinical laboratory tests are an exception.5Centers for Medicare & Medicaid Services. 2026 Medicare Parts A and B Premiums and Deductibles That standard cost-sharing does apply to diagnostic non-laboratory tests. After you meet the $283 deductible, you pay 20% of the Medicare-approved amount for covered diagnostic procedures done in a doctor’s office or an independent testing facility.6Medicare.gov. Diagnostic Non-Laboratory Tests
The Real Cost Comes From the Follow-Up Colonoscopy
A positive stool screening test almost always leads to a colonoscopy, and this is where most people are caught off guard by a bill.
If the colonoscopy is purely diagnostic and nothing is found or removed, you pay nothing. Medicare treats it as part of the screening process, with no deductible and no coinsurance, provided the doctor accepts assignment.7Medicare.gov. Colonoscopies – Screening
If the doctor finds and removes a polyp or takes tissue during the procedure, the colonoscopy becomes therapeutic. In 2026 you owe 15% coinsurance on the Medicare-approved amount, with no Part B deductible. Congress is phasing that share down to zero:7Medicare.gov. Colonoscopies – Screening
- 2023 through 2026: 15% coinsurance, no deductible
- 2027 through 2029: 10% coinsurance, no deductible
- 2030 and later: no coinsurance, no deductible
Even at 15%, a colonoscopy with polyp removal in a hospital outpatient setting can leave you with a meaningful bill.
How Medigap and Medicare Advantage Change the Numbers
Medicare Advantage plans have to cover everything Original Medicare covers, screening and diagnostic stool tests included. Preventive screenings stay at $0. For diagnostic procedures beyond lab work, your plan sets its own copays and coinsurance and may require in-network providers. Your plan’s Evidence of Coverage has the specifics.8Medicare.gov. Understanding Medicare Advantage Plans
With Original Medicare plus a Medigap policy, the supplement can pick up remaining Part B cost-sharing. On a follow-up colonoscopy where a polyp is removed and you owe 15% coinsurance, a Medigap plan that covers Part B coinsurance would pay that share. Most standardized Medigap plans pay 100% of Part B coinsurance; Plan K and Plan L cover a partial share.9Medicare. Compare Medigap Plan Benefits