Yes, Medicare Part B covers clinical laboratory services, including blood tests, urinalysis, and other diagnostic tests ordered by your doctor. The critical distinction: preventive screening lab tests cost you nothing, while diagnostic lab tests (ordered due to symptoms or conditions) cost 20% coinsurance after your deductible. Knowing which category applies before your blood draw prevents surprise bills.
Laboratory tests are among the most frequently billed Medicare Part B services — hundreds of millions of lab claims are processed annually. For most Medicare beneficiaries, lab work is a routine part of care for chronic conditions, annual monitoring, and preventive screenings. Here’s exactly how the coverage works.
Article Contents
The Core Rule: Preventive vs. Diagnostic
Everything about Medicare lab cost-sharing hinges on this distinction:
Preventive screening labs = $0 to you. Lab tests ordered as part of Medicare’s covered preventive screenings—on the defined schedule—have no deductible and no coinsurance. You pay nothing.
Diagnostic labs = 20% coinsurance after your Part B deductible. When a lab test is ordered because you have symptoms, a known condition, or your doctor is monitoring an existing problem, it is classified as diagnostic. Medicare covers 80%; you pay 20% after your annual $283 deductible.
The same test can be billed either way depending on the reason it was ordered. A lipid panel ordered at your annual wellness visit as routine screening is preventive and free. A lipid panel ordered three months later because your cholesterol was high and your doctor is monitoring your response to statins is diagnostic and costs you 20%.
Preventive Lab Tests Medicare Covers at 100% (No Cost to You)
| Lab Test / Screening | Coverage Frequency | Your Cost |
|---|---|---|
| Cardiovascular disease risk screening (lipid panel — cholesterol, HDL, LDL, triglycerides) | Once every 5 years | $0 |
| Diabetes screening (fasting glucose or HbA1c) | Up to 2 per year if at risk | $0 |
| Colorectal cancer screening (fecal occult blood test) | Once per year | $0 |
| Stool DNA test / Cologuard | Once every 3 years (ages 45–85) | $0 |
| Cervical and vaginal cancer screening (Pap smear) | Once every 24 months (more often if high risk) | $0 |
| HIV screening | Once per year if at increased risk; once for all beneficiaries aged 15–65 | $0 |
| Hepatitis C screening | Once (for adults born 1945–1965); annually if high risk | $0 |
| Hepatitis B screening | Once per year for high-risk individuals | $0 |
| STI screening and counseling | Up to 2 screenings per year for high-risk individuals | $0 |
| Alcohol misuse screening | Annually | $0 |
| Depression screening | Annually | $0 |
| Lung cancer screening (low-dose CT scan — not a blood test, but a covered preventive screening) | Annually for high-risk smokers aged 50–77 | $0 |
Diagnostic Lab Tests — What You Pay
When your doctor orders lab work to diagnose, treat, or monitor a health condition—rather than as a scheduled preventive screening—the test is billed as a diagnostic laboratory service under Part B. Medicare pays 80%; you pay 20% after your annual $283 deductible is met.
Common diagnostic lab tests covered at 80/20:
| Test | Common Reason Ordered | Medicare Coverage |
|---|---|---|
| Complete Blood Count (CBC) | Infection, anemia, medication monitoring | 80% after deductible |
| Comprehensive Metabolic Panel (CMP) | Kidney/liver function, electrolytes, blood sugar | 80% after deductible |
| Thyroid function (TSH, T3, T4) | Hypothyroidism/hyperthyroidism monitoring | 80% after deductible |
| HbA1c (glycated hemoglobin) | Diabetes monitoring (beyond preventive screening) | 80% after deductible |
| PSA (prostate-specific antigen) | Prostate cancer monitoring; 1/year for men 50+ (preventive) | $0 for annual preventive PSA; 80% if ordered diagnostically |
| Lipid panel (ordered more than 5-year frequency) | Statin monitoring, cardiovascular management | 80% after deductible |
| Prothrombin time / INR | Warfarin/Coumadin monitoring | 80% after deductible |
| Vitamin D level | Bone health, supplementation monitoring | 80% after deductible (if medically indicated) |
| Urinalysis (UA) | Infection screening, kidney monitoring | 80% after deductible |
| Blood culture | Infection diagnosis | 80% after deductible |
| Genetic testing (if clinically indicated) | Hereditary cancer risk, pharmacogenomics | Coverage varies; prior authorization often required |
The Surprise Lab Bill Problem — and How to Avoid It
The most common cause of unexpected Medicare lab bills: Your doctor orders additional tests during what you thought was a preventive annual wellness visit. The wellness visit itself is free — but any tests ordered because of findings at that visit (not as part of the standard preventive protocol) are billed as diagnostic and trigger your deductible and 20% coinsurance.
For example: You go to your Annual Wellness Visit expecting a free preventive appointment. Your doctor notices you seem tired and orders a CBC, thyroid panel, and iron studies to investigate. Those are diagnostic orders — not preventive screenings — and they generate a bill. The visit itself remains free; the lab work does not.
How to avoid surprise lab bills:
- Ask before blood is drawn: “Will these tests be billed as preventive or diagnostic?” A good front desk or nurse can check the order codes.
- Know your Annual Wellness Visit coverage: The AWV covers a specific protocol—health risk assessment, vital signs, advance directive discussion, and referrals for preventive services. Blood work is not included in the AWV itself unless it falls under a separately covered screening (like the once-every-5-years lipid panel).
- Use a Medicare-participating lab: Quest Diagnostics, LabCorp, and most hospital-affiliated labs are Medicare-participating and will bill Medicare directly. Out-of-network labs can charge substantially more.
- Check for Medigap coverage: If you have a Medigap plan that covers the Part B coinsurance (Plan G, Plan N, etc.), your 20% lab coinsurance is covered after your deductible is met—diagnostic lab work costs you nothing at the point of service.
Does Medicare Cover Lab Work at Any Lab?
Medicare Part B covers lab tests at Medicare-participating clinical laboratories, which include most major independent labs (Quest, LabCorp), hospital outpatient labs, and physician office labs that are CLIA-certified. Medicare sets a fixed fee schedule for lab services, labs that participate in Medicare agree to accept this fee and cannot charge you more than the deductible and coinsurance amounts.
You do not need a referral to go to any Medicare-participating lab. Your doctor’s order is sufficient. However, your doctor may have a preferred lab they work with for electronic results integration—ask which lab they typically use, and confirm that lab accepts Medicare.
Frequently Asked Questions
Does Medicare cover genetic testing such as BRCA testing for cancer risk?
Medicare covers certain genetic tests when medically indicated and ordered by a physician. BRCA1/BRCA2 genetic counseling and testing is covered for women meeting clinical criteria for elevated hereditary breast and ovarian cancer risk. Coverage for other genetic tests (pharmacogenomic testing, tumor genomic profiling) is evolving—some are covered with prior authorization, others require appeals. Check with your Medicare administrative contractor for the most current local coverage determination.
Does Medicare cover vitamin B12 testing?
Yes — when medically indicated. B12 deficiency is common in older adults (especially those on metformin) and is covered as diagnostic lab work at 80% after the deductible when ordered by a physician for clinical reasons. Routine vitamin panels ordered without specific medical indication may not be covered.
Does Medicare cover COVID-19 tests?
Medicare covers diagnostic COVID-19 testing when ordered by a healthcare provider at 100% with no cost-sharing. Over-the-counter at-home tests are not covered under traditional Medicare, though some Medicare Advantage plans may include OTC test allowances through their supplemental benefits.
Can I get lab work done without a doctor’s order on Medicare?
Generally no—Medicare requires a physician order for covered lab services. Direct-to-consumer lab testing (such as ordering your own blood panel through services like Any Lab Test Now or Life Extension) is not covered by Medicare and must be paid out of pocket.
Related Medicare Coverage Guides:
Does Medicare Cover Diabetic Supplies? • Does Medicare Cover Colonoscopy? • Does Medicare Cover Annual Physical Exams? • Does Medicare Cover It? Complete Guide
This article is for informational purposes only. Medicare lab test coverage rules are governed by national and local coverage determinations. Whether a specific test is covered—and at what cost-sharing rate—depends on the diagnosis codes your physician uses when ordering the test. Verify at Medicare.gov or ask your physician’s office before your lab visit.
