Medicare Denied Lab Work or Diagnostic Test

What This Means

Your Medicare Summary Notice or Explanation of Benefits shows the test denied under a coverage rule — usually CARC CO-50, “these are non-covered services because this is not deemed a ‘medical necessity’ by the payer,” or CO-167, “this (these) diagnosis(es) is (are) not covered” — which usually means the diagnosis code sent with the test was not on Medicare’s approved list for it. If no one asked you to sign an Advance Beneficiary Notice before the test — the form warning that Medicare probably would not pay — the lab generally cannot bill you for it. That protection covers tests denied as not medically necessary, which is what these codes mean; it does not cover a test Medicare never pays for under any diagnosis, where you owe the bill whether or not anyone handed you a notice. Either way, start here: call the office of the doctor who ordered the test and ask them to check the diagnosis code, then send any correction to the lab — the lab is the one that billed Medicare and has to resubmit, but it can only use the code the ordering doctor supplies. A corrected code resolves many of these without an appeal.

Those approved lists are Medicare’s National and Local Coverage Determinations, and you can look your own test up in the CMS Medicare Coverage Database. If you did sign an ABN, or the corrected claim comes back denied, the standard clock governs: 120 days from the date you receive your Medicare Summary Notice for Original Medicare — receipt is presumed 5 days after the date printed on it, and the MSN states your exact deadline — or 65 days from the date on your denial notice for Medicare Advantage (appeals).

Not sure this is your situation? “Lab test denied” catches searches that belong on a neighboring guide:

• Was the denied service not a lab or diagnostic test — an office visit, a procedure, or therapy turned down as not medically necessary? See not medically necessary.
• Does your notice say your diagnosis itself isn’t covered for the service, whatever the service was? See diagnosis not covered.
• Was it a screening you expected to be free — a cholesterol, diabetes, or cancer screening? See preventive service denied.

This doesn’t necessarily mean the test wasn’t needed. It may mean the paperwork didn’t support coverage under Medicare’s specific rules.

Why This Happens

• The diagnosis code didn’t match the test. Medicare maintains detailed lists of which diagnosis codes justify each lab test. These lists are called National Coverage Determinations (NCDs) and Local Coverage Determinations (LCDs). If the code on your claim isn’t on the approved list for that test, Medicare denies it automatically.
• The test exceeded a frequency limit. Medicare limits how often certain tests can be performed. For example, some blood tests are covered once per year or once every two years. If your test was ordered sooner than the allowed interval, it may be denied.
• The test was considered screening, not diagnostic. Medicare draws a line between “screening” tests (checking for a disease when you have no symptoms) and “diagnostic” tests (investigating a specific symptom or condition). Some screening tests are only covered on a set schedule or not at all.
• Missing or incomplete documentation. The lab or your doctor’s office may not have submitted enough information to support medical necessity.
• The test isn’t covered by Medicare. Some newer or specialized tests may not yet have a coverage determination, or Medicare may have specifically decided not to cover them.

Should You Appeal?

What To Do Next

1. Check whether you signed an ABN. If your provider gave you an Advance Beneficiary Notice before the test and you signed it, you may be financially responsible. If you did not receive an ABN, the lab generally cannot bill you for a test denied as not medically necessary — though that protection does not extend to tests Medicare never covers under any diagnosis.
2. Contact your doctor’s office first. Ask them to review the diagnosis code on the claim. If a more specific or accurate code applies, they supply it to the lab, which resubmits the claim — the lab cannot choose a code on its own. This route is usually faster than a formal appeal.
3. Review your denial notice. Your Medicare Summary Notice (MSN) or Explanation of Benefits (EOB) will indicate the reason for the denial. Look for references to medical necessity, coverage criteria, or frequency limits.
4. If resubmission doesn’t work, file an appeal. Ask your doctor for a letter explaining why the test was medically necessary for your condition. Include this with your appeal along with any relevant medical records.
5. Check the LCD or NCD for your test. You can look up coverage rules in the CMS Medicare Coverage Database. This can help you understand what Medicare requires and whether your situation qualifies.
6. Get free help. Contact your State Health Insurance Assistance Program (SHIP) or call 1-800-MEDICARE (1-800-633-4227).

Sources

• Medicare.gov: Diagnostic Laboratory Tests
• CMS: Medicare Coverage Database — NCDs and LCDs
• CMS: Medicare Coverage Determination Process
• CMS: Local Coverage Determinations

Frequently Asked Questions