Medically unlikely edits (MUE)

An MUE is a ceiling on units. CMS defines a medically unlikely edit as the maximum units of service a provider would report for a HCPCS or CPT code for the same beneficiary on the same date of service on the vast majority of appropriately reported claims. Medicare Administrative Contractors apply the values to Part B claims to reduce improper payments. CMS publishes most of the values on its website, but some are confidential and not released, and not every code has one.

The edit shows up on the remittance as a reduced or denied line, often with CARC 151, which X12 describes as a payment adjustment because the payer deems the submitted information does not support this many or this frequency of services. Check how the payer applies the value before assuming that splitting the units across lines with a modifier will help; for many codes it only produces a second denial on the second line.

The mistake is treating every unit denial as an error at the payer. Sometimes the units really were right: bilateral procedures, multiple lesions, timed codes with long sessions. Then the fix is documentation and an appeal, not a corrected claim with fewer units. More often the unit count is a typo, a default quantity or a timed code counted in minutes instead of units, and the fix is a corrected claim and a scrubber rule that checks units against the published MUE table before the claim leaves.