Medical Necessity
The requirement that a billed service be appropriate and necessary for the patient's diagnosis, per payer rules.
When the diagnosis (ICD-10) doesn't support the procedure (CPT), payers deny for lack of medical necessity. Catching these mismatches before submission - rather than after a denial - is a major lever on first-pass rates.
Payer medical-necessity policies (LCDs/NCDs) define what's covered.