Billing for Lab Tests: P-Code HCPCS Reference

P-codes in HCPCS Level II cover pathology and laboratory services — blood chemistry tests, urinalysis, microbiology, and other diagnostic assays. They sit alongside CPT lab codes (the 80000-89999 range) in the clinical laboratory billing landscape. Independent laboratories that accept Medicare assignment bill under the Clinical Laboratory Fee Schedule, with rates that are separate from the physician fee schedule. Browse P-codes by filtering the code browser to P. Rates appear on the fee schedules page.

The Clinical Laboratory Improvement Amendments (CLIA) program governs what tests a laboratory is certified to perform, and CLIA certification level (waived, moderate complexity, high complexity) determines which codes a facility may bill. Billing a code that requires a higher complexity certification than the lab holds is a compliance violation, even if the test was performed correctly.

Panel codes — both CPT and HCPCS — bundle multiple individual tests into a single code when all components of the panel are performed. Unbundling a panel (billing the individual tests separately when the panel code should be used) is a common audit finding. NCCI edits enforce bundling for many lab code combinations; check the NCCI edit overview when billing multiple lab codes on the same date.

The Clinical Laboratory Fee Schedule is updated annually. Payment rates for lab tests under the Protecting Access to Medicare Act (PAMA) are set based on market price data collected from laboratories. PAMA-based rates have reduced lab payments for many common tests over successive update cycles. Monitor the quarterly updates and annual fee schedule releases for rate changes affecting your test menu.