Medical coding intensity has become a growing topic of concern in U.S. healthcare as coding-driven impacts on provider reimbursement continue to rise and AI-assisted clinical documentation integrity technologies become increasingly prevalent. The Medicare program alone accounted for approximately 62 million beneficiaries aged 65 and older and $1.2 trillion in total expenditures in 2025, so even modest shifts in coding patterns can translate into millions of dollars in aggregate reimbursement impacts that directly affect program costs, risk adjustment, and the sustainability of payment models. Tracking and interpreting changes in coding behavior has become an important part of assessing provider payment levels, understanding the specific impacts of coding technologies, and making decisions about the long-term approach of payment systems. The implications of coding intensity trends extend across a broad range of stakeholders.
Using Medicare fee-for-service (FFS) claims data from the Virtual Research Data Center, under the Centers for Medicare and Medicaid Services, this paper analyzes nationwide medical coding trends and their associated financial implications. The data includes claims incurred from 2017 through March 2026 and paid through June 2026, the scale and consistency of which make it well-suited for longitudinal trend analysis. While Medicare FFS differs from Medicare Advantage, Medicaid, and commercial markets, the observed coding trends can provide meaningful insight across all lines of business, since nearly all acute-care hospitals participate in Medicare FFS and most physicians accept Medicare patients.
Key discussion points include the following.
- Definitions: Medical coding, coding intensity, and upcoding.
- Coding intensity in emergency department care and its impact: Visit distribution by Current Procedural Terminology (CPT) code and average Ambulatory Payment Classifications weight per visit, 2017 to 2026, plus other statistics.
- Coding intensity in inpatient care and its impact: Share of inpatient admissions with a Complications or Comorbidities (CCs) or Major Complications or Comorbidities (MCCs) secondary diagnosis across 16 Clinical Classifications Software Refined body systems, among other examples.