MS-DRG: Medicare Severity-Adjusted Diagnosis Related Group
MS-DRGs are CMS's hospital inpatient payment classification system. Each Medicare inpatient stay groups into one of ~770 MS-DRGs, which carries a relative weight that drives the payment formula and the geometric mean length of stay benchmark.
What is an MS-DRG?
Medicare Severity-Adjusted Diagnosis Related Groups (MS-DRGs) replaced the original DRG system in FY 2008. Every Medicare fee-for-service inpatient discharge is assigned one MS-DRG based on principal diagnosis, secondary diagnoses, procedures performed, sex, and discharge status. Each MS-DRG carries a CMS-published relative weight that, combined with the hospital's base operating rate, sets the payment for that stay.
How severity stratification works
Most clinical conditions split into three MS-DRGs by severity:
- MCC — with Major Complication or Comorbidity (highest weight)
- CC — with Complication or Comorbidity (middle)
- Without CC/MCC — base case (lowest weight)
Documentation of secondary diagnoses determines which severity tier a discharge groups to. A heart failure admission documented without the CHF subtype, BNP elevation, or volume status notes can group to the lowest tier when clinically the patient warranted MCC. The financial gap is meaningful — commonly $5K-15K per discharge.
MS-DRG analytics that hospitals run
- CMI trend — Case Mix Index by service line; rising CMI generally signals stronger documentation or higher acuity.
- LOS vs geometric mean — by MS-DRG; outlier service lines surface operational opportunities.
- Documentation opportunity — discharges grouped to base or CC where MCC was clinically supported.
- HRRP overlap — readmission rates by MS-DRG to surface penalty-risk cohorts.
Where Vizier fits
Vizier reads the full inpatient encounter dataset from your EHR (Epic, Cerner / Oracle Health, MEDITECH, etc.) including all coded diagnoses, procedures, and discharge dispositions. The MS-DRG dashboards surface CMI trend, documentation opportunity by clinical service line, and the financial impact of moving documentation from base to CC or CC to MCC where clinically supported.