All ICD10 Codes
MS-DRG 866Medical

Viral Illness without MCC

Major Diagnostic Category 18·Grouped by diagnosis·FY 2027

MS-DRG 866 is a Medical Medicare Severity Diagnosis Related Group under Major Diagnostic Category 18 (MDC 18) without a significant Complication or Comorbidity. It maps to 141 ICD-10-CM diagnosis codes. For FY 2027 it carries a relative weight of 0.8692 with a geometric mean length of stay of 2.7 days and an arithmetic mean of 3.5 days. Hospitals use this grouping to determine reimbursement for inpatient stays under Medicare.

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FY 2027 payment data

From Table 5 of the FY 2027 IPPS Final Rule (CMS).

Relative weight:
0.8692 (payment multiplier vs. the average case (1.0))
Geometric mean stay:
2.7 days (used for transfer payments)
Average stay:
3.5 days (arithmetic mean)
Post-acute transfer policy:
No (not subject to it)

Same condition, other severity levels

CMS splits one condition into separate DRGs by how sick the patient is. With MCC pays more than with CC, which pays more than without CC/MCC.

DRGTitleRelative weightMean stay
865Viral Illness with MCC1.34853.7 days
866Viral Illness without MCC (this page)0.86922.7 days

Diagnosis codes (141)

As the principal diagnosis, these ICD-10-CM codes can group to DRG 866. 100% of the codes listed are billable.