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ICD-10-CM R65.21: Severe sepsis with septic shock

R65.21 is the billable ICD-10-CM code for severe sepsis with septic shock, in category R65 (Symptoms and signs specifically associated with systemic inflammation and infection) of the General symptoms and signs section. As a principal diagnosis it groups to MS-DRG 870 Septicemia or Severe Sepsis with MV >96 Hours, MS-DRG 871 Septicemia or Severe Sepsis without MV >96 Hours with MCC, MS-DRG 872 Septicemia or Severe Sepsis without MV >96 Hours without MCC (MDC 18 MDC 18: Infectious and Parasitic Diseases, Systemic or Unspecified Sites). It maps to HCC 2 (Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock) in CMS-HCC V28. As a secondary diagnosis it is an MCC, excluded with 48 principal diagnoses. 20 LCD billing and coding articles list it as covered.

Compiled from CMS files by the QuickIntell RCM Editorial Team · Data effective · Method: reference methodology · Report a data correction

Data currency: ICD-10-CM code descriptions: FY2027 (effective October 1, 2026); IPPS Table 5 (MS-DRG weights): v44 FY2027 (final rule + CN3) (effective October 1, 2026); ICD-10-CM to HCC mapping: PY2027 initial ICD-10-CM mappings (dates of service 2026) (payment year 2027); Medicare Coverage Database billing and coding articles: MCD release October 8, 2026 (effective October 4, 2026). Next CMS release: FY2028 code files, effective October 1, 2027 for the ICD-10-CM code descriptions; FY2028 final rule (August 2027), effective October 1, 2027; an April 1 interim grouper update when CMS issues one for the IPPS Table 5 (MS-DRG weights); PY2028 advance notice (February 2027) and the PY2027 midyear final mapping (spring 2027) for the ICD-10-CM to HCC mapping; weekly, every Thursday for the Medicare Coverage Database billing and coding articles.

Code
R65.21
billable FY2027 ICD-10-CM code
Category
R65 Symptoms and signs specifically associated with systemic inflammation and infection
Chapter
18: Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99)
CC/MCC (MS-DRG v44)
MCC
CMS-HCC V28
HCC 2
POA reporting
Required

Tabular list notes for R65.21

Excludes1 (never coded together)
  • postprocedural septic shock (T81.12-)

Inherited from R65.2 (Severe sepsis)

Inclusion terms
  • Infection with associated acute organ dysfunction
  • Sepsis with acute organ dysfunction
  • Sepsis with multiple organ dysfunction
  • Systemic inflammatory response syndrome due to infectious process with acute organ dysfunction
Code first
  • underlying infection, such as:
  • infection following a procedure (T81.4-)
  • infections following infusion, transfusion and therapeutic injection (T80.2-)
  • puerperal sepsis (O85)
  • sepsis following complete or unspecified spontaneous abortion (O03.87)
  • sepsis following ectopic and molar pregnancy (O08.82)
  • sepsis following incomplete spontaneous abortion (O03.37)
  • sepsis following (induced) termination of pregnancy (O04.87)
  • sepsis NOS (A41.9)
Use additional code
  • code to identify specific acute organ dysfunction, such as:
  • acute kidney failure (N17.-)
  • acute respiratory failure (J96.0-)
  • critical illness myopathy (G72.81)
  • critical illness polyneuropathy (G62.81)
  • disseminated intravascular coagulopathy [DIC] (D65)
  • encephalopathy (metabolic) (septic) (G93.41)
  • hepatic failure (K72.0-)

MS-DRG grouping when R65.21 is the principal diagnosis

MS-DRG v44 groups for R65.21 as principal diagnosis
MDCMS-DRGs
18 MDC 18: Infectious and Parasitic Diseases, Systemic or Unspecified Sites870871872

The final group also depends on procedures, secondary diagnoses and discharge status; the MS-DRG lookup for R65.21 shows the full grouping logic.

CC/MCC status and inpatient edits

As a secondary diagnosis, R65.21 is an MCC under MS-DRG v44, unless the principal diagnosis is one of the 48 codes in its exclusion list. Check R65.21 against a principal diagnosis.

  • Present on admission: a POA indicator is required on inpatient claims.
  • Medicare Code Editor: unacceptable principal diagnosis.

CMS-HCC V28 risk adjustment

In the PY2027 mapping, R65.21 maps to HCC 2 (Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock). The HCC lookup shows the RAF weight and the hierarchy.

LCD billing and coding articles that list R65.21

20 current Medicare billing and coding articles list R65.21 among the diagnoses that support medical necessity for the services they cover.

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Frequently asked questions

What does ICD-10-CM R65.21 mean?

R65.21 means severe sepsis with septic shock. It is one of 4 billable codes under R65, symptoms and signs specifically associated with systemic inflammation and infection.

What can't be coded with R65.21?

Excludes1 at R65.21: postprocedural septic shock (T81.12-). These are never reported together with R65.21.

Which MS-DRG does R65.21 group to?

As the principal diagnosis, R65.21 groups to MS-DRG 870 Septicemia or Severe Sepsis with MV >96 Hours, MS-DRG 871 Septicemia or Severe Sepsis without MV >96 Hours with MCC, MS-DRG 872 Septicemia or Severe Sepsis without MV >96 Hours without MCC (MDC 18 MDC 18: Infectious and Parasitic Diseases, Systemic or Unspecified Sites) under MS-DRG v44, before procedures and secondary diagnoses are applied.

Does R65.21 map to an HCC?

Yes: HCC 2, Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock, in the PY2027 CMS-HCC V28 mapping.

Is R65.21 a CC or MCC?

R65.21 is an MCC under MS-DRG v44; 48 principal diagnoses exclude it.

Sources

Every figure on this page is taken from the CMS publications below, as released by the Centers for Medicare & Medicaid Services. Projection built 2026-10-10. Verify against the primary file before billing or contracting decisions. The reference methodology explains how each figure is computed from these files.

Disclaimer

The descriptor and notes are reproduced from the FY2027 ICD-10-CM files; MS-DRG, CC/MCC and HCC facts come from the CMS FY2027 and PY2027 tables. Code from the medical record and the ICD-10-CM Official Guidelines. Not legal, clinical or billing advice.

Found a figure that does not match the CMS file? Report a data correction with the CMS file and the value you expected; the request reaches the editorial team through the contact form.