Ill-defined and unknown cause of mortality (R99) ICD-10-CM
The R99 code range covers ill-defined and unknown cause of mortality with 1 ICD-10-CM diagnosis codes. 1 of them are billable and valid for claim submission in fiscal year 2027, and the category headers group them but cannot themselves be billed.
Inclusion Terms
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
- Death (unexplained) NOS
- Unspecified cause of mortality
Codes in the R99 Range 1 codes · 1 billable
- R99 Ill-defined and unknown cause of mortality
Clinical Terms in This Code Range
Definitions from the National Library of Medicine for conditions coded in the R99 range.
Death
Irreversible cessation of all bodily functions, manifested by absence of spontaneous breathing and total loss of cardiovascular and cerebral functions.
Sudden Infant Death
The abrupt and unexplained death of an apparently healthy infant under one year of age, remaining unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of the clinical history. (Pediatr Pathol 1991 Sep-Oct;11(5):677-84)
About the R99 Code Range
When the cause of death is unclear or unknown, it falls under R99. Death means the irreversible end of bodily functions, with no spontaneous breathing or cardiovascular or brain function.
Questions About This Page
How many billable codes are in the R99 range?
Of the 1 codes in this range, 1 are billable and valid for claim submission from October 1, 2026 through September 30, 2027. Category header codes group them but cannot be reported on claims.
What does the R99 range classify?
The range classifies ill-defined and unknown cause of mortality. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2027 ICD-10-CM Tabular List and order file, effective October 1, 2026 through September 30, 2027.
