R99
Billable codeIll-defined and unknown cause of mortality
The ICD-10 code for ill-defined and unknown cause of mortality is R99.
Clinical notes
Also known as
Alternate wording, synonyms, or specific conditions that fall under this code, listed to help confirm you've picked the right one.
- Death (unexplained) NOS
- Unspecified cause of mortality
Documentation support
General coding-documentation guidance — not a substitute for payer-specific requirements or professional coding judgment.
- •As a general rule, code to the highest level of specificity supported by the documentation in the medical record.
ICD-9-CM equivalent
Informational only — GEM mappings are approximate, not guaranteed one-to-one equivalents. Verify before use in billing.
- 7980Approximate match
- 7999Approximate match
- 7981Approximate match
- 7982Approximate match
- 7989Approximate match
Associated MS-DRGs
R99 can serve as the principal diagnosis for these Medicare Severity Diagnosis-Related Groups.
Informational only — actual DRG assignment also depends on procedures, complications/comorbidities (CC/MCC), discharge status, and payer-specific rules not reflected here.