R99 Ill-defined and unknown cause of mortality

Billable ICD-10-CM code, FY2026.

Applicable to

• Death (unexplained) NOS
• Unspecified cause of mortality

Applies from R99 Ill-defined and unknown cause of mortality

Applicable to

• Death (unexplained) NOS
• Unspecified cause of mortality

MS-DRG index

Defines the logic of DRG(s) 951 in MDC 23.

Approximate ICD-9-CM (GEMs)

• 798.0 Sudden infant death syndrome (approximate)
• 799.9 Other unknown and unspecified cause of morbidity and mortality (approximate)

Diagnosis Index entries for R99

• Cot death
• Crib death
• Death (cause unknown) (of) (unexplained) (unspecified cause)
• Sudden infant death syndrome (SIDS)
• Syndrome › crib death

Nearby codes

• R99 Ill-defined and unknown cause of mortality (this code)