Billable / Specific Code
ICD-10-CM R99 is the diagnosis code for Ill-defined and unknown cause of mortality. This code falls under the section "Ill-defined and unknown cause of mortality" within Chapter 18 — Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99). It is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes. Medical coders and healthcare providers use this code to document and classify diagnoses in electronic health records, insurance claims, and clinical databases.
Understanding where R99 sits in the ICD-10-CM classification helps ensure proper coding:
Yes, R99 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.
R99 is the ICD-10-CM diagnosis code for "Ill-defined and unknown cause of mortality". It is used by healthcare providers to classify and document this condition in medical records and insurance claims.
R99 is located in Section R99 — "Ill-defined and unknown cause of mortality" within Chapter 18 of the ICD-10-CM Tabular List.
Use R99 when the patients documented diagnosis matches "Ill-defined and unknown cause of mortality" and the clinical documentation supports this level of specificity. Always verify with the latest ICD-10-CM guidelines and payer requirements.
The ICD-10-CM code for Ill-defined and unknown cause of mortality is R99.
Yes, R99 can be used as a primary diagnosis code since it is billable and specific.
R99 is in Chapter 18 of the ICD-10-CM Tabular List.
Yes, R99 is a valid ICD-10-CM code for the 2026 fiscal year, subject to official CMS updates.