ICD-10 Code F99: Mental disorder, not otherwise specified
F99 is a billable ICD-10 diagnosis code used to classify Mental disorder, not otherwise specified in medical records and claims. You may see this code in hospital records, discharge summaries, insurance claims, encounter documentation, referrals, or other healthcare billing and coding records. ICD-10 codes are diagnosis classification codes used in healthcare records, reporting, coding workflows, and billing support. This code sits within the broader ICD-10 area for Mental, Behavioral and Neurodevelopmental disorders (F01-F99).
What is this code?
ICD-10 codes are diagnosis classification codes used in healthcare records, reporting, coding workflows, and billing support. This code sits within the broader ICD-10 area for Mental, Behavioral and Neurodevelopmental disorders (F01-F99).
When is it used?
- May be used when a clinician documents mental disorder, not otherwise specified in a patient's medical record.
- May appear in hospital records, claims, referrals, and clinical documentation.
- This code can be used as a clinically usable diagnosis entry in standardized coding workflows.
What it does not mean
- A code alone does not explain severity, treatment plan, or outcome.
- A medical code should not be treated as a substitute for a doctor's diagnosis or advice.
Code hierarchy
Official coding notes
- Mental illness NOS
- unspecified mental disorder due to known physiological condition (F09)
Where you may see this code
You may see this code in hospital records, discharge summaries, insurance claims, encounter documentation, referrals, or other healthcare billing and coding records.
Related specialists
Related codes
Coverage-related procedures and services
Mapped diagnoses and classifications
Coding guidelines
Compatibility
Common synonyms
Frequently asked questions
About this content
This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.