ICD-10-CM · Chapter 5 · F01-F99
F99 Mental disorder, not otherwise specified
Includes
- Mental illness NOS
Excludes 1 (cannot be coded together)
- unspecified mental disorder due to known physiological condition (F09)
This category is a complete, billable diagnosis code.
No additional specificity is required — submit F99 directly on claims and documentation without a subcode extension.
Last reviewed: September 2026