F99
ICD-10BillableMental disorder, not otherwise specified
Official ICD-10-CM descriptor (FY2026)
Mental disorder, not otherwise specified
F99 is valid for submission on a claim — CMS flags it as a billable, specific code.
Inclusion terms
- Mental illness NOS
Excludes1
Not coded here. An Excludes1 code should never be reported at the same time as the code above it.
- unspecified mental disorder due to known physiological condition (F09)
Where this code sits
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ICD-10-CM FY2026. Centers for Medicare & Medicaid Services (CMS) / National Center for Health Statistics (NCHS), “2026 ICD-10-CM Code Descriptions in Tabular Order” (icd10cm_order_2026.txt). Download the original file from cms.gov. Public domain (US Government work). Descriptors, billable flags and instructional notes on this page are reproduced from that file without modification. Krasyn adds no clinical guidance.