F99
Mental disorder, not otherwise specified
F99 is a billable ICD-10-CM diagnosis code for mental disorder, not otherwise specified. It is part of the FY2027 code set, effective October 1, 2026. The Alphabetic Index lists it under 10 entries. Its coding notes include 1 Excludes1 entry and 1 Excludes2 entry.
Excludes1
Not coded here. The listed conditions generally should not be reported together.
- unspecified mental disorder due to known physiological condition (F09)
Excludes2
Not included here. Both codes may be reported if the patient has both conditions.
Also from chapter/block level (1 note)
- symptoms, signs and abnormal clinical laboratory findings, not elsewhere classified (R00-R99)
Care settings
How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.
IPF Primary
IPF MS-DRG adjustment. A principal diagnosis of this code groups to this MS-DRG:
| MS-DRG | Description | Factor |
|---|---|---|
| 880 | Acute adjustment reaction & psychosocial dysfunction | 1.08 |
Includes
Further defines or gives examples of the content of the category.
Also from chapter/block level (1 note)
- disorders of psychological development
Inclusion terms
Conditions classified to this code.
- Mental illness NOS
Alphabetic Index terms
Terms the official Alphabetic Index lists for this code. 10 entries