ICD-10-CM 2027
ICD-10 code for psychological disorder
From the official ICD-10-CM alphabetic index entry “Disorder (of) › psychological”. Page updated September 29, 2026.
About coding psychological disorder
The ICD-10-CM code for psychological disorder is F99 (Mental disorder, not otherwise specified). The official index lists 4 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on F99.
Don't report F99 together with the conditions in its Excludes1 note: unspecified mental disorder due to known physiological condition (F09).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 880 (Acute Adjustment Reaction and Psychosocial Dysfunction, relative weight 0.9306), in MDC 19 (Mental Diseases and Disorders), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific psychological disorder codes (official index)
- associated with
- disease classified elsewhere F54 — Psychological and behavioral factors associated with disorders or diseases classified elsewhere
- sexual
- development F66 — Other sexual disorders
- relationship F66 — Other sexual disorders
- uncertainty about gender identity F64.9 — Gender identity disorder, unspecified
Don't confuse with (Excludes1 for F99)
- unspecified mental disorder due to known physiological condition (F09)
Common questions about psychological disorder ICD-10 codes
What is the ICD-10 code for psychological disorder?
- F99 — Mental disorder, not otherwise specified. More specific codes apply when the documentation supports them: F54, F66, F66, F64.9.
Is F99 billable?
- Yes. F99 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can F99 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict F99 as a principal diagnosis.
Is F99 a CC or MCC?
- No. F99 is neither a CC nor an MCC under MS-DRG v44.0.