ICD-10-CM 2027
ICD-10 code for mental disorder
From the official ICD-10-CM alphabetic index entry “Disorder (of) › mental (or behavioral) (nonpsychotic)”. Page updated September 29, 2026.
About coding mental disorder
The ICD-10-CM code for mental disorder is F99 (Mental disorder, not otherwise specified). The official index lists 12 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 mental disorder codes (official index)
- due to (secondary to)
- amphetamine
- due to drug abuse
- due to drug dependence
- brain disease, damage and dysfunction F09 — Unspecified mental disorder due to known physiological condition
- caffeine use
- due to drug abuse
- due to drug dependence
- cannabis use
- due to drug abuse
- due to drug dependence
- general medical condition F09 — Unspecified mental disorder due to known physiological condition
- sedative or hypnotic use
- due to drug abuse
- due to drug dependence
- tobacco (nicotine) use
- following organic brain damage F07.9 — Unspecified personality and behavioral disorder due to known physiological condition
- frontal lobe syndrome F07.0 — Personality change due to known physiological condition
- personality change F07.0 — Personality change due to known physiological condition
- postconcussional syndrome F07.81 — Postconcussional syndrome
- specified NEC F07.89 — Other personality and behavioral disorders due to known physiological condition
- infancy, childhood or adolescence F98.9 — Unspecified behavioral and emotional disorders with onset usually occurring in childhood and adolescence
- neurotic
- organic or symptomatic F09 — Unspecified mental disorder due to known physiological condition
- presenile, psychotic F03 — Unspecified dementia
- problem NEC
- psychoneurotic
- psychotic
- puerperal F53.0 — Postpartum depression
- senile, psychotic NEC F03 — Unspecified dementia
Don't confuse with (Excludes1 for F99)
- unspecified mental disorder due to known physiological condition (F09)
Common questions about mental disorder ICD-10 codes
What is the ICD-10 code for mental disorder?
- F99 — Mental disorder, not otherwise specified. More specific codes apply when the documentation supports them: F09, F09, F07.9, F07.0 and others below.
What is the ICD-10 code for organic or symptomatic mental disorder?
- F09 — Unspecified mental disorder due to known physiological condition.
What is the ICD-10 code for puerperal mental disorder?
- F53.0 — Postpartum depression.
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.