U.S. ICD-10-CM · FY 2027

F99 ICD-10-CM Code: Mental disorder, not otherwise specified

A clear reference for the official code description, hierarchy, and related coding information from the FY 2027 U.S. release.

Code definition

Official description

F99

Mental disorder, not otherwise specified

ICD-10-CM diagnosis code · United States clinical modification

Classification

Where F99 sits

  1. 1

    Chapter 5

    Mental, Behavioral and Neurodevelopmental disorders (F01-F99)

  2. 2

    Section

    Unspecified mental disorder (F99)

  3. 3

    Category F99

    Mental disorder, not otherwise specified

  4. 4

    Code F99

    Mental disorder, not otherwise specified

Documentation details

Notes for this code

Inclusion terms

  • Mental illness NOS

Code first

No “code first” instruction is listed for F99.

Use additional code

No “use additional code” instruction is listed for F99.

Excludes1

Conditions that should not be reported together with this code.

  • unspecified mental disorder due to known physiological condition (F09)

Excludes2

Conditions not included here that may be reported separately when present.

No Excludes2 note is listed for F99.

Transparency

Source and release

Data release

U.S. ICD-10-CM · FY 2027

Effective date

Oct 1, 2026

Publisher

Vero Scribe Inc.

This reference is generated from Vero’s ICD-10-CM description, hierarchy, and code-note dataset. The visible content and structured data share that source.

Review the CDC/NCHS ICD-10-CM source

Code-specific guidance

Frequently asked questions

What does ICD-10-CM code F99 mean?

F99 is the FY 2027 U.S. ICD-10-CM code for “Mental disorder, not otherwise specified.”

Is F99 a billable or specific ICD-10-CM code?

Yes. In the FY 2027 reference data used on this page, F99 has no child codes and is presented as a billable/specific code. Always confirm the active code set and payer requirements before use.

Where is F99 located in ICD-10-CM?

F99 is listed in Chapter 5, Mental, Behavioral and Neurodevelopmental disorders (F01-F99), within Unspecified mental disorder (F99) (F99–F99), under category F99, Mental disorder, not otherwise specified.

What coding notes are listed for F99?

Its listed inclusion terms are Mental illness NOS. No code-first instruction is listed. Excludes1 notes: unspecified mental disorder due to known physiological condition (F09). No Excludes2 note is listed.

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