F99
Billable codeMental disorder, not otherwise specified
The ICD-10 code for mental disorder, not otherwise specified is F99.
Clinical notes
Excludes1 (not coded here)
An Excludes1 note is a pure exclusion: the excluded condition and this code should never be reported together, because the two conditions cannot occur at the same time (e.g. a congenital form vs. an acquired form of the same disease).
- unspecified mental disorder due to known physiological condition (F09)
Also known as
Alternate wording, synonyms, or specific conditions that fall under this code, listed to help confirm you've picked the right one.
- Mental illness NOS
Documentation support
General coding-documentation guidance — not a substitute for payer-specific requirements or professional coding judgment.
- •Confirm the excluded condition(s) listed above are not also present — Excludes1 conditions cannot be coded together with this one.
- •As a general rule, code to the highest level of specificity supported by the documentation in the medical record.
ICD-9-CM equivalent
Informational only — GEM mappings are approximate, not guaranteed one-to-one equivalents. Verify before use in billing.
- 3009Approximate match
Associated MS-DRGs
F99 can serve as the principal diagnosis for these Medicare Severity Diagnosis-Related Groups.
Informational only — actual DRG assignment also depends on procedures, complications/comorbidities (CC/MCC), discharge status, and payer-specific rules not reflected here.