F09Unspecified mental disorder due to known physiological condition

F09 is the ICD-10-CM diagnosis code for unspecified mental disorder due to known physiological condition. It belongs to block F01-F09 (mental disorders due to known physiological conditions) and chapter 5 (mental, Behavioral and Neurodevelopmental disorders). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Don't report F09 together with the conditions in its Excludes1 note: mild neurocognitive disorder due to known physiological condition (F06.7-) and psychosis NOS (F29).

Code first: the underlying physiological condition.

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 884 (Organic Disturbances and Intellectual Disability, relative weight 1.6001), DRG 974 (HIV with Major Related Condition with MCC, relative weight 3.0506), DRG 975 (HIV with Major Related Condition with CC, relative weight 1.3252) and DRG 976 (HIV with Major Related Condition without CC/MCC, relative weight 0.8124), in MDC 19 (Mental Diseases and Disorders) and MDC 25 (Human Immunodeficiency Virus Infections), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 310.9 (unspecified nonpsychotic mental disorder following organic brain damage).