ICD-10 Code F03.C18 – Unspecified dementia, severe, with other behavioral disturbance (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code F03.C18 – Unspecified dementia, severe, with other behavioral disturbance
What it is
This code identifies severe dementia when the type is not specified and the patient has behavioral disturbance. Use it when documentation supports dementia with significant impairment, but does not name a more specific dementia subtype.
Clinical signs
Clinical features vary; refer to documentation. Commonly, severe dementia includes marked memory loss, poor orientation, and major dependence in daily activities, along with behavioral symptoms such as agitation, wandering, or other disruptive behavior.
When to use this code
Use this code when the provider documents unspecified dementia and also states the dementia is severe with behavioral disturbance. It fits records that describe advanced cognitive decline plus behavior problems, but do not identify Alzheimer’s disease, vascular dementia, or another specific cause. Check documentation if severity or behavior is unclear.
Do not use for
Do not use this code if the dementia type is specified and a more specific code applies. Do not use it when behavioral disturbance is absent or when the record only supports mild or moderate dementia.
Coding tip
Confirm both “severe” and “with other behavioral disturbance” are documented before assigning F03.C18.