ICD-10 Code F04: Amnestic disorder due to known physiological condition

Key Takeaways

ICD-10 Code F04 is a billable diagnosis code for amnestic disorder due to a known physiological condition, valid for 2026 ICD-10-CM.

The underlying physiological cause (such as Korsakoff syndrome, TBI, or hypoxic brain injury) must be documented and coded separately alongside F04.

F04 has strict Type 1 Excludes notes: amnesia NOS (R41.3), anterograde amnesia (R41.1), retrograde amnesia (R41.2), and dissociative amnesia (F44.0) cannot be used in place of F04.

Pabau’s mental health EMR supports structured clinical documentation and claims management to reduce F04 coding errors and claim denials.

ICD-10 Code F04 is the billable diagnosis for amnestic disorder due to a known physiological condition — used when memory loss following a stroke, brain injury, or thiamine deficiency has a documented physiological cause. Defaulting to R41.3 (amnesia NOS) in these cases risks claim denials, audit flags, and clinical records that misrepresent the patient’s condition.

This reference guide covers the clinical definition of F04, its diagnostic criteria, excludes notes, documentation requirements, related codes, and billing considerations for the 2026 ICD-10-CM fiscal year.

ICD-10 code F04: definition and clinical description

ICD-10 Code F04 describes a persistent amnestic disorder caused by a known physiological condition. The code sits within the F01-F09 block, titled “Mental disorders due to known physiological conditions,” in the ICD-10-CM classification system maintained by the Centers for Medicare and Medicaid Services (CMS) and the National Center for Health Statistics (NCHS).

F04 captures the clinical reality of organic amnesia: the patient shows significant impairment in acquiring new memories (anterograde amnesia), recalling past memories (retrograde amnesia), or both. The disorder must be directly attributable to a documented medical cause, not to a psychiatric or dissociative process.

Confabulation is listed as an included manifestation under F04. This means fabricated or distorted memories arising from the amnestic disorder do not require a separate diagnosis code. They are captured within F04 itself.

Code details at a glance

Diagnostic criteria for F04

F04 applies when a patient presents with significant memory impairment and a known physiological cause can be identified and documented. The disorder must not be better explained by delirium, dementia, or a dissociative process.

Clinicians diagnosing F04 typically observe one or more of the following memory deficits.

• Anterograde amnesia: Inability to form new memories after the onset of the physiological event. The patient cannot retain information beyond a few minutes despite normal alertness.
• Retrograde amnesia: Impaired recall of events that occurred before the physiological insult. The temporal gradient can range from days to years.
• Confabulation: The patient produces unintentional, fabricated recollections to fill memory gaps. This is a positive symptom of the amnestic state, not a separate psychiatric condition.
• Relatively preserved procedural memory: Many patients retain motor and skill-based learning even when episodic memory is severely disrupted.

The physiological cause must be documented explicitly. A note that a patient “has memory problems” is not sufficient for F04. The record must name the specific underlying condition and establish a causal link.

Common physiological causes

These are the conditions most frequently documented as the underlying cause when coding F04. Per the F01-F09 coding pattern, the underlying condition is always coded separately and listed first.

• Korsakoff syndrome: Thiamine deficiency, typically from chronic alcohol use or malnutrition, causing dense anterograde amnesia with confabulation. The most classic clinical presentation of F04.
• Traumatic brain injury (TBI): Post-traumatic amnesia following moderate or severe TBI, once post-traumatic delirium has resolved.
• Hypoxic brain injury: Anoxic or hypoxic events (cardiac arrest, respiratory failure) resulting in selective hippocampal damage and persistent memory deficits.
• Herpes simplex encephalitis: Limbic encephalitis causing disproportionate memory impairment relative to other cognitive functions.
• Wernicke encephalopathy: Acute-phase thiamine deficiency that, if not fully treated, progresses to Korsakoff-type chronic amnestic disorder.
• Surgical procedures with hypoxia: Prolonged intraoperative hypoxia resulting in hippocampal injury and amnestic sequelae.

F04 excludes notes and differential coding

F04 carries Type 1 Excludes notes covering four codes that are not interchangeable with it. Symptom-level codes and disorder-level codes occupy distinct places in the classification hierarchy, and mixing them is a common source of denials.

Type 1 Excludes (cannot be used together with F04)

A Type 1 Excludes note means the excluded code and F04 describe mutually exclusive conditions. You cannot apply both codes to the same encounter. If the chart documents amnesia without a confirmed physiological etiology, R41.3 applies. When a physiological cause is identified and documented, ICD-10 Code F04 is the correct assignment.

F04 vs. R41.3: choosing the right code

R41.3 is a symptom code: it records that amnesia is present but does not explain why. F04 is a disorder code: it records that amnesia exists because of a documented physiological mechanism.

Use R41.3 when: the cause of amnesia has not been determined at the time of the encounter, or the patient is still undergoing diagnostic workup. Use F04 when: the clinical record explicitly names the physiological cause and the treating clinician has established the causal relationship in their documentation.

F04 vs. F06.7: related codes in the F01–F09 block

F06.7 describes mild neurocognitive disorder due to a known physiological condition. The distinction from F04 is severity and specificity: F06.7 covers broader, milder cognitive decline without the specific profile of amnestic disorder. When memory impairment is the dominant feature and meets the threshold for amnestic disorder, F04 is more specific and should be preferred. Consult the CDC/NCHS ICD-10-CM web tool to confirm code specificity before finalizing assignment.

Documentation requirements for F04

Insufficient documentation is the primary driver of F04 claim denials. The record must establish both the diagnosis and its cause. For F04, these are the required documentation elements.

• Named physiological condition: The underlying cause (e.g., Korsakoff syndrome, hypoxic brain injury) must be explicitly stated, not implied. “History of alcohol use” is not the same as “Korsakoff syndrome.”
• Causal relationship: The clinician’s note must establish that the amnestic disorder is a direct result of the named physiological condition. Language like “amnestic disorder secondary to [condition]” or “amnestic disorder due to [condition]” satisfies this requirement.
• Memory impairment description: The record should document the specific nature of the memory deficit (anterograde, retrograde, or both), its severity, and its functional impact on the patient.
• Exclusion of delirium and dementia: Documentation should clarify that the amnestic symptoms are not part of an active delirium state or a broader dementia syndrome, as these have their own coding categories.
• Code sequencing: Per ICD-10-CM instructional notes, the underlying physiological condition is coded first. F04 is sequenced as an additional code, never as the principal diagnosis in isolation.

Neuropsychological testing and F04

Neuropsychological testing results strengthen F04 documentation significantly. Formal memory assessments quantify the impairment, establish a baseline, and support medical necessity for both the diagnosis and related services. When available, reference the specific test used (e.g., Wechsler Memory Scale, Rey Auditory Verbal Learning Test), the score obtained, and the clinician’s interpretation linking results to the physiological cause.

Payers auditing F04 claims will look for this chain: physiological condition documented, causal relationship established, memory impairment described and quantified. A structured psychiatric evaluation template can help clinicians capture each of these elements consistently across encounters.

Reduce F04 claim denials with complete documentation

Pabau's clinical documentation and claims management tools help practices build the complete paper trail payers require for complex diagnosis codes like F04. Structured forms, automated workflows, and integrated billing support accurate coding from the first encounter.

Book a demo

Billing and reimbursement considerations for F04

F04 is a valid, billable ICD-10-CM code for 2026. It can support claims for evaluation and management services, neuropsychological testing, cognitive rehabilitation, and ongoing psychiatric or neurological management. However, payer policies vary, and patient care management workflows need to reflect these differences to avoid repeated denials.

Medicare and Medicaid considerations

Medicare generally covers services billed with F04 when medical necessity is documented. The CMS ICD code lists confirm F04’s validity for Section 111 reporting. Key factors that affect coverage decisions include whether the underlying physiological condition is also coded and sequenced correctly, and whether the services billed align with the documented severity of the amnestic disorder.

Medicaid coverage policies for cognitive and psychiatric diagnoses differ by state. Practices billing F04 for Medicaid patients should verify their state’s Local Coverage Determinations and any prior authorization requirements before submitting claims.

Common billing errors with F04

• Using R41.3 when F04 is supported: If documentation establishes a physiological cause, coding amnesia as NOS is under-coding. This leaves revenue on the table and misrepresents the patient’s condition.
• Missing the underlying condition code: Submitting F04 without the code for the physiological cause (e.g., Korsakoff syndrome, TBI) violates coding sequencing rules and triggers denials.
• Conflating F04 with dementia codes: When a patient has both amnestic disorder and dementia, the more specific dementia code typically takes precedence. F04 should not be applied when the memory impairment is fully explained by the dementia diagnosis.
• Separately coding confabulation: Confabulation is an included manifestation of F04. Applying a separate code for it creates an invalid code combination that payers will flag.

Practices using claims management software with built-in coding validation can catch these errors before submission. Integrated digital intake forms that prompt clinicians to document etiology at the point of care improve alignment between clinical documentation and billing accuracy.

Related codes and ICD-9-CM crosswalk

Understanding the full code family around F04 helps coders select the most appropriate code and avoid assigning a less specific diagnosis when the documentation supports greater precision. The AAPC Codify ICD-10-CM lookup provides a searchable index of all F01-F09 codes with excludes notes, instructional notes, and crosswalks in one view.

Key related codes

ICD-9-CM crosswalk

The approximate ICD-9-CM equivalent for ICD-10 Code F04 is 294.0 (Amnestic disorder in conditions classified elsewhere). This crosswalk is approximate and requires clinical interpretation. The ICD-10-CM system allows greater specificity in documenting the underlying physiological condition separately, which the ICD-9-CM single-code approach did not accommodate as precisely. Reference the ICD List for free bidirectional ICD-9/ICD-10 crosswalk searches.

Practices transitioning historical records or handling legacy claims should treat this crosswalk as a starting point, not a direct equivalency. The psychiatry EMR software used at your practice should support both code sets if you are managing patients with records spanning the 2015 ICD-10 transition.

Conclusion

ICD-10 Code F04 is specific where R41.3 is not, and that specificity matters for claim accuracy, payer audits, and clinical records that accurately reflect the patient’s condition. The code works only when documentation names the physiological cause, establishes the causal link, and sequences the underlying condition first.

Pabau’s clinical documentation tools help practices build structured records that capture every element payers require, from etiology to functional impact, reducing the back-and-forth of F04 denials. To see how Pabau supports mental health and neurology coding workflows, book a demo.

Continue your research

Working with other psychiatric ICD-10 codes? ICD-10 code for autistic disorder covers the F84 code family and documentation requirements for autism spectrum diagnoses.

Need help structuring clinical evaluations? Psychiatric evaluation template provides a step-by-step framework for comprehensive mental health assessments that supports accurate diagnosis coding.

Managing mental health billing workflows? Mental health EMR from Pabau supports structured documentation, claims management, and coding accuracy for behavioral health practices.

Frequently asked questions