ICD-10 Guide

Acute Delirium

ICD-10 Coding for Acute Delirium(F05, F05.9)

PRIMARY SPECIALTYInternal Medicine

COMPLEXITYHigh

LAST UPDATED09/15/2025

Sam Tuffun, PT, DPT

Physical Therapist | Medical Coding & Billing Contributor

Diagnosis Overview

What is Acute Delirium?

Acute delirium is a rapid-onset, fluctuating disturbance in attention and cognition, often resulting from an underlying medical condition. Key clinical points include: 1) It can be caused by metabolic imbalances, infections, or substance withdrawal. 2) Symptoms may include confusion, disorientation, and altered levels of consciousness. 3) It is often reversible if the underlying cause is identified and treated promptly. Typical use cases for this diagnosis code include hospital admissions for elderly patients presenting with sudden confusion or altered mental status. The etiology often involves multifactorial causes such as dehydration, infections, or medication effects. Pathophysiologically, acute delirium is linked to neurotransmitter imbalances and inflammation in the brain. Clinically, patients may exhibit fluctuating levels of awareness and attention, which can complicate their overall medical management.

Key Clinical Considerations:

Diagnosis requires evidence of an acute change in attention and cognition, with a duration of hours to days.
Signs and symptoms include disorientation, inability to focus, perceptual disturbances, and fluctuating levels of consciousness.
Resolution criteria involve the return to baseline cognitive function after treatment of the underlying cause.
Laboratory findings may include electrolyte imbalances, infections indicated by elevated white blood cell counts, or imaging results showing no acute intracranial pathology.

Clinical Information

Clinical Criteria & Documentation Requirements

Documentation must clearly state the diagnosis of acute delirium, including the underlying cause if known.
Compliant documentation includes detailed descriptions of the patient's mental status changes and any diagnostic tests performed.
Template phrases include: 'Patient diagnosed with acute delirium secondary to [underlying condition]' or 'Mental status changes observed during hospitalization.'
Medical necessity documentation should justify the need for hospitalization or further evaluation based on the severity of symptoms.

Coding Guidelines

Usage Guidelines & Examples

Use this code when a patient presents with acute confusion due to a reversible cause, such as infection or medication effects.
Do not use this code for chronic cognitive disorders like dementia or when the confusion is due to a primary psychiatric condition.
Correct usage example: 'Patient admitted with acute delirium secondary to urinary tract infection.' Incorrect usage: 'Patient with a history of dementia presenting with confusion.'
Common errors include misclassifying acute delirium as a chronic condition; ensure the acute nature is documented.

Code Exclusions

Important Exclusions

Excluded conditions include chronic neurocognitive disorders like Alzheimer's disease, as they are not acute.
Alternative codes for exclusions may include F00 (Dementia in Alzheimer's disease) for chronic conditions.
Common exclusion errors involve misdiagnosing chronic conditions as acute; ensure clarity in documentation.
Certain conditions are excluded to maintain specificity in coding and to avoid misrepresentation of the patient's status.

Specialty Focus

Primary Specialty

Internal Medicine

Specialty Applications

This diagnosis applies to patients experiencing acute confusion due to reversible medical conditions.
Clinical scenarios include elderly patients in acute care settings presenting with sudden cognitive changes.
Applicable in various practice settings, including inpatient, outpatient, and emergency departments.
Specialty-specific considerations include the need for geriatric assessments in elderly patients.

Coding Complexity

High Complexity

This diagnosis requires careful attention to:

Comprehensive clinical documentation
Accurate code selection based on clinical criteria
Proper exclusion considerations
Specialty-specific coding guidelines

Documentation

Documentation Templates

Template 1

Template: 'Acute delirium diagnosed based on clinical findings of confusion and disorientation.'

Template 2

Template: 'Patient presents with acute confusion consistent with delirium secondary to [underlying condition].'

Template 3

Template: 'Diagnostic criteria met: acute change in attention and cognition observed.'

Template 4

Template: 'Treatment plan includes hydration and antibiotics for urinary tract infection causing delirium.'

Billing Information

Billing Considerations

Ensure proper documentation for billing
Verify code specificity requirements
Check for any additional codes needed
Review payer-specific guidelines

Common Issues

Insufficient clinical documentation
Incorrect code selection
Missing supporting diagnoses
Timing and frequency documentation

Frequently Asked Questions

What documentation is required for this code?

Detailed documentation of acute changes in mental status, including assessments and underlying causes.

When should this code be used vs similar codes?

Use this code for acute, reversible conditions; similar codes apply to chronic cognitive disorders.

What are common billing issues with this code?

Issues may arise from lack of clear documentation of the acute nature of the condition.

What procedures are commonly associated?

Related CPT codes include those for mental status examinations and diagnostic imaging as medically necessary.

What is Acute Delirium?

Key Clinical Considerations:

Diagnosis requires evidence of an acute change in attention and cognition, with a duration of hours to days.
Signs and symptoms include disorientation, inability to focus, perceptual disturbances, and fluctuating levels of consciousness.
Resolution criteria involve the return to baseline cognitive function after treatment of the underlying cause.
Laboratory findings may include electrolyte imbalances, infections indicated by elevated white blood cell counts, or imaging results showing no acute intracranial pathology.

Acute Delirium

Diagnosis Overview

Key Clinical Considerations:

Clinical Information

Clinical Criteria & Documentation Requirements

Coding Guidelines

Usage Guidelines & Examples

Code Exclusions

Important Exclusions

Related ICD-10 Codes

Related CPT Codes

Specialty Focus

Primary Specialty

Specialty Applications

Coding Complexity

Documentation

Documentation Templates

Template 1

Template 2

Template 3

Template 4

Billing Information

Billing Considerations

Common Issues

Frequently Asked Questions

What documentation is required for this code?

When should this code be used vs similar codes?

What are common billing issues with this code?

What procedures are commonly associated?

Acute Delirium

Diagnosis Overview

Key Clinical Considerations:

Clinical Information

Clinical Criteria & Documentation Requirements

Coding Guidelines

Usage Guidelines & Examples

Code Exclusions

Important Exclusions

Related ICD-10 Codes

Related CPT Codes

Specialty Focus

Primary Specialty

Specialty Applications

Coding Complexity

Documentation

Documentation Templates

Template 1

Template 2

Template 3

Template 4

Billing Information

Billing Considerations

Common Issues

Frequently Asked Questions

What documentation is required for this code?

When should this code be used vs similar codes?

What are common billing issues with this code?

What procedures are commonly associated?