Last updated: April 6, 2026, 6:50 PM Pacific Time (PDT)
Symptom-first framework for acute confusion, delirium, agitation, somnolence, or coma. Stabilize first, then separate toxic-metabolic, infectious, neurologic, seizure-related, intoxication or withdrawal, and psychiatric mimics.
AllImmediate stabilizationToxic / metabolicNeurologic / structuralInfectiousBack to Main Page
Interactive diagnostic assistant
Activate the assistant to re-rank likely causes of altered mental status as data is entered.
Presentation
Neurologic clues
Systemic clues
Toxic and bedside clues
Likely diagnoses from entered data
Recommended next labs, imaging, and diagnostics
Flowchart
First Pass
Altered mental status is a syndrome, not a diagnosis
Clarify delirium, reduced arousal, agitation, psychosis, or coma. Stabilize ABCs, check glucose early, and look for reversible causes before refining the differential.
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Immediate stabilization
Treat time-sensitive causes first
Glucose, hypoxia, opioid toxicity, shock, and ongoing seizure should move ahead of a broad workup.
Toxic / metabolic
Common bucket
Toxic-metabolic encephalopathy
Glucose disorders, sodium disorders, organ failure, hypercarbia, and medication effect commonly cause diffuse brain dysfunction.
Exposure clues
Intoxication, overdose, or withdrawal
Think opioids, sedatives, alcohol withdrawal, toxidromes, and polypharmacy.
Neurologic / structural
Focal or abrupt
Stroke, hemorrhage, mass effect, or trauma
Focal deficits, sudden onset, headache, or trauma should accelerate neuroimaging.
Occult possibility
Post-ictal state or nonconvulsive seizure
Persistent unexplained AMS may still be seizure-related and need EEG-focused thinking.
Infectious and inflammatory
Systemic infection
Sepsis-associated delirium
Older or medically complex patients may present with confusion as the first sign of systemic infection.
Fever + headache + neck stiffness
Meningitis or encephalitis
CNS infection stays high on the list when fever, meningismus, seizure, or severe headache accompany confusion.
Diagnosis of exclusion
Fluctuating attention
Delirium framework
Acute inattention and fluctuating cognition usually imply a medical cause until proven otherwise.
After medical screening
Primary psychiatric syndrome
Psychiatric causes usually remain diagnoses of exclusion in undifferentiated acute AMS.