Stephen J. Schueler, M.D.


Lethargy Overview

What is lethargy?
A person with lethargy has impaired mental ability that manifests as excessive sleepiness. Many with severe lethargy are unable to think clearly. Lethargy may be caused by drug intoxication, drug side effect, poisoning, head injury, meningitis, encephalitis, low blood sugar, low blood oxygen, seizure, brain tumor, or a severe metabolic derangement.

What are the symptoms of lethargy?
Symptoms depend on the underlying cause for the lethargy. Symptoms that may be associated with lethargy include: confusion, anxiety, difficulty speaking, difficulty walking, hallucinations, depression, loss of memory, and other neurological symptoms.

How does the doctor diagnose lethargy?
The doctor can diagnose lethargy after taking your history and performing an examination. Testing is often required to determine the underlying cause for the lethargy. Testing may include CT scanning of the brain, MRI scanning of the brain, EEG, lumbar puncture, and brain biopsy. Other tests include serum glucose, thyroid profile, electrolyte profile, serum thiamine, and serum folate level.

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