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Osmolar Gap (Elevated) Differential Diagnosis

Normal Osmolar Gap: < 15

    Acetone
    • Associations:  Ingestion of isopropanol +/- inebriation + no anion gap + no metabolic acidosis
    • Pathophysiology:  Isopropanol is metabolized to acetone.
    Ethanol

    • Associations:  Alcohol ingestion + inebriation + no anion gap (unless AKA present) + no metabolic acidosis (unless AKA present)
    • Pathophysiology:  It is an alcohol.
    Ethylene Glycol (Antifreeze)

    • Associations:  Antifreeze ingestion/suicide attempt + anion gap metabolic acidosis +/- renal impairment
    • Pathophysiology:  Ethylene glycol gets metabolized to eventually for glycolic acid and oxalic acid.
    Isopropranol

    • Associations:  Ingestion +/- inebriation + no anion gap (if only ingestion)
    • Pathophysiology:  It is an alcohol and metabolized to acetone.
    Mannitol

    • Associations:  IV infusion of mannitol
    • Pathophysiology:  An organic substance that absorbs water.
    Methanol

    • Associations:  Reports of ingestion +/- metabolic acidosis +/- changes in vision
    • Pathophysiology:  Methanol is metabolized to formic acid.
    Osmotic Contrast Dye

    • Associations:  IV contrast for imaging.
    • Pathophysiology:  Increased osmolarity.
    Propylene Glycol

    • Associations:  Use of lorazepam (Ativan) or Dilantin infusions
    • Pathophysiology:  It is an organic substance that absorbs water.
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    Editors & Reviewers

    Editors:

    • Anthony J. Busti, MD, PharmD, FNLA, FAHA

    Last Reviewed:  August 2015