The osmolar gap represents the difference between measured and calculated serum osmolality, serving as a crucial diagnostic parameter in clinical medicine. This gap indicates the presence of unmeasured osmoles in the blood, which can be vital for detecting toxic alcohol ingestion, metabolic disorders, and other pathological conditions.

Normal serum osmolality ranges from 280-295 mOsm/kg H₂O and is primarily determined by sodium salts, glucose, and urea. When additional unmeasured substances are present, they contribute to the total osmolality, creating a gap between measured and calculated values.

A normal osmolar gap is typically less than 10 mOsm/kg H₂O. Values exceeding this threshold warrant clinical investigation, particularly in cases of suspected toxic alcohol ingestion, severe metabolic acidosis, or unexplained altered mental status.

Step 1: Enter Measured Osmolality

Input the measured serum osmolality value obtained from laboratory analysis. This value is typically measured using freezing point depression or vapor pressure osmometry and should be expressed in mOsm/kg H₂O.

Step 2: Input Laboratory Values

Enter the serum sodium level in mEq/L or mmol/L, glucose concentration in mg/dL, and blood urea nitrogen (BUN) level in mg/dL. Ensure all values are from the same blood sample taken simultaneously for accurate calculation.

Step 3: Calculate and Interpret Results

Click the calculate button to obtain the osmolar gap value. The calculator will display the result along with detailed calculation steps and clinical interpretation based on established reference ranges.

Step 4: Review Clinical Significance

Analyze the provided interpretation and potential causes if the osmolar gap is elevated. Consider the clinical context, patient history, and symptoms when evaluating results for appropriate diagnostic and therapeutic decisions.