Internal Medicine · Emergency Medicine · Nephrology

Calculated Serum Osmolality (2×Na) calculator

Enter the published formula inputs below to calculate and interpret this score.

Clinical inputs

Serum sodium (mmol/L)

Serum glucose (mg/dL)

Blood urea nitrogen (mg/dL)

Result

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Formula inputs

Serum sodium (mmol/L)Accepted range: 100 to 180
Serum glucose (mg/dL)Accepted range: 0 to 1200
Blood urea nitrogen (mg/dL)Accepted range: 0 to 200

Primary source

Smithline N et al. Calculated osmolality in the assessment of acid-base disorders. Am J Med. DOI: 10.1016/0002-9343(76)90404-9. PMID: 941150. Scope: calculated serum osmolality (mOsm/kg) ≈ 2 × sodium + glucose/18 + BUN/2.8 when sodium is in mmol/L and glucose and BUN are in mg/dL. (1976)

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