This version was machine-translated from German and has not been medically reviewed. The authoritative version is the German version.
Effective osmolality (tonicity)
2 × sodium + glucose – the osmotically effective osmolality without urea
Calculation aid for healthcare professionals: the calculator reproduces what the sources cited assign to the inputs. Clinical assessment and every treatment decision remain with the treating physician. Inputs and results are not stored.
Frequently asked questions
Effective osmolality (tonicity): What does this calculator compute?
Calculates effective osmolality (tonicity) from sodium and glucose (2 × Na + glucose/18 or + glucose in mmol/l) – the quantity that determines fluid shifts between compartments, for example in diabetic ketoacidosis and hyperosmolar decompensation.
Effective osmolality (tonicity): Which sources is this calculator based on?
Rasouli M: Basic concepts and practical equations on osmolality: Biochemical approach (Clin Biochem 49:936–941) (2016); Purssell RA, Pudek M, Brubacher J, Abu-Laban RB: Derivation and validation of a formula to calculate the contribution of ethanol to the osmolal gap (Ann Emerg Med 38:653–659) (2001)