Calc Function

    • Calcs that help predict probability of a diseaseDiagnosis
    • Subcategory of 'Diagnosis' designed to be very sensitiveRule Out
    • Disease is diagnosed: prognosticate to guide treatmentPrognosis
    • Numerical inputs and outputsFormula
    • Med treatment and moreTreatment
    • Suggested protocolsAlgorithm





    Chief Complaint


    Organ System


    Patent Pending

    Sodium Deficit in Hyponatremia

    Calculates sodium quantity missing in hyponatremia.
    Why Use

    Estimates the total amount of sodium that needs to be replaced in hyponatremia patients.



    Please fill out required fields.

    Next Steps
    Creator Insights


    Correct hyponatremia carefully. Do not forget to correct the hyponatremia level in hyperglycemic patients with the Sodium Correction for Hyperglycemia calculator. Use with the Sodium Correction Rate in Hyponatremia calculator which estimates the rate to correct, as well as tonicity of the solution used. Typically hypertonic solutions are reserved for patients that are overly symptomatic, such as seizures and severe neurologic deficits.


    Sodium deficit = total body water × (desired Na - pt's Na)

    For adults, total body water (TBW) is calculated using the Watson equation:

    • Men: TBW, liters = 2.447 – 0.09516 × age, years + 0.1074 × height, cm + 0.3362 × weight, kg
    • Women: TBW, liters = -2.097 + 0.1069 × height, cm + 0.2466 × weight, kg

    For children, TBW = 0.6 × weight, kg

    Facts & Figures

    Remember not to correct too rapidly to avoid central pontine myelinolysis!

    You can use the hyponatremia correction rate calculator to pick an appropriate fluid and volume as well.

    Dr. Nicolaos E. Madias

    About the Creator

    Nicolaos E. Madias, MD is the chair of the department of medicine at the St. Elizabeth's Medical Center and a professor of medicine, specializing in Nephrology, at Tufts University School of Medicine. He has co-authored over 100 articles published in peer reviewed journals.

    To view Dr. Nicolaos E. Madias's publications, visit PubMed