Sodium Correction Rate Calculator for Hypo- and Hypernatremia

Created by Małgorzata Koperska, MD and Dominika Śmiałek, MD, PhD candidate
Reviewed by Bogna Szyk and Steven Wooding
Based on research by
Adrogué HJ, Madias NE Hyponatremia The New England Journal of Medicine (May 2000)
Last updated: Aug 17, 2022

The sodium correction rate calculator uses the patient's weight, serum sodium concentration, the aimed increase of serum sodium, and the chosen fluid's parameters to find the serum sodium change per liter and the rate of the sodium replacement fluid flow.

Read on to see what sodium replacement formula we used. You'll also probably find our water deficit, sodium deficit, sodium correction for hyperglycemia, or fractional excretion of sodium (FENa) calculators useful.

We do our best to make our calculators reliable and precise. Remember, though – Omni Calculator is not a doctor! Make sure you know the correct dose before administering any drugs to your patients.

What's the sodium replacement rate formula?

The sodium correction rate calculator uses the Adrogue-Madias formula, as it is the one most widely used in the prediction of serum sodium change:

sodium sodium change = (fluid_sodium - serum_sodium) / (TBW + 1)

where:

  • fluid_sodium – Concentration of sodium in the fluid you're planning to use – the values provided here are based on this table of the composition of commonly used crystalloids by the National Institute for Health and Care Excellence (NICE);

  • serum_Na – Measured concentration of sodium in the blood serum.

  • TBWTotal body water. We calculate this by multiplying the patient's weight by the age/sex coordinate, which equals: 60% for children and adult males, 50% for adult females and elderly males, and 45% for elderly females.

Then, to calculate the sodium correction rate, we use the inverse of the previous calculation, with the option of adding the level of potassium in the fluid into the equation:

correction flow rate = 1000 × aimed_change × (TBW + 1) / (fluid_sodium + fluid_potassium - serum_sodium)

where:

  • aimed_change – Aimed serum sodium change per hour. As there is a risk of overcorrection; and

  • fluid_potassium – Concentration of potassium in the fluid you're planning to use.

How to calculate the sodium replacement rate?

  1. Choose the patient's age/sex group from the five options given in the first line: child, adult female, adult male, elderly female, and elderly male.

  2. Type in the patient's weight in the preferred unit.

  3. Enter the measured serum sodium level. If your results are in mmol/L, type in these values – in the case of sodium, they are equal to those in mEq/L.

  4. Choose the kind of sodium replacement fluid you're planning to use.

  5. If the chosen fluid contains potassium, enter its concentration. According to the table mentioned above, it's 4 mEq/L (or mmol/L) in lactated Ringer's, and 5 mEq/L (mmol/L) in Ringer's acetate.

  6. The predicted serum sodium change per liter of administered replacement fluid is given in the second to last field in milliequivalents per liter (mEq/L), which are equal to millimoles per liter (mmol/L).

  7. The calculated sodium correction rate is presented in the last field in milliliters per hour (ml/h).

Małgorzata Koperska, MD and Dominika Śmiałek, MD, PhD candidate
Age/sex category
Adult male
Weight
lb
Serum sodium
mEq/L
Fluid sodium
0.9% NaCl (154 mmol/L)
Fluid potassium
mEq/L
Aimed serum sodium change per hour
mEq/L/h
Sodium change per liter
mEq/L
Correction rate
mL/h
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