Sodium Correction Rate Calculator for Hypo- and Hypernatremia

By Małgorzata Koperska, MD
Last updated: Aug 11, 2021

The sodium correction rate calculator uses the patient's weight, their 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 make our best to make our calculators reliable and precise. Remember though - Omni Calculator is not a doctor! Make sure you know the right 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 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 composition of commonly used crystalloids by the National Institute for Health and Care Excellence (NICE).
  • serum_Na - the measured concentration of sodium in the blood serum.
  • TBW - total body water. It's calculated 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 an 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 - the aimed serum sodium change per hour. As there is a risk of overcorrection
  • 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 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
Age/sex category
adult male
Serum sodium
Fluid sodium
0.9% NaCl (154 mmol/L)
Fluid potassium
Aimed serum sodium change per hour
Sodium change per liter
Correction rate
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