Enter the urinary sodium concentration and urine volume into the calculator to determine the sodium loss.

Sodium Loss Formula

The following formula is used to calculate the sodium loss.

SL = (U * V) / W


  • SL is the sodium loss (mmol) U is the urinary sodium concentration (mmol/L) V is the urine volume (L) W is the body weight (kg)

To calculate the sodium loss, multiply the urinary sodium concentration by the urine volume. Then divide the result by the body weight.

What is a Sodium Loss?

Sodium loss refers to the condition where the body loses more sodium than it takes in. Sodium is a crucial electrolyte that helps regulate water levels in the body’s cells and aids in various bodily functions such as maintaining blood pressure and supporting nerve and muscle function. Sodium loss can occur due to excessive sweating, chronic diseases like kidney disease, certain medications, or inadequate sodium intake. This can lead to a condition called hyponatremia, characterized by low sodium levels in the blood, which can cause symptoms like headache, nausea, fatigue, confusion, seizures, and in severe cases, coma or death.

How to Calculate Sodium Loss?

The following steps outline how to calculate the Sodium Loss (SL).

  1. First, determine the urinary sodium concentration (U) in mmol/L.
  2. Next, determine the urine volume (V) in L.
  3. Next, gather the formula from above = SL = (U * V) / W.
  4. Finally, calculate the Sodium Loss (SL) in mmol.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

urinary sodium concentration (U) = 10 mmol/L

urine volume (V) = 2 L

body weight (W) = 70 kg