In hypernatremia there is often a deficit of body water. From knowledge of body weight and serum sodium levels the magnitude of the deficit can be estimated.


Method 1


normal total body water in liters =

= 0.6 * (body weight in kilograms)


current total body water in liters =

= (normal serum sodium in mEq/L) * (normal total body water) / (measured serum sodium in mEq/L)


body water deficit =

= (normal total body water) - (current total body water)


Method 2


current total body water in liters =

= (factor) * (current body weight in kg)



• factor = 0.5 for males; 0.4 for females, the elderly in with cachexia


body water deficit in liters =

= (current total body water in liters) * (((serum sodium in mEq/L) / 140) - 1)


To read more or access our algorithms and calculators, please log in or register.