• Hyperglycaemic crises (DKA and HHS).
• Evaluating hyponatraemia in a diabetic patient to determine if it is "true" or "dilutional".
• Calculating free water deficit and total body cation requirements.

While 1.6 is the "traditional" factor, Hillier et al. demonstrated that a factor of 2.4 mg/dL is more accurate when serum glucose is significantly elevated (> 400 mg/dL).

As glucose levels fall during insulin therapy, the measured sodium will rise as water moves back into the cells. This is expected and desirable. A failure of measured sodium to rise while glucose is falling may indicate excessive free water administration and increased risk of cerebral oedema.