Sodium Correction
for Hyperglycaemia

Sodium Correction — Clinical Guide

Why Correct Sodium for Glucose?

Hyperglycaemia creates an osmotic gradient that draws water from the intracellular to extracellular space, diluting serum sodium by approximately 1.6–2.4 mmol/L for every 100 mg/dL (5.6 mmol/L) rise in glucose above 100 mg/dL. The measured sodium is therefore artifactually low. The corrected sodium reflects what the sodium would be at a normal glucose level — this is the clinically important value for managing fluid replacement.

Clinical Implications in DKA and HHS

• DKA: Corrected Na helps assess true hydration status. In DKA, corrected Na >135 indicates hypernatraemia that will be unmasked as glucose falls with treatment — use more hypotonic fluid (0.45% NaCl after initial resuscitation)
• HHS: Corrected Na often markedly elevated in HHS (corrected Na >145 is common). Guides initial fluid choice — normal saline first to restore volume, then switch to 0.45% NaCl to correct free water deficit
• Hillier formula (2.4): Preferred for glucose >400 mg/dL — more accurate at very high glucose levels. Katz (1.6) traditionally taught but underestimates correction at extreme hyperglycaemia

Which Formula to Use?

Use Hillier (2.4) for glucose >400 mg/dL (22 mmol/L) — this is now preferred in most guidelines. Use Katz (1.6) for moderate hyperglycaemia (180–400 mg/dL). Both formulas are presented in the result — the Hillier corrected Na is often the clinically more relevant value in severe hyperglycaemia such as HHS.

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