Corrected Sodium

Hyperglycaemia draws water into the vascular space and dilutes sodium, so the measured value understates true sodium. Correcting matters because a “normal” sodium in marked hyperglycaemia may represent significant hypernatraemia once glucose falls. Both factors are shown because the literature disagrees — Katz’s 1.6 is the classic derivation, Hillier’s 2.4 fits observed data better at glucose above ~22 mmol/L. Use the corrected value to guide fluid choice and to anticipate the sodium rise as glucose is treated, not as a target in itself.