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Adds 0.8 mg/dL of calcium for every 1 g/dL that albumin falls below 4 g/dL, the standard correction for protein-bound calcium.
Calcium correction
Corrected Ca (mg/dL) = measured Ca + 0.8 x (4.0 - albumin g/dL); divide by 4.008 for mmol/L
Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
Roughly 40% of calcium is albumin-bound, so low albumin lowers total calcium without changing the ionised fraction.
Yes, a direct ionised calcium measurement is preferred when available, particularly in critical illness.