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Calculator · Albumin-adjusted calcium
Corrected calcium
Roughly half of serum calcium is bound to albumin and is not physiologically active. A low albumin therefore makes the total look low when the free calcium is normal. Most UK labs report the corrected value already — this is for when it is not on the report…
Before you use it
The correction is an approximation and it fails where you most want it: critical illness, marked acid-base disturbance, and albumin below about 20 g/L. If the calcium actually matters — tetany, arrhythmia, an unexplained long QT — ask for an IONISED calcium on a blood gas rather than trusting the adjustment.
Source: Payne et al, BMJ 1973 / UK laboratory practice
Checked, and shown
Every threshold on this page was checked against its primary source by a practising doctor. Here is what that involved, and what it found.