Corrected Calcium Calculator
Corrected Calcium
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Interpretation
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Correcting Calcium for Albumin
~40% of serum calcium is albumin-bound. Low albumin makes total calcium appear falsely low. Corrected Ca = Total Ca + 0.8*(4.0-albumin).
Normal calcium: 8.5-10.5 mg/dL. For every 1 g/dL albumin drop below 4.0, total calcium drops ~0.8 mg/dL.
Limitations: less reliable in critically ill, renal failure, acid-base disturbances. Ionized calcium preferred when available.
Frequently Asked Questions
Correction formula?
Corrected Ca = Measured Ca + 0.8*(4.0-Albumin). Both in standard units (mg/dL and g/dL).
Why correct for albumin?
Low albumin artificially lowers total calcium. Patient with albumin 2.0, Ca 7.5 actually has corrected 9.1 (normal).
When unreliable?
Critically ill, kidney failure, acid-base abnormalities, albumin very low (<2.0). Use ionized calcium.
Normal ionized calcium?
4.5-5.3 mg/dL. Active fraction unaffected by albumin.