Albumin-Corrected Calcium
Provide total serum calcium, albumin, and measurement units to calculate corrected calcium. Use the result to screen for hypo- or hypercalcaemia when ionized calcium is unavailable.
Use total calcium concentration reported by the laboratory.
Normal albumin is ~4.0 g/dL. Lower albumin reduces measured calcium.
Corrected calcium
9.40 mg/dL
Corrected calcium (SI)
2.35 mmol/L
Corrected calcium within reference range
How to Use This Calculator
Obtain total calcium and albumin
Use the same blood draw for both measurements whenever possible to avoid time-dependent changes.
Select correct units
Choose mg/dL or mmol/L depending on laboratory reporting. The result is displayed in both units.
Interpret within clinical context
Corrected calcium is a screening tool. Confirm abnormal results with ionized calcium levels, especially in critical illness.
Formula
Corrected Ca (mg/dL) = Measured Ca + 0.8 * (4 - Albumin)
Corrected Ca (mmol/L) = Corrected Ca (mg/dL) / 4
Albumin in g/dL; assume normal albumin 4 g/dL. For SI units (albumin g/L) adjust coefficient accordingly.
Full Description
Total serum calcium binds to albumin; hypoalbuminemia lowers measured calcium despite normal ionized levels. The corrected calcium formula compensates for this effect, improving screening for true calcium disorders. However, in critically ill patients or those with acid-base abnormalities, direct ionized calcium measurement is more reliable. Use corrected calcium to guide initial evaluation, then confirm with definitive testing if clinically indicated.
Frequently Asked Questions
Is the correction accurate in critical illness?
No. Acid-base changes, renal failure, or sepsis alter calcium binding. Measure ionized calcium when accuracy is crucial.
What if albumin is reported in g/L?
Convert to g/dL by dividing by 10, or adjust the coefficient (0.02 instead of 0.8) for calculations in SI units.
Should I correct in hyperalbuminemia?
Yes. The formula adjusts in both directions. Elevated albumin will decrease corrected calcium, aligning with ionized levels.
When should I order ionized calcium?
Obtain ionized calcium in critically ill patients, those with unexplained symptoms, or when corrected calcium conflicts with clinical findings.