Serum total calcium must be corrected for albumin because approximately 40% of calcium is protein-bound. Low albumin causes total calcium to underestimate the physiologically active fraction.
Corrected Calcium Calculator
How to Use the Corrected Calcium Calculator
This corrected calcium calculator applies the standard formula: Corrected Ca = Total Ca + 0.8 × (4.0 − Albumin). It is most useful when hypoalbuminemia is suspected or confirmed.
Clinical Example
A patient has measured calcium of 7.8 mg/dL (appears low) with albumin of 2.0 g/dL. Corrected Ca = 7.8 + 0.8 × (4.0 − 2.0) = 7.8 + 1.6 = 9.4 mg/dL — actually normal. Without correction, this patient might be incorrectly treated for hypocalcemia.
FAQ
Is this corrected calcium calculator free?
Yes, completely free with no signup required.
What is the corrected calcium formula?
Corrected Ca = Total Ca + 0.8 × (4.0 − Albumin). For every 1 g/dL decrease in albumin below 4.0, add 0.8 mg/dL to the measured calcium. This accounts for the fact that about 40% of calcium is protein-bound, primarily to albumin.
When should calcium be corrected for albumin?
Correct calcium whenever albumin is below 3.5 g/dL. Critically ill patients, malnourished patients, and those with liver disease frequently have low albumin, causing measured total calcium to underestimate the biologically active calcium. Ionized calcium measurement is more accurate when available.
What is a normal serum calcium?
Normal serum calcium is approximately 8.5–10.5 mg/dL (2.12–2.62 mmol/L). Below 8.5 mg/dL is hypocalcemia; above 10.5 mg/dL is hypercalcemia. These cutoffs apply to corrected calcium values.