If total calcium is 8.0 mg/dL and albumin is 2.0 g/dL, the corrected calcium is approximately?

If total calcium is 8.0 mg/dL and albumin is 2.0 g/dL, the corrected calcium is approximately?

• A. 8.0 mg/dL
• B. 9.0 mg/dL
• C. 9.6 mg/dL
• D. 10.4 mg/dL

Answer: (C)

Calcium correction accounts for how albumin binds calcium. Since most calcium is bound to albumin, a low albumin level makes the total calcium look low even if the active portion isn’t actually deficient. The correction uses the formula: corrected calcium = measured total calcium + 0.8 × (4 − albumin in g/dL). Here, albumin is 2.0 g/dL, so 4 − 2 = 2.0; 0.8 × 2.0 = 1.6. Add this to the measured total calcium: 8.0 + 1.6 = 9.6 mg/dL. So the corrected calcium is about 9.6 mg/dL. This helps indicate the true calcium status when albumin is low.

Calcium correction accounts for how albumin binds calcium. Since most calcium is bound to albumin, a low albumin level makes the total calcium look low even if the active portion isn’t actually deficient. The correction uses the formula: corrected calcium = measured total calcium + 0.8 × (4 − albumin in g/dL). Here, albumin is 2.0 g/dL, so 4 − 2 = 2.0; 0.8 × 2.0 = 1.6. Add this to the measured total calcium: 8.0 + 1.6 = 9.6 mg/dL. So the corrected calcium is about 9.6 mg/dL. This helps indicate the true calcium status when albumin is low.