Corrected Calcium Calculator

Correct serum calcium for low albumin levels in hypoalbuminemic patients.

Measured serum calcium (mg/dL) (mg/dL)

Normal: 8.5-10.5 mg/dL

Serum albumin (g/dL) (g/dL)

Normal: 4.0 g/dL

Ionized calcium (mmol/L, optional) (mmol/L)

Normal: 1.12-1.32 mmol/L; if available, use instead

Please check your inputs and try again.

Worked Examples

Example 1: Ca=8.0, Alb=2.5 (hypoalbuminemia)

Corrected = 8.0 + 0.8×(4-2.5)

Result: 9.2 mg/dL — actually normal!

Low albumin was masking true calcium level

Example 2: Ca=7.5, Alb=4.0 (normal albumin)

Corrected = 7.5 + 0

Result: 7.5 mg/dL — true hypocalcemia

No correction needed with normal albumin

Frequently Asked Questions

Why does albumin affect calcium measurement?

~40-45% of serum calcium is protein-bound (mostly to albumin). Low albumin means less bound calcium, so total calcium appears low even when ionized (active) calcium is normal.

When to use ionized calcium instead?

Critically ill patients, acid-base disturbances, after transfusions with citrated blood, and when accuracy is essential. Ionized calcium is the physiologically active form and doesn't need albumin correction.