Corrected Calcium Calculator

Adjust total serum calcium for low albumin to estimate the calcium that is physiologically active. Example: calcium 8.0 mg/dL with albumin 2.5 g/dL corrects to 9.2 mg/dL, which is normal.

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Units

Total calcium

Albumin

How to use the Corrected Calcium Calculator

Enter the values in the fields.
Press Calculate to see the result with the steps shown.

Formula and method

Corrected calcium (mg/dL) = measured calcium + 0.8 x (4.0 – albumin in g/dL). SI: corrected (mmol/L) = measured + 0.02 x (40 – albumin in g/L).

Normal calcium ranges

Measure	Conventional	SI
Total calcium	8.5 to 10.2 mg/dL	2.12 to 2.55 mmol/L
Albumin	3.5 to 5.0 g/dL	35 to 50 g/L
Ionized calcium	4.6 to 5.3 mg/dL	1.15 to 1.32 mmol/L

Why albumin matters

About 40% of blood calcium is bound to albumin. When albumin is low, total calcium reads low even if free calcium is normal, so the correction avoids over-treating.

Example corrections

Calcium	Albumin	Corrected
8.0	2.5	9.2
7.6	3.0	8.4
9.0	2.0	10.6
10.5	4.0	10.5

Limits

The correction can mislead in acidosis, alkalosis, kidney failure and critical illness. This calculator is for education and is not medical advice. Lab and clinical decisions belong with a qualified clinician who sees the whole picture.

Frequently asked questions

What is corrected calcium?

Total calcium adjusted for the albumin level.

What is the formula?

Calcium + 0.8 x (4 – albumin).

What is normal corrected calcium?

About 8.5 to 10.2 mg/dL.

When do I not need to correct?

When albumin is normal, or when ionized calcium is measured.

Is it accurate?

Only roughly; ionized calcium is better.

Can I use SI units?

Yes, choose SI.

Sources

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