Why correct calcium for albumin?

~40% of serum calcium is bound to albumin. Low albumin causes falsely low total calcium. Correction estimates what the calcium would be at normal albumin (4 g/dL).

What is the correction formula?

Corrected Ca = Measured Ca + 0.8 × (4 - Albumin). For each 1 g/dL decrease in albumin below 4, add 0.8 mg/dL to the measured calcium.

When should I use ionized calcium instead?

Ionized calcium is preferred in critically ill patients, those with acid-base disturbances, or when albumin correction may be inaccurate. It directly measures biologically active calcium.

What is normal corrected calcium?

Normal: 8.5-10.5 mg/dL. Hypocalcemia: 10.5 mg/dL. Critical values require urgent attention.

Does the formula work for high albumin?

The formula is most validated for hypoalbuminemia. With high albumin (>4), it may overcorrect. Consider ionized calcium if albumin is significantly elevated.

What causes pseudohypocalcemia?

Low albumin (malnutrition, liver disease, nephrotic syndrome) causes low total calcium with normal ionized calcium. The corrected calcium formula accounts for this.

Corrected Calcium Calculator

Adjust calcium level for hypoalbuminemia.

Lab Values

Serum Calcium

mg/dL

Total serum calcium. Normal: 8.5-10.5 mg/dL. May be falsely low with hypoalbuminemia.

Serum Albumin

g/dL

Serum albumin level. Normal: 3.5-5.0 g/dL. Low albumin causes falsely low total calcium.

Corrected Calcium

0.0 mg/dL

Severe Hypocalcemia

Measured Ca

8 mg/dL

Albumin

3 g/dL

Correction Factor

+0.80 mg/dL

Corrected Ca

0.0 mg/dL

Formula

Corrected Ca = Measured Ca + 0.8 × (4 - Albumin)

= 8 + 0.8 × (4 - 3) = 8 + 0.80 = 0.0 mg/dL

For each 1 g/dL decrease in albumin below 4, add 0.8 mg/dL to calcium.

Frequently Asked Questions

How to Use

About the Corrected Calcium Calculator

What it calculates

This corrected calcium calculator applies a validated clinical scoring method used in healthcare settings. Calcium correction for albumin.

When to use it

Use as a clinical decision support aid alongside professional judgment — not as a standalone diagnosis.

Example

Adjust the inputs above to model your specific scenario with the Corrected Calcium Calculator.

Explore More

Corrected Calcium Calculator

Lab Values

0.0 mg/dL

Severe Hypocalcemia

Formula

About the Corrected Calcium Calculator

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