Calcium Albumin Correction — Clinical Calculator & Interpretation
Calculate albumin-corrected calcium with step-by-step interpretation. Understand hypocalcemia vs. pseudo-hypocalcemia in hypoalbuminemic patients. Free calculator.
Understanding Pseudo-Hypocalcemia
Pseudo-hypocalcemia occurs when total serum calcium appears low due to low albumin, but ionized calcium — the biologically active fraction — is normal. This is a common finding in hospitalized patients, up to 40% of whom have some degree of hypoalbuminemia.
| Condition | Total Ca | Albumin | Corrected Ca | Ionized Ca |
|---|---|---|---|---|
| True hypocalcemia | Low | Normal | Low | Low |
| Pseudo-hypocalcemia | Low | Low | Normal | Normal |
| Normal | Normal | Normal | Normal | Normal |
| True hypercalcemia + low albumin | Normal/Low | Low | High | High |
Clinical Causes of Low Albumin Requiring Correction
Common causes of hypoalbuminemia in clinical practice include: liver cirrhosis (reduced synthesis), nephrotic syndrome (urinary protein loss), protein-calorie malnutrition, inflammatory states (albumin as negative acute phase reactant), burns, and post-surgical fluid resuscitation with dilution. The calcium-albumin correction should be performed routinely whenever albumin falls below 4.0 g/dL.
Frequently Asked Questions
What albumin level requires calcium correction?
Calcium correction should be applied whenever albumin falls below 4.0 g/dL (40 g/L in SI units), which is the reference point in the standard Payne correction formula. The lower the albumin, the larger the correction and the greater the difference from the measured value.
Is the albumin-corrected calcium formula accurate in all patients?
No. The Payne formula is least accurate in critically ill patients, those with acid-base disturbances, very low albumin (<2 g/dL), and patients with abnormal globulin levels. Direct measurement of ionized calcium (Ca²⁺) using a blood gas analyzer is the gold standard in these cases.