Calcium Correction for Hypoalbuminemia and Hyperalbuminemia

Why Use

Correcting serum calcium levels for levels of albumin outside of the normal range will allow clinicians to: Identify patients whose ionized calcium levels may be out of normal range despite total calcium levels appearing to be within normal range. Identify patients whose ionized calcium levels are likely in normal range while their total calcium levels appear abnormal.

When to Use

Patients with albumin below the laboratory value of lower limit of normal. Patients with albumin above the laboratory value of upper limit of normal.

Formula

Pearls / Pitfalls

The total amount of calcium in the serum is found bound to albumin and multiple organic and inorganic anions, while some circulates as ionized or free calcium. Changes in albumin can result in a decrease in total calcium (pseudohypocalcemia) or increase in total calcium (pseudohypercalcemia), without changing ionized calcium. Rarely, changes in gamma globulins (in multiple myeloma) can result in pseudohypercalcemia. Finally, an increase in extracellular pH can result in changes in ionized calcium without changing total calcium.

Management

If calcium is confirmed to be outside of normal range, consider a diagnostic evaluation to determine the etiology. Common causes of Hypocalcemia: Vitamin D inadequacy or resistance. Hypoparathyroidism. Renal disease or end-stage liver disease causing vitamin D inadequacy. Malabsorption. Post-gastric bypass surgery. Drugs and toxic ingestions. Hypomagnesemia. Common Causes of Hypercalcemia: Primary hyperparathyroidism. Vitamin D toxicity. Vitamin A toxicity. Cancer. Sarcoidosis. Medications (e.g. lithium and thiazide diuretics). Dehydration or volume depletion. Genetic conditions (e.g. familial hypocalciuric hypercalcemia). Little or no movement.

Advice

Consider measuring ionized calcium to confirm conclusions drawn after correcting for serum calcium.