Specimen Requirements


Calcium, Ionized

Specimen Requirement

Centrifuge and send unopened gel-barrier tube with vacuum intact. It is critical that the vacuum not be disrupted. Exposure of the serum to room air causes a loss of carbon dioxide to the atmosphere. This changes the sample pH and can prevent the lab from measuring the ionized calcium. To ensure that testing can be performed, SEND A SEPARATE TUBE FOR IONIZED CALCIUM and adhere a piece of labeling tape over the top of the tube with the following written on it “IONIZED CALCIUM-DO NOT OPEN.”


REJECTION CRITERIA: Hemolysis; opened gel-barrier tube; gel barrier not completely sealing the clot; plasma specimen; gross lipemia


Ion-selective electrode (ISE)


Room Temperature: 14 days, Refrigerated: 14 days; Frozen: Unacceptable

Reference Range

By Report*


1-3 days

Clinical Use

Evaluate nonbound calcium, calcium metabolism, physiologically active calcium fraction, hyperparathyroidism, ectopic hyperparathyroidism.

Test Code