Calcium, Ionized [306]

For Specimen Integrity during Extreme Weather see the “Lockbox Usage in Extreme Weather” document at the top of this page.

Test Code

Alias/See Also
Calcium Free;
Free CA;
Free Calcium;
Ionized Calcium

CPT Codes

Preferred Specimen
2 mL serum collected in a serum separator tube (SST)

Minimum Volume
0.6 mL

Collect blood (2 mL serum) in a gel barrier tube. Let clot and spin immediately with cap on. Do not open tube. Ship the unopened gel barrier tube at room temperature. Do not freeze.
If submitting with any other assay. Please submit a separate tube for this test.

Transport Temperature
Room temperature

Specimen Stability
Room temperature: 7 days
Refrigerated: 7 days
Frozen: Unacceptable

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Received frozen; gross hemolysis; grossly lipemic; Red-top tube (no gel)

Ion Specific Electrode (ISE)

Setup Schedule
Set up: Daily; Report available: 1-2 days

Reference Range
<8 Months 5.3-6.3 mg/dL
8-11 Months5.2-6.1 mg/dL
1 Year5.1-6.0 mg/dL
2 Years4.9-5.8 mg/dL
3 Years4.9-5.7 mg/dL
4-6 Years4.8-5.7 mg/dL
7-12 Years4.8-5.6 mg/dL
13-17 Years4.8-5.5 mg/dL
18-89 Years4.7-5.5 mg/dL
≥90 Years4.5-5.5 mg/dL

Clinical Significance
Ionized calcium represents the true "bioavailable" calcium in the circulation. In situations where the total calcium is normal but does not fit the clinical picture, e.g. , hyperparathyroidism, a determination of the ionized calcium will, many times, show an elevation in the "bioavailable" calcium component. This may be due to alterations in protein concentrations, especially albumin, that binds most of the calcium in the circulation.

Performing Laboratory
Quest Diagnostics Nichols Institute
14225 Newbrook Drive
Chantilly, VA 20153

Last Updated: November 24, 2021

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.