Calcium, Ionized

Test Code

CPT Codes

Preferred Specimen
2 mL serum collected in a gel barrier tube

Minimum Volume
0.6 mL

Other Acceptable Specimens
SST (red/black-top) tube


Let clot and spin immediately with the cap on. Do not open tube. Ship the unopened gel barrier tube at room temperature.
If submitting with any other assay, please submit a separate tube for this test.

Transport Container
Unopened gel barrier tube

Transport Temperature
Room temperature

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

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Gross hemolysis • Grossly lipemic • Received frozen • Red-top tube (no gel)

Ion Specific Electrode (ISE)

Setup Schedule

Report Available
1-3 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-Lenexa
10101 Renner Blvd
Lenexa , KS 66219-9752

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.