Calcium, Ionized, Serum
Ordering Recommendation

Assess calcium status.

Ion-Selective Electrode/pH Electrode
Within 24 hours
New York DOH Approval Status
This test is New York DOH approved.
Submit With Order
ARUP Consult®
Disease Topics
Specimen Required
Patient Preparation
Serum separator tube. 
Specimen Preparation
Do not open the tube or split the specimen. Do not freeze separator tube. Do not expose specimen to air at any time during collection or transport process.  Centrifuge with stopper in place within one hour of collection. Transport 5 mL serum in original serum separator tube. (Min: 0.5 mL) 
Storage/Transport Temperature
Refrigerated. Ship upright in original serum separator collection tube  and transport in the ARUP shipping rack. Do not ship on dry ice. 
Unacceptable Conditions
Ambient: 24 hours; Refrigerated: 1 week; Frozen: Unacceptable 
Reference Interval
Ionized calcium (ISE):
Birth up to 1 month: 1.10-1.35 mmol/L
1 month-adult: 1.11-1.30 mmol/L

Ionized calcium (calculation at pH 7.4):
Birth up to 1 month: 1.10-1.35 mmol/L
1 month-adult: 1.11-1.30 mmol/L
Interpretive Data

Differences between the ionized calcium result and the ionized calcium normalized to pH 7.4 are due to the sample having a pH significantly different from pH 7.4.  Specimen pH may be artificially decreased due to delayed processing and may be increased when the specimen is exposed to air.  Due to these factors, it is recommended that the ionized calcium normalized to pH 7.4 be interpreted with caution and only used when the clinician has knowledge of the patient's acid/base status.  Accurate determination of in vivo pH is best determined by arterial blood gas testing.
Hotline History
Component Test Code*Component Chart NameLOINC
0020136Calcium, Ionized Serum12180-6
0020138Calcium Ionized pH 7.419072-8
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
  • CA Ionized, Serum
  • Free Calcium
  • Ionized Calcium