Lab Test

Calcium, Ionized

Ionized Calcium

Test Codes

EPIC: LAB5342, Beaker: CAION, Antrim: 15641




Ionized Calcium is to be drawn before any tubes, including routine or fungal/AFB blood cultures.

Specimen Collection Criteria

Preferred Sample Type:  
One 5.0 mL completely filled Gold-top SST tube (adults) or one 0.3 mL completely filled SST Microtainer® (neonatal or pediatric ONLY). Minimum Whole Blood: 5.0 mL (Gold-top SST) or 0.3 mL (SST Microtainer®).*

*Venous or arterial blood is required for adults. If heel-stick is necessary in neonates or fingerstick in pediatrics, minimize exposure of the sample to air during collection.

Acceptable Sample Type: One blood gas syringe (see Blood Gas Procedure below).** 

See Minimum Pediatric Specimen Requirements.

**NOTE: Blood Gas syringe specimens should ONLY be collected at the Dearborn, Farmington Hills, Grosse Pointe, Royal Oak, Taylor, Trenton, Troy, or Wayne Hospital Campuses. Specimens should NOT be collected at any other Beaumont Laboratory draw-site, Nursing Home, or Outreach office. 

Collection Procedure for Blood Gas Syringes ONLY: 

  • A 1 mL or 3 mL plastic syringe containing dry heparin is usually used to collect the specimen.
  • At least 1-2 mL (0.3 mL for pediatric patients) of blood is needed to ensure proper assay.
  • Arterial specimens are collected by a physician, nurse, or respiratory therapist.
  • For specimens collected by syringe, any air bubbles present in the syringe must be immediately expelled, the needle removed, and the syringe tightly capped. The syringe is rolled between the palms of the hands to ensure mixing.
    • Note: The Radiometer safePICO self-fillTM syringe has a metal ball to ensure homogeneous mixing when the syringe is rolled between the palms of the hands.
  • Characterization of oxygen enrichment, at the time of arterial puncture, is required. This may be expressed as FiO2 fractional inspired oxygen concentration provided (e.g. 0.50), FiO2% (e.g. 50%), room air, or nasal cannula flow rate in liters per minute. The FiO2 must be noted on the requisition or entered as part of the electronic order for any arterial blood gas specimens.
  • The specimen must be properly labeled.
  • Place on wet ice for transport. Ice and Specimen must be kept separated.
    • Suggested: Place specimen in front pocket of the biohazard bag. Place ice in zip lock section of biohazard bag.
  • The specimen must be transported immediately to the STAT Laboratory (Royal Oak) or to the Chemistry Laboratories. 

Physician Office/Draw Specimen Preparation

SST tubes or Microtainers® only.

DO NOT remove Vacutainer® stopper. Let SST specimens clot 30-60 minutes then immediately centrifuge to separate serum from cells. Specimens must be centrifuged within one hour of collection. Refrigerate (2-8°C or 36-46°F) the centrifuged SST tube within four hours of collection.

Preparation for Courier Transport

Transport: Centrifuged SST tube, refrigerated (2-8°C or 36-46°F).

Rejection Criteria

  • Moderate to severely hemolyzed specimens.
  • Specimens not collected and processed as indicated.
  • Specimens collected in a Green-top (Heparin) Vacutainer® tube.
  • Specimens will not be tested if the Vacutainer® stopper has been previously removed.

Inpatient Specimen Preparation

  • Transport SST tubes or Microtainers® to the Laboratory immediately.
  • If a blood gas specimen was collected, transport STAT, on wet ice, to the STAT Laboratory (Royal Oak) or the Chemistry Laboratories. 

In-Lab Processing

SST tubes and Microtainers®DO NOT remove Vacutainer® stopper. Let SST specimens clot 30-60 minutes then immediately centrifuge to separate serum from cells. Specimens must be centrifuged within one hour of collection. Deliver immediately to the appropriate testing station.

Blood Gas specimens: Immediately analyze the whole blood, heparinized, iced specimen upon receipt.


Specimen Stability for Testing:

Centrifuged SST Tubes and Microtainers® with Separator Gels
Room Temperature (20-26°C or 68-78.8°F): 4 hours
Refrigerated (2-8°C or 36-46°F): 48 hours
Frozen (-20°C/-4°F or below): Unacceptable

Blood Gas Syringes

Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): 1 hour
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

SST Tubes and Microtainers®: Refrigerated (2-8°C or 36-46°F) for 7 days.

Blood Gases: Specimens are disposed within 8 hours of testing.


Dearborn Chemistry Laboratory
Farmington Hills Chemistry Laboratory 
Grosse Pointe Chemistry Laboratory 
Livonia Main Laboratory
Lenox Main Laboratory
Royal Oak STAT Laboratory 
Troy Chemistry Laboratory
Taylor Chemistry Laboratory
Trenton Chemistry Laboratory
Wayne Chemistry Laboratory 


Sunday – Saturday, 24 hours a day.
Routine results available within 4 hours.

STAT results available within 1 hour after receipt in the STAT Laboratory (Royal Oak) or Chemistry Laboratories. 

Reference Range

Age related reference range:

Age Range (mg/dL)
0 – 1 day 4.20 – 5.48
2 – 3 days 4.40 – 5.68
4 – 5 days 4.80 – 5.92
6 days – adult 4.48 – 5.28

Test Methodology



Ionized calcium represents the free or physiologically active component of serum/plasma calcium. It frequently parallels the total calcium level. However, in plasma protein or acid-base abnormalities the ionized calcium often provides more useful information on calcium status than does total calcium. An increase in blood pH is associated with a decrease in ionized calcium; a decreased blood pH is associated with an increased ionized calcium. Patients with low calcium and low albumin frequently have normal ionized calcium levels. See total calcium for causes of hyper and hypocalcemia.

Low ionized calcium values may be seen in patients receiving rapid transfusion of citrated whole blood or blood products.

Clinical Utility

Ionized calcium is useful for the assessment of calcium status in patients with acid-base or plasma protein abnormalities and those in whom the total calcium result does not correlate with clinical finding. The ionized calcium assay provides useful information during liver transplantation surgery, cardiopulmonary bypass, or any procedure requiring rapid transfusion of whole blood.

CPT Codes

LOINC: 17864-0


Last Updated


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