Carbamazepine, Free and Total, Serum or Plasma
Ordering Recommendation

Optimize drug therapy and monitor patient adherence.

Quantitative Enzyme Multiplied Immunoassay Technique
Mon, Thu
1-5 days
New York DOH Approval Status
This test is New York DOH approved.
Submit With Order
ARUP Consult®
Disease Topics
Specimen Required
Patient Preparation
Serum Pre-dose (Trough) Draw - At a Steady State Concentration in Plain Red. 
Specimen Preparation
Separate from cells ASAP or within 2 hours of collection. Transfer 2 mL serum to an ARUP Standard Transport Tube. (Min: 1 mL) 
Storage/Transport Temperature
Unacceptable Conditions
Whole Blood, Citrated Plasma. Tubes that contain liquid anticoagulant.or Serum separator tube (SST). 
Ambient: 5 days; Refrigerated: 5 days; Frozen: 3 months 
Reference Interval
Effective November 16, 2015
Test Number
Reference Interval
 Total CarbamazepineTherapeutic Range: 4.0-12.0 µg/mL
Toxic Range: Greater than 15 µg/mL
 Free CarbamazepineTherapeutic Range: 1.0-3.0 µg/mL
Toxic Range: Greater than 3.8 µg/mL
 Percent Free Carbamazepine8.0-35.0%

Interpretive Data
The therapeutic range is based on serum pre-dose (trough) draw at steady-state concentration. Free carbamazepine may be important to monitor in patients with altered or unpredictable protein binding capacity. Carbamazepine is also subject to drug-drug interactions due to displacement of protein binding and extensive metabolism. Cross-reactivity with metabolites may account for differences in carbamazepine among analytical methods. Calculating percent free attempts to minimize differences in assay cross-reactivity and may be useful in dose optimization.

A rare adverse drug reaction to carbamazepine therapy includes Stevens-Johnson syndrome or toxic epidermal necrolysis. Patients of Asian ancestry with the presence of the HLA-B*15:02 have an increased risk for this carbamazepine-induced life-threatening reaction. Pharmacogenetic testing for HLA-B*15:02 is recommended for patients at risk for carbamazepine hypersensitivity prior to treatment. This information has been included in the FDA-approved label for carbamazepine ( and guideline from the Clinical Pharmacogenetics Implementation Consortium ( [ARUP test code 2012049, HLA-B*15:02 Genotyping, Carbamazepine Hypersensitivity.] A combination of therapeutic drug monitoring with HLA-B*15:02 pharmacogenetics genotyping may benefit patients who are at increased risk for developing carbamazepine-induced adverse events due to rare genotypes other than HLA-B*15:02 variant allele.

Hotline History
View Hotline History
Component Test Code*Component Chart NameLOINC
2011768Free Carbamazepine3433-0
2011769Percent Free Carbamazepine32852-6
2011770Total Carbamazepine3432-2
* 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.
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