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Test Code CARFT Carbamazepine, Free and Total, Serum

Useful For

Monitoring carbamazepine (free and total) therapy in uremic patients

Profile Information

Test ID Reporting Name Available Separately Always Performed
CARTA Carbamazepine, Tot, S Yes Yes
CARF Carbamazepine, Free, S Yes Yes

Method Name

CARF: Ultrafiltration Followed by Homogeneous Microparticle Agglutination Immunoassay

CARTA: Homogeneous Microparticle Agglutination Immunoassay

Reporting Name

Carbamazepine, Free and Total, S

Specimen Type

Serum Red

Shipping Instructions


Specimen Required

Container/Tube: Red top

Specimen Volume: 2 mL

Collection Instructions: Tubes should be centrifuged and aliquoted within 2 hours of collection.

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Red Refrigerated (preferred) 7 days
  Frozen  28 days
  Ambient  48 hours

Reject Due To

Gross hemolysis Reject

Clinical Information

Carbamazepine (Tegretol) is an effective treatment for complex partial seizures, with or without generalization to tonic-clonic seizures. It is frequently administered in conjunction with other antiepileptic agents, such as phenytoin and valproic acid.


Under normal circumstances, the carbamazepine that circulates in blood is 75% protein bound. In severe uremia, carbamazepine may be displaced from protein, resulting in a higher free (unbound) fraction of the drug circulating in blood. Since neurologic activity and toxicity are directly related to the circulating free fraction of drug, adjustment of dosage based on knowledge of the free carbamazepine level may be useful in patients with severe uremia.

Reference Values


Therapeutic: 4.0-12.0 mcg/mL

Critical value: ≥15.0 mcg/mL



Therapeutic: 1.0-3.0 mcg/mL

Critical value: ≥4.0 mcg/mL

Day(s) and Time(s) Performed

Monday through Sunday; Continuously

Analytic Time

Same day/1 day

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

80156-Carbamazepine, Total, S

80157-Carbamazepine, Free, S

LOINC Code Information

Test ID Test Order Name Order LOINC Value
CARFT Carbamazepine, Free and Total, S 34545-4


Result ID Test Result Name Result LOINC Value
CARF Carbamazepine, Free, S 3433-0
CARTA Carbamazepine, Tot, S 3432-2

NY State Approved



If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.