Days Set Up
Analytic Time

5 - 7 days

Soft Order Code

Test Updated:



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Find a Requisition

All specimens should be accompanied by a requisition.

Submitting Specimens

Learn about how to properly label and where to ship specimens.

Order Kits and Supplies

MLabs provides all the supplies necessary for the collection of specimens.

Test FAQ

Visit our provider FAQ and learn about common questions to ordering tests.

Test Overview

Test Methodology

Gas Chromatography/Flame Ionization Detection (GC-FID)

Test Usage

Therapeutic drug monitoring.

Reference Range

5 - 20 mcg/mL. Critical Value: 35 mcg/mL.

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Specimen Requirements

Collection Onsite

Collect blood in red or green top tube; do not use SST tube.

Collection Offsite

Collect blood in red or green top tube; do not use SST tube. Centrifuge, aliquot serum or plasma into a plastic vial and refrigerate or freeze.

Yellow Top Tube
Red Top Tube
Normal Volume
2 mL serum or heparinized plasma
Minimum Volume
0.3 mL serum or heparinized plasma

Billing Information

CPT Code
Pro Fee Code

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Our High Standard

Quality that sets us apart

As the reference laboratory division of Michigan Medicine's Department of Pathology, MLabs shares the institution's commitment to applying established quality principles to clinical laboratory testing. Like other large organizations in complex, consequential fields, we rely on an established approach to monitor quality throughout the testing process.