Days Set Up
Daily, 24 hours
Analytic Time

2 hours

MiChart Code
Anti-Xa, (Enoxaparin, Lovenox) Low Molecular Weight Heparin
Soft Order Code

Test Updated:


Coagulation Factor Xa Inhibition
Factor Xa Inhibition
Heparin (LMWH) Anti-Xa Assay
Heparin, Low Molecular Weight
Low Molecular Weight Heparin
LMWH Anti-Xa
Anti-Xa, LMWH
Anti-Xa LMW Heparin
Chromogenic Xa
Xa Chromogenic
Factor 10a Inhibition
Anti-10a LMWH

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Test Overview

Test Methodology

Chromogenic Substrate Assay

Test Usage

Used to monitor treatment with low-molecular weight heparins: danaproid, enoxaparin, dalteparin, fragmin, lovenox

Reference Range

Normal individuals have no low molecular weight heparin activity.
Target Therapeutic Range:
Enoxaparin 1.0 mg/kg SC twice daily, 5 hours after dose 0.5 - 1.0 IU/mL;
Enoxaparin 1.5 mg/kg SC once per day, 5 hours after dose 1.0 - 2.0 IU/mL;
Enoxaparin 1.0 mg/kg SC once per day
Trough <0.4 IU/mL drawn just prior to next dose.
[bold]Critical value[/bold] is >2.0 IU/mL.

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

Specimen Requirements

Collection Offsite

Collect specimen in a blue top 3.2% sodium citrate Vacutainer® tube. Mix by inversion. Specimen should arrive at lab within 23 hours of collection; transport at room temperature. Alternatively, centrifuge, aliquot plasma into a plastic tube, and freeze the specimen within 24 hours of collection. Transport frozen specimen on dry ice. Collection of the blood through lines that have been previously flushed with heparin should be avoided. If the blood must be drawn through a VAD (vascular access device), the line should be flushed with 5 mL of saline and the first 5 mL of blood or six dead space volumes of the VAD discarded.

Blue Top Tube
Normal Volume
Full 2.7mL blue top 3.2% sodium citrate Vacutainer® tube or 1mL plasma aliquot
Minimum Volume
Full 1.8mL blue top 3.2% sodium citrate Vacutainer® tube or 1mL plasma aliquot

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.