Skip to main content

Anti Xa heparin assay

Alias: Anti-Xa, Xa inhibition, Anti-factor Xa heparin, Heparin level

Discipline: Coagulation

Test information: To monitor low molecular weight heparin (LWMH) therapy and sometimes to monitor unfractionated heparin (UFH) therapy.
The test is also used to measure Edoxaban, Rivaroxaban and Apixaban.

Specimen Type(s)
  • Blood;
Other Acceptable Specimen Type(s)
Specimen Container - Adult
  • Light Blue Top BD;
Specimen Container - Paediatric
  • N/A;
  • N/A;
Part of a test profile?
Volume (min) of sample to be sent to laboratory
Patient Preparation, Sample Handling and Transport
Anti-Xa is primarily requested as a "peak" test.
It is collected about 3-4 hours after a LMWH dose is given, when the concentration of LMWH in the blood is expected to be at its highest level.
Random and "trough" anti-Xa tests may also be requested when a doctor suspects that a patient may not be clearing the LMWH at a normal rate.
Trough tests are collected just prior to the next dose, when heparin concentrations are expected to be at their lowest.
Samples should be taken at Peak response time, for LMWH = 4 hours post last dose and Rivaroxaban & Apixaban = 3 hours post last dose and Edoxaban = 2 hours post dose.
Please make a note of any anticoagulants and/or bleeding/bruising symptoms.
Maximum add on time
4 hours
Units and Reference Ranges / Interpretation
0 - 0.35 iu/ml for LMWH 457 ng/ml for Rivaroxaban 0-508 ng/ml for Apixaban 80-500ng/ml for Edoxaban
UKAS number
UKAS accredited test?
Testing is available outside normal laboratory hours.

If you have any queries about a test or results interpretation please contact us.

Last updated: 03-05-2024