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Anti-Xa Level

Anti-Factor Xa Anti-Xa Activity Heparin Level
Sodium citrate (blue top; timed post-dose) IU/mL

About this test

Functional assay measuring inhibition of factor Xa, used to monitor low-molecular-weight heparin (LMWH) and fondaparinux therapy. Target levels depend on agent, dose, and indication.

Reference Ranges

Sex Age Range Notes
All ≥ 18 yrs See notes LMWH prophylaxis (4h post-dose): 0.2–0.4; treatment (4h peak): 0.5–1.0; trough <0.2

Clinical Interpretation

Low / Decreased
Subtherapeutic — insufficient anticoagulation; thrombosis risk.
High / Increased
Supratherapeutic — increased bleeding risk. Renal failure impairs LMWH clearance.

Related Tests

Creatinine
Specimen
Sodium citrate (blue top; timed post-dose)
Reporting Unit
IU/mL
Category
🩹 Coagulation

⚠ Clinical Note
Reference ranges are indicative. Always interpret results in the context of the individual patient and local laboratory reference intervals, which may vary.