Heparin Anticoagulant Therapy and Its Monitoring.

Heparin remains a foundational parenteral anticoagulant across both acute and chronic care settings. This narrative review summarizes clinical indications and dosing of unfractionated (UFH) and low-molecular-weight heparin (LMWH). It also details laboratory monitoring using activated partial thromboplastin (APTT), anti-factor Xa (anti-Xa), activated clotting time (ACT) and viscoelastic testing (VET), including common pitfalls and interferences. We provide considerations for specific populations as well as complications including heparin resistance, heparin-induced thrombocytopenia (HIT) and heparin reversal strategies. Future research directions include harmonization of therapeutic ranges, mitigation of assay interference and prospective evaluation on monitoring, particular in extracorporeal membrane oxygenation (ECMO), pregnancy and cardiac surgical settings.