Revisiting low-molecular-weight heparin for venous thromboembolism: from pharmacology to precision dosing and implementation.

Background: Despite the increasing use of direct oral anticoagulants, low-molecular-weight heparin (LMWH) remains important in venous thromboembolism (VTE) care when oral therapy is unsuitable, temporarily unsafe, or difficult to manage, particularly during pregnancy, cancer-associated thrombosis, renal impairment, and peri-procedural care. Objective: To review how LMWH pharmacology informs practical decisions about dosing, anti-factor Xa monitoring, treatment interruption and restart, and switching between anticoagulants. Methods: We performed a narrative review of contemporary guidelines, randomized trials, systematic reviews, pharmacokinetic/pharmacodynamic studies, drug labels, and laboratory medicine evidence, focusing on literature published from 1 January 2015 to 18 December 2025, with selected earlier sources retained for foundational pharmacologic principles. Results: LMWH can be used with standard fixed or weight-based dosing in many stable patients, but reassessment is needed when renal function, body weight, pregnancy physiology, cancer-related bleeding risk, critical illness, or procedural timing changes the relationship between dose and exposure. Anti-factor Xa testing should not be used routinely; it is most useful when sampling is standardized and the result can guide a specific action, such as dose adjustment, interval extension, treatment interruption, or switching to unfractionated heparin. Conclusion: LMWH remains useful when oral anticoagulants are difficult to use safely. Its clinical value depends on clear dose selection, renal-function reassessment, selective monitoring, planned interruption and restart, and timely switching when patient risk or treatment feasibility changes.