LMWH remains useful when oral anticoagulants are difficult to use safely in venous thromboembolism patients

BackgroundDespite 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.MethodsWe 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.ResultsLMWH 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.ConclusionLMWH 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.