Unfractionated heparin (UFH) remains the anticoagulant of choice in critically ill patients. However, its laboratory monitoring and clinical management are particularly challenging. Between November 2023 and February 2024, we surveyed 142 clinicians and laboratory medicine specialists from 15 countries involved in the care of patients receiving therapeutic-intensity UFH. Our objective was to describe current practices and variations among centers. UFH monitoring was based on an anti-Xa assay or on activated partial thromboplastin time in 54% and 46% of respondents, respectively. Different therapeutic ranges were used depending on local protocols and indications; the 0.3-0.7 IU/mL anti-Xa range was commonly used, except for patients on mechanical circulatory support with a lower range, mostly 0.3-0.5 IU/mL. Most respondents managed therapeutic UFH administration with weight-based dosing (88%), while fewer used a nomogram (57%) for dose adjustment. When a nomogram was used, it was primarily based on anti-Xa monitoring (86%). The situations when respondents administered antithrombin varied widely; 22% reported using it when antithrombin levels were below 60IU/dL(%) and 20% reported never using it. Our survey results revealed considerable heterogeneity in UFH management approaches, reflecting a knowledge gap and a paucity of evidence to guide decision-making. Key issues requiring well-designed up-to-date studies were identified that include optimal approaches to heparin monitoring, assays and reagents to be used, therapeutic range based on indications, the use of weight-adjusted nomograms for initial dosing and titrating of UFH infusion, and indications for antithrombin supplementation. Survey results provide a strong rationale for the development of international guidance addressing these issues.