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This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. © 2022 The Authors. British Journal of Haematology published by British Society for Haematology and John Wiley & Sons Ltd. Summary Argatroban is a firstline anticoagulant for patients with heparininduced thrombocytopenia (HIT). Published data on practical aspects of its use in HIT are lacking. We aim to establish recommendations based on our experience. This cohort of 32 patients is the largest describing cases of HIT confirmed by a functional assay treated with argatroban. Among patients with normal liver function, median starting argatroban doses (SAD) of 0.54, 0.98, and 1.27 μg/kg/min reached steadystate plasmatic argatroban concentrations (PAC) of 0– 0.39, 0.40– 0.99, and 1.00– 1.5 μg/ml, respectively. Median argatroban dose increases (ADI) induced similar median steadystate PAC increases (Δ μg/kg/min ≈ Δ μg/ml). PAC measurements performed more than 240 min after SAD or ADI were significantly higher compared to earlier controls. Quantitative PAC measurements and thrombin time (TT) appeared adequate for monitoring. Thirtyeight percent of the thrombotic events were preceded by PAC below 0.4 μg/ml. Four hours after argatroban discontinuation, median international normalised ratio (INR) decrease was −1.2. We suggest: (i) monitoring argatroban with PAC or TT at least 240 min after SAD and/or AID; (ii) using SAD of 1.0 μg/kg/ min and ADI of at least 0.2 μg/kg/min when liver function is normal; (iii) targeting therapeutic PAC of 0.5– 1.0 μg/ml; and (iv) targeting INR of 3.5– 4.5 when bridging argatroban with vitamin K antagonists. Division of Hematology and Central Laboratory of Hematology, CHUV, Lausanne University Hospital, Lausanne, Switzerland Faculty of Biology and Medicine, UNIL, University of Lausanne, Lausanne, Switzerland Division of Transfusion Medicine and Immunohematology, CHUV, Lausanne University Hospital, Lausanne, Switzerland Division of Hematology and Laboratory of Hematology, Institut Central des Hôpitaux Valaisans, Sion, Switzerland