Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction with significant thromboembolic risk. Though there are models for use of non-heparin anticoagulants, heparin remains the preferred anticoagulant in many operative settings, especially cardiovascular surgery and percutaneous cardiac intervention. The natural history of HIT can be stereotyped into phases using HIT laboratory testing to guide clinical management and determine whether heparin re-exposure can be considered. In acute HIT and subacute HIT A (immunoassay positive, functional assay positive) when thromboembolic risk is high, non-urgent procedures should be delayed, if feasible. If procedures cannot be delayed, approaches include intraoperative bivalirudin or intraoperative heparin with pre- or intra-operative plasma exchange or a potent antiplatelet agent, sometimes in combination with intravenous immunoglobulin. In subacute HIT B (immunoassay positive, functional assay negative) and remote HIT (immunoassay negative, functional assay negative), brief exposure to heparin in the intraoperative setting with close monitoring post-operatively is suggested due to the low risk of recurrent HIT.