Heparin Induced Thrombocytopenia (HIT) is not a rare condition. Large numbers of acutely ill patients now receive heparin, and unfractionated heparin (UFH) results in HIT 3% of the time. It is a pro-thrombotic disorder, therefore it is often interpreted as failure of anticoagulation to prevent DVT rather than the cause of DVT. Further treatment with standard anticoagulation therefore results in further misadventure. Platelet counts should always be followed in patients on UFH.