The article describes a case of spontaneous heparin-induced thrombocytopenia (HIT) after total hip arthroplasty in a patient without previous exposure to heparin[1][4]. HIT is an immune-mediated complication characterized by a decrease in the platelet count by more than 50% compared to the baseline value, typically on days 5-10. day after exposure to heparin[2][4][5]. Despite thrombocytopenia, a high risk of thrombosis, including venous, arterial or microvascular, is present in more than 50% of patients[2][4]. In patients after orthopedic surgery, such as hip arthroplasty, a bimodal decrease in platelets is observed, the first within 5–6 days after the procedure[1]. Pathogenesis involves the formation of antibodies against the PF4/heparin complex, which activates platelets via FcγIIA receptors and increases thrombin generation[1][4]. The risk of HIT is higher after orthopedic procedures, with an incidence of 1–3% in those treated with heparin[4]. Correct diagnosis and immediate discontinuation of heparin are crucial to prevent serious complications such as pulmonary embolism or ischemia[1][5].