Venous thromboembolism prophylaxis with subcutaneous unfractionated heparin or low molecular weight heparin is a common practice in hospitalized patients. Typically, prophylactic doses of these medications have poor bioavailability and thus do not reach therapeutic serum concentrations. However, in certain circumstances, heparin binding proteins may become saturated. Here we report a case series of 5 patients who had elevated anti-Xa levels while receiving prophylactic dosing of subcutaneous unfractionated heparin.
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