The potential of antioxidants as tools for lowering the incidence of diseases, including cardiovascular events, is of growing interest. Some antioxidants (e.g. vitamin E and acetyl-salicylic acid) have been described as effective on cardiovascular diseases with mechanisms that differ from other scavenging agents. Currently, vitamin C is used to open occluded long-term central venous catheters, which avoids the process of reinserting a new one and injuring the patient. In this work, we investigated the vitamin C antihemostatic profile by evaluating its effects on the coagulation process. We used different assays, including prothrombin time (PT), activated partial thromboplastin time (aPTT), thrombin time (TT) and ancrod time tests. We also examined the overall pH disturbance caused by vitamin C at different concentrations and its effect on the thrombin-initiated fibrin polymerization assay. Our results revealed a significant anticoagulant activity of vitamin C at high plasma concentrations (surpassing the normal 100 ?mol/L ratio) in a cell-independent mechanism. Our results suggest that vitamin C may affect blood coagulation by a direct impairment of fibrin assembly and further formation of a cohesive clot microstructure. This study supports the literature that points to the antihemostatic ability of antioxidant agents, and clarifies the mechanism of vitamin C in opening occluded long-term central venous catheters.