Curcumin may be an anticoagulant, which could make the effects of some blood thinner medications (e.g., warfarin) more potent. It may also have antiplatelet activity and increase the effects of medications that prevent platelet aggregation (e.g., acetylsalicylic acid/aspirin). Both of these interactions could lead to an increased bleeding risk and other adverse events. However, there aren’t many clinical (human) trials that have confirmed these interactions, and the few available studies are of poor quality or are funded by the company which manufactures the curcumin supplement; therefore, caution is warranted until more research is performed on these interactions.[1][2]
In vitro and animal studies have also noted that curcumin may reduce the activity of certain chemotherapy agents. The mechanism of action is still unclear, but it might be related to the dose of curcumin given.[2]