If you are currently being treated with any of the following medications, you should not use quercetin supplements without first talking to your healthcare provider.

Chemotherapy
Test tube and animal studies suggest that quercetin may enhance the effects of doxorubicin and cisplatin, two chemotherapy medications used to treat cancer. More research is needed to determine if quercetin has any application to people being treated with either of these agents. In addition, use of antioxidants at the same time as chemotherapy is somewhat controversial. Therefore, more research is needed before conclusions about safety and effectiveness can be drawn.