Lithium is the main mood stabilizer in bipolar disorders and other psychiatric conditions. However, lithium levels in blood must be monitored frequently during therapies because of its narrow therapeutic range. For this reason the patients, whose quality of life is already significantly affected by the disease, must have frequent check-ups in hospitals and undergo painful procedures. In this work an innovative non-invasive method to monitor lithium levels in sweat is proposed. The system is based on a flexible electrochemical sensing platform with platinum nanostructures that enable efficient sensing in perspiration.