A method for treating Parkinson's disease where insulin and GSH may be administered intranasally. The GSH and insulin that is administered may be in varying doses at least once daily. The GSH and insulin may be administered sequentially and/or simultaneously and the medications may be administered for differing periods of time depending upon a patient's tolerance and response to the GSH and insulin. The GSH and the insulin may be administered for a certain period of time and/or indefinitely.