Abstract: This invention relates to potentiating insulin activity in a patient in need thereof. This invention provides a composition comprising an insulin potentiating agent; such composition comprises one or more substance derived from a water extract of Polygonum multiflorum, Agaricaceae, or Cinnamomum mairei. This invention also provides a method for treating hyperglycemia in a patient by administering to the patient an insulin potentiating agent. The method can be used to decrease blood glucose and/or glycosylated hemoglobin and/or glucose level.