A kind of health supplement for lowering plasma glucose and plasma triglyceride is prepared from a mixture of dried grape skins with the flesh removed, dried grape seeds and dried grape stems, and the mixture is ground into fine powder (termed 3SG powder) according to a ratio of volume between the grape skins, the grape seeds and the grape stems found in naturally available grapes; upon treatment of the 3SG powder with ethanol, the intracellular lipid-soluble flavonoids of the 3SG powder are released to give rise to the health supplement which functions include to lower plasma glucose and plasma triglyceride, as well as to attenuate anomalous energy metabolism in diabetic, hyperglycemic, and hyperlipidemic people.