Abstract: Disclosed is the use of a DKK1 gene or the coded protein inhibitor thereof for the preparation of a composition or formulation used to prevent and/or treat tumor cachexia and diseases associated with diabetes. By inhibiting the expression or activity of the DKK1 gene or the protein encoded thereby in tumor cells, which can effectively prevent and/or treat tumor cachexia and diseases associated with diabetes, also provided is a method for detecting the protein expression level of DKK1 in blood, which level is taken as an indicator for precise treatment and judging prognosis.