Abstract: This invention relates to a method for analysis of one or more glycated proteins in a sample, the glycated proteins containing moieties of a natural reducing carbohydrate bound at one or more glycation sites in the proteins, the method comprising: treating the sample with a stable isotopic form of said carbohydrate which is different in mass from the natural carbohydrate, whereby the isotopic form becomes incorporated by glycation in one or more proteins in the sample, and one or more of said proteins are accordingly glycated by the natural reducing carbohydrate and by the isotopic form of the carbohydrate at identical glycation sites; and identifying and/or quantifying the glycated proteins by the difference in mass between the natural carbohydrate and the isotopic form of the carbohydrate at identical glycation sites.