The invention concerns a method for stabilizing the content of glycated protein in a sample on a matrix material, which is characterized in that the matrix material is impregnated with boric acid buffer with a pH which is larger or equal to 10.5 or a transition metal salt as well as an appropriate matrix material, an element for collecting, transporting and storing sample material to be analysed with such a matrix material and a system containing such an element and a sealable covering.