The invention relates to an oligosaccharide having a weight average molecular weight (Mw) of less than 3,000 Daltons, wherein said oligosaccharide comprises functional aldehyde groups and has a dimer saccharide content of 2.9 % by weight or less, based on the total weight of the hydrogenated oligosaccharide. The invention also relates to a process for preparing the oligosaccharide, which process comprises the steps of: hydrolysing a polysaccharide so as to reduce its molecular weight, wherein the resulting oligosaccharide comprises functional aldehyde groups, and fractioning the oligosaccharide according to molecular weight, so that the purified fraction has a weight average molecular weight equal to or less than 3,000 Daltons. The procedure of purification is performed by one or more membrane processes, having a cut-off value between 340 and 800 Daltons, which procedure is continued until the content of dimer saccharide in the purified fraction of oligosaccharide has been reduced to 2.9 % by weight or less, based on the total weight of the hydrogenated oligosaccharide.La présente invention concerne un composé oligosaccharide associé au fer ayant une stabilité améliorée comprenant un oligosaccharide hydrogéné en association stable avec de l'oxyhydroxyde ferrique, la teneur en disaccharide dans ledit oligosaccharide hydrogéné étant inférieure ou égale à 2,9 % en poids, en se basant sur le poids total de l'oligosaccharide hydrogéné. Dans d'autres aspects, la présente invention concerne un procédé de préparation dudit composé ainsi que l'utilisation dudit composé dans la préparation d'une composition destinée au traitement de l'anémie ferriprive.
