A modified cellulose product comprising cellulose ether, such as carboxymethyl cellulose, hydroxyethyl cellullose, carboxymethyl hydroxyethyl cellulose, methyl cellulose, hydroxyethyl methyl cellulose or ethyl hydroxyethyl cellulose, or xanthan gum product, characterized in that it further comprises salts of aluminium-, ferro-, ferri-, zinc-, nickel-, tin(2)- or tin(4)-cations, and nitrilo-tri-acetic acid, 1,2-cyclo-hexan-di-amin-N,N,N',N'-tetra-acetic acid, di-ethylen-tri-amine-penta-acetic acid, ethylen-di-oxy-bis(ethylen-nitrilo)-tetra-acetic acid, (N-(2-hydroxy-ethyl)-ethylen-diamin-N, N',N',tri-acetic acid, tri-ethylen-tetra-amine-hexa-acetic acid or N-(hydroxyethyl) ethylene-di-amine-tri-acetic acid as a ligand. The product can be used especially as a drilling mud additive.