A method for manufacturing a modified hydroxyethyl starch carrying a heptonic acid residue on at least one of its termini is disclosed. Within this method, the following steps are carried out: a) dissolving hydroxyethyl starch in water, b) adjusting the pH value to a value of 8.0 to 10.0, c) adding a cyanide compound to the hydroxyethyl starch solution, heating the solution to a temperature of 80 to 99° C. and keeping it at this temperature for a first time period, and d) adjusting the pH value to a value of 2.0 to 4.0, bringing the solution to a temperature of 50 to 90° C. and keeping it at this temperature for a second time period.
