This disclosure features microspheres and a method of making them. The microspheres are for sustained release of an octreotide compound with a low initial burst, comprising a poly(D,L-lactide-co-glycolide) polymer matrix and an octreotide compound dispersed in the polymer matrix. The microspheres release less than 1% of a total amount of the octreotide compound within 1 hour at 37° C. and pH 7.4.