Disclosed herein are diketopiperazine microparticles having a specific surface area of less than about 67 m2/g. The diketopiperazine microparticle can be fumaryl diketopiperazine and can comprise a drug such as insulin.本文揭示比表面小於約67平方公尺/公克之二酮基哌微粒子。二酮基哌微粒子可為反丁烯二醯基二酮基哌且可包含諸如胰島素之藥物。