Chemosensory dysfunction has been reported in patients with diabetes mellitus (DM). However, the clinical significance in relation to the disease stage remains unclear. The aim of this investigation was to assess olfactory and gustatory function with valid clinical tests in patients with DM types 1 and 2 with and without accompanying diseases. Seventy-six patients with DM were divided into three groups according to disease stage. Taste function was tested by means of impregnated paper strips and smell function was screened using a five-item smell identification test. The results of the patients with uncomplicated DM were compared with the results from 29 healthy subjects. The results showed no significant differences in smell and taste function between patients with uncomplicated DM and healthy subjects. However, patients with additional diseases exhibited decreased smell acuity. Moreover, patients with DM type 2 showed impaired smell function compared with patients with DM type 1.