Background: In recent years, important advances have been made in the diagnosis of diabetes mellitus, and new strategies have been put forward for its treatment. The purpose of this study was to analyze the cytomorphometric changes and glycogen content in exfoliated cells of oral mucosa as an adjunct in the diagnosis of diabetes mellitus. Method: The smears were taken from buccal mucosa of 30 type 2 diabetes mellitus patients (study group) and 30 healthy individuals (control group). One smear was stained with rapid Papanicolaou stain and the other with periodic acid Schiff stain (PAS). In Papanicolaou stain smears, the nuclear area, cytoplasmic area and cytoplasmic to nuclear ratio were evaluated from 50 cells in each smear using Image analysis software (Q Win Standard, Leica™) and a research microscope (DM 2500, Leica). PAS-stained smears were analyzed for the presence of glycogen in exfoliated cells. Results: The results showed that the mean nuclear area was significantly higher (p < 0.001) in the study group whereas the mean cytoplasmic area did not exhibit a statistically significant difference (p > 0.001). The mean cytoplasmic to nuclear ratio was significantly lower in the study group (p < 0.001). There was a significant increase in the count of PAS-positive exfoliated cells of the study group as compared with the control group (p < 0.001). Conclusion: The results associated with clinical observations suggest that type 2 diabetes mellitus can produce morphologic and functional alterations in oral epithelial cells, detectable by microscopic and cytomorphometric analysis using exfoliative cytology which can be used in the diagnosis of the disease.