Objective: This study was designed to evaluate the effect of using L.Reuteri containing tablets, on the gingiva of uncontrolled diabetic rats both histologically and ultrastructurally. Material and Methods: Thirty adult male albino rats were equally divided into three groups, Group I served as control, Group II: rats were subjected to induction of diabetes mellitus using streptozocin, Group III: rats treated as group II animals and on the next day they were fed daily a probiotic tablet Prodentis containing L. reuteri for 14 days. At the end of the experiment, histological and ultrastructural examination was performed on the gingiva. Results: Rats of group II revealed inflammatory gingiva with loss of normal structure, while that of group III revealed a somewhat normal gingiva in comparison to group II. Conclusion: L.reuteri containg tablets can inhibit gingival inflammation associated with diabetics through its antibacterial and autoinflammatory properties.