Non-surgical Periodontal Therapy in Diabetes Patients with Chronic Periodontitis Aim: Diabetes mellitus is a metabolic disorder which increases the risk for developing infections such as periodontitis. There is two-way relationship between diabetes and periodontitis. It is expected that periodontal treatment improves metabolic control of diabetes. The aim of this study was to evaluate the effect of the periodontal treatment on the metabolic control of diabetes type II and the clinical periodontal parameters. Methods: Non-surgical periodontal therapy including oral hygiene motivation, scaling and root planing are applied to total of 31 volunteer patients who suffer from periodontitis and type II diabetes mellitus. These patients were divided into two groups. The patients in experimental group were prescribed 100 mg doxycycline once a day and chlorhexidine mouth-rinse twice a day for fourteen days starting on the day of the first session of the treatment. Assessments were performed prior to and following the 3rd month of the treatment. Results: There is no statistically significant decrease was observed in the clinical periodontal parameters (P>0.05), except GI (P<0.05) during the treatment. When the changes of parameters due to the treatment were evaluated, FBG was significantly found to be lower in experimental group compared to the control group (P<0.05). Statistically significant decrease was observed in the clinical periodontal parameters of both groups and in the levels of HbA1c of experimental group (P<0.05). Conclusion: The results of our study revealed that, doxycycline and chlorhexidine usage as an adjunct to non-surgical periodontal therapy in diabetic patients were found to be ineffective when clinical periodontal parameters and metabolic control parameters were evaluated. Further longitudinal studies and largest populations will help to elucidate this subject.