The purpose of this study is to investigate Effect of Melatonin supplement with Non surgical periodontal therapy on periodontal status, some inflammatory markers and serum antioxidant status in type 2 diabetic patients with chronic periodontitis.In this double-blind, single center clinical trial 50 diabetic patients with chronic periodontitis are selected and randomly divided into two intervention (n=25) and control (n=25) groups. Randomization will be done using sealed envelope method. The intervention group will receive two 3 mg Melatonin tablets per day, one hour before bedtime, for 60 days. The control group will receive two 3 mg placebo tablets (containing cellulose, silicon dioxide and starch) one hour before bedtime, for 60 days. Non-surgical periodontal therapy will be performed for all patients during this stud (Below and above the gum scaling). demographic data including age; sex; anthropometric indices such as weight, height, BMI, waist and hip circumference; some serum inflammatory factors (IL-1b, TNF-α),serum antioxidant status includin ((total antioxidant capacity ( TAC), malondialdehyde (MDA), Activity of superoxide dismutase enzyme (SOD), Activity of glutathione peroxidase enzyme (GSHPx), Activity of catalase enzyme )) ; periodontal indices (bleeding index, pocket depth, plaque index and clinical attachment level), physical activity and 3-day 24-hour recall are evaluated pre and post intervention.