Introduction: Flare-ups is the phenomenon which may develope during Endodontic Procedures. It commenses within few hours or days during root canal treatment, characterised by pain and swelling, requiring unscheduled emergency visit. Non Insulin dependent Diabetes mellitus predisposes to chronic inflammation due to alteration in immune function. Diabetic patients have higher propensity for severe Endodontic infection and increased incidence of flare-ups. Aim: To compare the incidence of interappointment flare-ups during Endodontic treatment in Diabetic and in Non Diabetic patients. Methodology: The medical history and Endodontic treatment data for non surgical Endodontic patients treated in ADC R&R from June 01 2017 to Dec 31 2017 were recorded. A total of 2164 cases (including 151 Diabetic patients and 650 patients with Hypertension) were treated. After initiation of treatment, cleaning and shaping were completed and intracanal calcium hydroxide dressing was placed. Next sitting was scheduled after 3 days. Results: Patients with Diabetes have higher incidence of flare-ups than with patients without any metabolic disorder. Conclusion: The study revealed that Interappointment Flare-ups in patients with Diabetes is higher than in patients without Diabetes.