Introduction: Local anaesthesia (LA) is the usual drug used in dentistry to reduce intraoperative pain. The efficacy of lignocaine is improved by adding adrenaline as a vasoconstrictor. Adrenaline decreases the systemic absorption of LA and reduces blood loss during the surgical procedure. The study was conducted to observe the effect of adrenaline on blood glucose concentration in patients undergoing tooth extraction. Materials and Methods: The study was conducted on 100 patients needing multiple teeth extraction. On the first appointment, extraction was done using lignocaine without adrenaline (plain), and for the second appointment, extraction was done using lignocaine with adrenaline (1:200,000). Serial blood glucose estimations were carried out at identical intervals on both occasions. Results: Significant difference in blood glucose level was noted when the patients received lignocaine with adrenaline before administration and after 10 min/20 min intervals ( P < 0.05). Discussion: Constant vigilance and prudence are recommended while using lignocaine with adrenaline in patients suffering from diabetes mellitus.