Introduction and aim: Alpelisib is approved for metastatic breast cancer with phosphatidylinositol-3 kinase subunit alpha mutation. While hyperglycaemia is a common complication of Alpelisibuse , Diabetic ketoacidosis is rare . With increasing number of patient being provided the benefit of this drug , the number of cases being reported with DKA are also increasing in number . With this study we aimed to identify and expand the spectrum of clinical picture for this condition Methods: Data from consecutive emergency admission with a diagnosis of Diabetic ketoacidosis was analysed for patients with breast cancer and on Alpelisib . Those with associated secondary factors for Diabetic ketoacidosis were excluded . A total of 5 cases were considered forfinal analysis. Results : We observed diabetic ketoacidosis in one non diabetic and four well controlled type 2 diabetic patients.Most patient developed diabetic ketoacidosis within 30 days of Alpelisibinitiation . Nausea and vomiting were the most common presentation. On discontinuation of the drug , hyperglycaemia resolved within 3 days . Ondrug rechallenge at a lower dose of 250 mg , all patient developed hyperglycaemia but only one patient redeveloped diabetic ketoacidosis , Rest of patient were well controlled on a combination of oral antidiabeitic drugs with only one patient requiring insulin Conclusion: Alpelisib is a promising drug for eligible patients of metastatic breast cancer ,however these patients should be closely monitored for hyperglycaemia . Diabetic ketoacidosis is a rare complication and require multidisciplinary approach to manage . Most patients can be managed well with oral antidiabetic agents once diabetic ketoacidosis resolves.