PIK3CA and diabetes mellitus: This case describes the unique presentation of a patient with no prior history of diabetes who presented with DKA after starting alpelisib, and returned to euglycemia off of insulin just three days after stopping the drug suggesting that alpelisib can cause DKA in patients who did not previously have diabetes, and that the hyperglycemia is completely reversible upon discontinuation of the PIK3CA inhibitor and consequent restoration of the PI3K/AKT pathway.