BACKGROUND: Diabetic ketoacidosis (DKA), an acute and potentially life-threatening complication of diabetes mellitus, is frequently the result of a precipitating illness or nonadherence to treatment; however, despite a thorough history, physical, radiologic, and laboratory examination, a specific cause or precipitating event cannot be identified in a significant number of cases. AIMS: To report 2 cases of recurrent DKA, and hyperglycemic crisis, associated to the menstrual cycle, and provide a review of the medical literature. METHODS: The clinic and hospital medical records of 2 subjects with type 1 diabetes mellitus (T1DM) and unexplained DKA are reviewed. An electronic MEDLINE search of relevant medical literature published from 1965 to 2007 was performed; additionally, the reference lists of the identified articles and other sources, such as textbook chapters and meeting abstracts, were reviewed for related publications. RESULTS: To date there have been 7 reported cases in the literature demonstrating an association between menstruation and DKA. The 2 new cases presented here highlight the potentially significant changes in glucose metabolism that may occasionally be observed during the late luteal and decidual phases of the menstrual cycle; moreover, these cases underscore the importance of a thorough medical and gynecologic history when evaluating a patient with DKA. CONCLUSION: Through unclear mechanisms, some women with diabetes mellitus demonstrate significant changes in glucose control around the time of their menses, including DKA. Accordingly, we propose that the terms catamenial DKA and catamenial hyperglycemia be used to refer to these disorders and that catamenial DKA be included in the differential diagnosis list of causes or precipitating events that can lead to DKA. © Copyright 2008 Southern Society for Clinical Investigation.