Ludwig?s angina is a serious and rapidly progressive infectious process that spreads through the floor of the mouth and neck. In this paper we present an infrequent case of a patient who suffered an odontogenic infection with poor response to the previous treatment, which evolved towards a Ludwig?s angina combined with ketoacidosis in the context of a diabetes mellitus not known before. According to the literature reviewed, this case report represents the first contribution of a Ludwig?s angina and ketoacidosis as an initial manifestation of a diabetes mellitus. The airway management, the antibiotic prescription and the surgical drainage allowed the healing of the patient without medical complications. Factors of co-morbidity like the diabetes mellitus together with focus tooth of infection may eventually turn into serious medical complications as the diabetic ketoacidosis and develop potentially lethal cervical infections.