BACKGROUND: Diabetic ketoacidosis (DKA) is a life-threatening acute complication of diabetes mellitus, most commonly precipitated by infection. Patients with diabetes are at a significantly elevated risk for severe infections and sepsis. Odontogenic infections represent a prevalent but potentially overlooked source of sepsis in this population, given the established bidirectional relationship between diabetes and periodontitis. CASE PRESENTATION: A 57-year-old female with poorly controlled type 2 diabetes presented with a one-week history of left jaw pain and one day of severe dyspnea and lethargy. Examination revealed left submandibular swelling, Kussmaul respirations, and lethargy. Laboratory findings confirmed severe DKA (pH 7.04, β-hydroxybutyrate 7.19 mmol/L) and sepsis (leukopenia, procalcitonin 2.34 ng/mL). Echocardiography demonstrated severe left ventricular systolic dysfunction (ejection fraction 36%) with normal cardiac biomarkers, consistent with sepsis-induced cardiomyopathy (SICM). Imaging identified a left submandibular abscess. Management involved prompt sepsis bundle implementation, including early empiric antibiotics (amoxicillin-clavulanate and tinidazole), aggressive fluid resuscitation, and concurrent intravenous insulin infusion for DKA, alongside proactive electrolyte repletion. Multidisciplinary source control was achieved. Outcomes: The patient showed rapid clinical improvement. Metabolic acidosis and ketosis resolved. Infection markers normalized. Remarkably, follow-up echocardiography on day 14 demonstrated complete recovery of cardiac function (ejection fraction 72%). She was discharged after 15 days and remained well at one-month follow-up. CONCLUSIONS: This case underscores that odontogenic infection can be a potent trigger for life-threatening DKA and septic shock with multi-organ dysfunction in diabetic patients. It highlights the critical importance of thorough physical examination, including oral cavity inspection, in the evaluation of sepsis or DKA. The presentation and complete reversibility of SICM reinforce that treatment must focus on correcting the underlying septic and metabolic insults. Early multidisciplinary management is essential for optimal outcomes.