Latent Autoimmune Diabetes in Adults (LADA) is an autoimmune endocrine disorder in which despite the presence of antipancreatic islets antibodies in the moment of diagnostics, the progression to beta-cell secretory insufficiency is slow. It is often confused with others types of diabetes and therefore the management is frequently inadequate. We report a clinical case of a 23-year-old man with diagnosis of type 2 diabetes since 6 months ago, poorly controlled with a sulfonylurea, who initially presented 2 months ago from polyuria, polydipsia, and asthenia and 6 kg weight loss. History of past illness was negative, however, his mother relates exclusive breastfeeding during the first 15 days of life and later (until the 6 months) he was fed with infant formula (S-26). Family history revealed a first-degree relative (father) with diabetes mellitus secondary to steroid administration due to diagnosis of bone marrow hypoplasia. Also presents second-degree family history (uncle and grandfather) of type 2 diabetes mellitus. There were no pathologic findings at the physical examination. Anthropometry and laboratory tests were as follows: body mass index (BMI) = 19.66 kg/m, basal and postprandial glycemia = 108, and 276 mg/dL respectively, glycated haemoglobin = 8.9%, basal and postprandial C-peptide (2 hours) = 1.9, and 3.2 ng/mL, homeostasis model assessment of beta cell function: 87.5%, homeostasis model assessment of insulin resistance: 1.6. LADA presumptive diagnosis was confirmed with presence of autoantibodies anti-tyrosin-phosphatase and GAD65. At the time of diagnosis, individuals with LADA present an onset age <50, BMI <25 kg/m2, low magnitude postprandial and basal hyperglycemia, normal or close to normal C-peptide values, and thus not occur with acute hyperglycemic crises. Insulin therapy preserves pancreatic b-cell function, at the point that eventually prescribed insulin doses need to be reduced.