We describe a 37 year-old woman case of latent autoimmune diabetes in adults (LADA). She was presented with unfounded weight loss. The diagnosis of diabetes mellitus was established on twice plasma glucose measurements above 200 mg/dl. In other routine biochemical examinations we did not observe dehydratation, electrolyte depletion, acidosis. However plasma level of C peptide basal and after stimulation with glucagon was reduced. Initially, the patient responded well to sulphonylurea treatment. To test immunological pathogenesis we examine autoimmune markers of diabetes type 1. Autoimmune antibodies (GAD, IAA) were found in patients and her parents, which were until now diabetic type 2. We report this case because incidence of latent autoimmune diabetes in adults is underestimate and rarely diagnosed in clinical practice.