Abstract
The paper demonstrates how the wrong classification of diabetes mellitus leading to long term incorrect treatment and fixation on wrong lifestyle habits. The disease of a 15 years old boy was incorrectly diagnosed as a type 1 diabetes mellitus and treated with insulin from the beginning.
More than 20 years later, based on examinations of C-peptide, autoantibodies and other markers, the disease was reclassified to diabetes mellitus type 2 with dominating insulin resistance and the treatment was adequately changed.