A short review provides basic information about the influence of glycation of plasma proteins, as a complication of uncompensated diabetes mellitus, on binding parameters of drugs from various pharmacological groups. There are many facts about the influence of diabetes on binding sites of plasma proteins, but only a relation between the free fraction of sulphonamides and the degree of albumin glycation was described. Observed changes of free fractions of other drugs in diabetic patients are related rather to a competition of these drugs with free fatty acids or other endogenic metabolites for albumin binding sites than to glycation reaction itself. A current clinical status and results of biochemical and pharmacokinetic analyses are necessary for an objective survey of efficiency of pharmacological treatment in diabetic patients.