A method for diabetes care, the method (which also may be referred to as, involve or incorporate at least one of a tool, device or program) allowing for the characterization of the relevance of errors of parameters affecting glucose concentration on a postprandial glucose concentration outcome for a person with diabetes mellitusm, wherein the method involves at least one of sensing, determining, calculating, predicting, describing and communicating the effects of potential errors of parameters affecting glucose concentration on postprandial glucose concentration values within a clinically relevant glucose range.