Type 1 diabetes mellitus is a major endocrine disorder, affecting approximately 5% of the world's population. It not only leads to hyperglycaemia but also causes many complications, and numerous studies have demonstrated that oxidative stress contributes to these complications. As a new strategy to improve the oxidative damage in diabetes, interest has grown in the usage of natural antioxidants, even more in the long term. Among them, Rosmarinus officinalis (rosemary) has been widely accepted as one of the species with the highest antioxidant activity. In addition, omega-3 polyunsaturated fatty acids were efficient in delaying and decreasing cardiovascular risk factors associated with diabetes. Type 1 diabetic children and the corresponding controls were enrolled in the assay. The aim was evaluating the effect of a special additive containing rosemary extract, vitamin E and PUFAs added to their standard diet through the meat. In the analytical point of view, a metabolomic approach with CE-UV was used to detect possible differences in urine of diabetic children as compared to controls. After the application of the appropriate multivariate statistical tools, clear differences could be observed between treated and non-treated diabetic children and some of the metabolites associated could be identified. This was specially challenging as most of the clinical biochemical parameters measured by target analysis showed no differences between the groups.