The focus of this article was to evaluate lipid peroxidation, antioxidant protection, and oxidative stress indicators based on the neutrophil granulocytes functional activity model in children with Type 1 Diabetes Mellitus (T1D). The studies have revealed that, in case of negative effects of reactive oxygen species, children with T1D had intensification in the lipoperoxidation and activation of the antioxidant defense system, including bidirectional changes in non-enzymatic mechanisms. Coordinated generation of reactive oxygen species and oxygen-dependent blood cell metabolism in children with compensated T1D is indicative of the oxidative stress second stage (resistance) development. Reduced production of reactive oxygen species, decrease in the phagocyte oxygen-dependent metabolism activation, incomplete phagocytosis mechanisms correlated with an increase in the pancreas affected area (destruction of insulin-producing β-cells) in children with decompensated T1D, points at the onset of the third stage (depletion) of oxidative stress. Metabolic disorders in children with T1D are determined by the intensity of the “respiratory explosion” of neutrophilic granulocytes in the Lipid peroxidation and antioxidant protection system.