Glycosylation is a co- and post-translational modification that affects the folding, solubility, structure, and function of proteins. N-glycosylation produces complex and hybrid subtypes of N- glycans that are present on most glycoproteins, while the high-mannose subtype is less common. Research has shown that changes in protein glycosylation accompany pathological conditions such as cancer, diabetes, aging, and others, giving them potential as diagnostic markers. The C3 component of complement is a glycoprotein that contains two glycosylation sites with high- mannose glycans. The role of this protein in immune processes, which underlie the development of many diseases, is indisputable. Previous studies have identified differences in the prevalence of certain high-mannose glycoforms in diseased subjects. In this study, for the first time, interindividual differences in the glycosylation of the C3 protein in healthy subjects were analyzed to establish a basis for further research into its diagnostic potential. The hypothesis of the study is that the glycosylation of the C3 glycoprotein depends on the age and sex of the subjects, as has been shown for some other proteins studied. An LC-ESI-MS analysis of enriched glycopeptides was conducted to determine the prevalence of 9 high-mannose glycoforms in 162 subjects of both sexes, ranging in age from 20 to 85. The results of the analysis showed statistically significant, though not pronounced, interindividual differences in 5 glycoforms with respect to the sex of the subjects. Age had almost no influence on the glycosylation of the C3 glycoprotein in the studied population, although this influence slightly increased when the subjects were divided by sex. Although it should not be overlooked in the evaluation of diagnostic potential, the relatively low influence of age and sex on the glycosylation of the C3 glycoprotein makes it a more robust potential diagnostic marker compared to other glycoproteins studied so far.