Abstract: The present disclosure reveals the diagnostic method for the determination of multiday average molar concentration of estradiol (E2) and from this parameter, the assessment of perimenopause and menopause status in examined female subjects, based on quantitative analysis of N-glycans bound on immunoglobulin G (IgG). The diagnostic process is applicable to the female subjects of 40-55 years of age. The revealed method enables the determination of the multiday average molar concentration of estradiol (E2), which is an important diagnostic parameter hardly accessible by any known single diagnostic method applied on only one or more blood analyses.