Background __ampersandsignamp; Aims: Low serum concentrations of the osteocalcin (OC), haemoglobin and osteoporosis is associated polyarthritic and systemic subtypes of the juvenile idiopathic arthritis (PJIA, SJIA) with the combination of type 1 diabetes mellitus (T1DM). We investigated the association of serum OC levels with JIA and the influence of T1DM on this association in participants. Our goal is to study, analyze, and update and introduce new therapeutic techniques into the underlying disease characteristics of chronic rheumatic diseases that are most commonly observed in childhood. Methods: This study compares concentrations of osteocalcin (OC) between participants with PJIA, SJIA and type 1 diabetes (T1DM) (n=20) and age-, gender- and body mass index (BMI)-matched participants without T1DM (n=40) among patients with OJIA (oligoarthritic the juvenile idiopathic arthritis), and it explores relationships between OC concentrations JIA and T1DM. Quantitative evaluation of OC was measured in heparin-treated blood plasma by IMMULITE 2000 analyzers. This in vitro study used to monitor mineral metabolism and diagnose osteoporosis. The IMMULITE OC test allows determining only an unfragmented OC molecule, not fragmented ones. Results: Concentrations of OC were very low in participants with PJIA, SJIA with the combination of T1DM. In OJIA patients without T1DM, concentrations of OC were roughly at normal average. Conclusions: In patients with PJIA and SJIA, lower OC concentrations were related to T1DM.OC was sufficient to predict and prevent osteoporosis in JIA patients with a combination of T1DM. Serum level of OC administered in patients with OJIA without T1DM was in the region of the normal range. No relationship was detected between serum OC levels and OJIA in participants.