Diabetes mellitus (DM) affects 2-37% of patients with chronic obstructive pulmonary disease (COPD), with results being highly variable between studies. DM may also correlate with disease characteristics.The aim of this study was to examine the prevalence of DM and its correlation with comorbidities and COPD characteristics in patients with COPD admitted for exacerbation. 152 patients were studied for presence of DM. All of them were (13/44) of females (p=0.379). The prevalence of DM in this study is significantly higher when compared to an unselected Bulgarian population (12,8% in subjects over 45 years).91% of patients with newly discovered diabetes had glycated hemoglobin (HbA1c)≥6,5% suggesting prolonged hyperglycemia. There is a correlation between the presence of DM and MS (p=0.008). The presence of DM is associated with more severe exacerbations (hospitalizations) during the previous year (p=0.003) and a longer hospital stay (p=0.006).DM is not associated with reduced quality of life and worse pulmonary function. The patients with COPD admitted for exacerbation are at great risk for impaired glucose metabolism which is associated with worse COPD characteristics. The majority of the patients in this study are unaware of having DM.PeerJ PrePrints | https://dx.doi.org/10.7287/peerj.preprints.939v1 | CC-BY 4.0 Open Access |