Low Blood Oxygen Saturation (BOS) is associated with increased overall morbidity / mortality and prevalence of diabetes is known to increase with altitude (lower 02 partial pressure). Individuals with complicated diabetes commonly have low blood oxygen saturation compared with nondiabetic patients. To unravel the link between low BOS and glucose metabolism, we investigated the correlation between BOS and glucose, BOS and HbA1c levels, BOS and VO2 consumption (Resting Energy Expenditure) in a cohort of adults with diabetes mellitus. The study included 1362 adults with diabetes (616 F, 746 M; 66.4 ± 14.2 years, range 18-85 years; BMI 27.6 ± 5.0 kg/m2, range 18-49.6 kg/m2; SpO2 97.2 ± 1.4%, range 88-100%; glucose 137.7 ± 45.0 mg/dl, range 50.0-323.0 mg/dl). A significant inverse correlation (Pearson) between the glucose (glucometer) and the BOS (pulsoximeter) (p<0.0001*; r = -0.1530). An inverse correlation (Pearson correlation) between the HbA1c levels and the BOS (n=1295; 568 F, 727 M; 67.5 ± 13.1 years, range 18-85 years; BMI 27.8 ± 5.2 kg/m2, range 18-49.8 kg/m2; HbA1c 52.9 ± 13.0, range 25-152 mmol/mol; p<0.0001*; r = -0.1351). In summary, we showed an inverse relationship between oxygen saturation and both glucose and glycosylated hemoglobin levels. Although the exact mechanisms behind lower blood oxygen saturation in diabetes are unknown, we speculate that a reduced pulmonary diffusion capacity as a consequence of pulmonary microvascular damage could play an important role. In conclusion, present preliminary data indicate the routine measurement of BOS along with glucose and glycosylated hemoglobin in the outpatient visit setting of diabetic patients as a biomarker of seriousness of disease. Disclosure L. Luzi: Speaker's Bureau; A. Menarini Diagnostics, Amgen Inc., Boehringer Ingelheim and Eli Lilly Alliance. Advisory Panel; Eli Lilly and Company. Speaker's Bureau; Eli Lilly and Company. Research Support; Gelesis. Advisory Panel; Medtronic. Speaker's Bureau; Novo Nordisk, Novartis. C. Macrì: None. A. Ferrulli: None. C.C. Berra: None. C. Romano: None. S. Massarini: None. Funding IRCCS MultiMedica (Ricerca Corrente)