Abstract Background Fluctuations in blood glucose level cause endothelial dysfunction and play a critical role in onset and/or progression of atherosclerosis. We hypothesized that fluctuation in blood glucose levels correlate with vascular endothelial dysfunction and that this relationship can be assessed using common bedside medical devices. Methods Fluctuations in blood glucose levels were measured over 24 hours by continuous glucose monitoring (CGM) on admission day 2 in 57 patients with type 2 diabetes mellitus. The reactive hyperemia index (RHI), an index of vascular endothelial function, was measured using peripheral arterial tonometry (EndoPAT) on admission day 3. Results The natural logarithmic-scaled RHI (L_RHI) correlated with SD (r=−0.504; P &lt;0.001), the mean amplitude of glycemic excursions (MAGE) (r=−0.571; P &lt;0.001), mean postprandial glucose excursion (MPPGE) (r=−0.411; P =0.001) and percentage of time ≥200 mg/dl (r=−0.292; P =0.028). In 12 patients with hypoglycemia, L_RHI also correlated with the percentage of time at hypoglycemia (r=−0.589; P= 0.044). L_RHI did not correlate with HbA1c or fasting plasma glucose levels. Furthermore, L_RHI did not correlate with LDL cholesterol, HDL cholesterol, and triglyceride levels or with systolic and diastolic blood pressures. Finally, multivariate analysis identified MAGE as the only significant determinant of L_RHI. Conclusions Fluctuations in blood glucose levels play a significant role in vascular endothelial dysfunction in type 2 diabetes. Trial registration UMIN000007581

Relationship between fluctuations in glucose levels measured by continuous glucose monitoring and vascular endothelial dysfunction in type 2 diabetes mellitus