Objectives The main aim of this study was to compare two days of continuous monitored capillary blood glucose (CGM) responses to sitting and standing in normally desk-based workers. Design, setting and participants This open repeated-measures study took place in a real office environment, during normal working hours and subsequent CGM overnight measures in 10 participants aged 21-61 years (8 female). Main outcomes Postprandial (lunch) measures of: CGM, accelerometer movement counts (MC) heart rate, energy expenditure (EE) and overnight CGM following one afternoon of normal sitting work compared with one afternoon of the same work performed at a standing desk. Results Area-under-the-curve analysis revealed an attenuated blood glucose excursion by 43% (p=0.022) following 185 min of standing (143, 95% CI 5.09 to 281.46 mmol/L min) compared to sitting work (326; 95% CI 228 to 425 mmol/L min). Compared to sitting, EE during an afternoon of standing work was 174 kcals greater (0.83 kcals/min; p=0.028). The accelerometer MC showed no differences between the afternoons of seated versus standing work; reported differences were thus a function of the standing work and not from additional physical movements around the office. Conclusions This is the first known 'office-based' study to provide CGM measures that add some of the needed mechanistic information to the existing evidencebase on why avoiding sedentary behaviour at work could lead to a reduced risk of cardiometabolic diseases.