BackgroundBlood glucose is tightly regulated in horses; however, since hypoglycaemia and hyperglycaemia are associated with poor prognosis, close monitoring is warranted. This study aimed at evaluating a continuous indwelling glucometer (CIG) by comparing performance with a point-of-care glucometer (POC).MethodsTen horses were equipped with CIG and an intravenous catheter. Interstitial glucose concentrations were determined by CIG every 5 min at rest, during insulin-induced hypoglycaemia and dextrose-induced hyperglycaemia, and compared with blood glucose determined by POC. Glucose concentrations were compared by two-way repeated measures analysis of variance and weighted kappa with Bland-Altman plots to determine agreement between assays.ResultsHorses tolerated CIG well; however, five devices had to be replaced. There were no statistically significant differences between assays at rest or during hyperglycaemia; however, during hypoglycaemia, glucose concentrations determined by CIG were significantly higher (P=0.01). The mean bias (95% limits of agreement) between assays ranged from −0.03 (−2.46 to 2.52) mmol/l (hyperglycaemia) to 0.97 (−1.23 to 3.16) mmol/l (hypoglycaemia). Assay agreement was ‘good’ with observed agreements of 87.04% (κ=0.67).Conclusions of the studyCIG has acceptable accuracy in horses as compared with POC but overestimates glucose concentrations during hypoglycaemia and requires frequent replacement, limiting its clinical application.