Human diabetic patients may have increased lactate levels compared to non-diabetics. Despite the use of lactate levels in critical care assessment, information is lacking for diabetic dogs. Therefore, this prospective cross-sectional clinical study aimed to determine lactate concentrations in 75 diabetic dogs 25 newly diagnosed non-ketotic diabetics, 25 under insulin treatment, and 25 in diabetic ketoacidosis (DKA), compared to 25 non-diabetic dogs. Lactate levels (mmol/L) were not different among groups ( = 0.20); median and 25th to 75th percentile were 2.23 and P = 1.46 to 2.83 for controls, 1.69 and P = 1.09 to 2.40 for newly diagnosed non-ketotic diabetics, 2.27 and P = 1.44 to 2.90 for dogs under insulin treatment for at least 30 days, and 2.40 and P = 1.58 to 3.01 for dogs in DKA. Longitudinal studies assessing both isomers (L- and D-lactate) are needed to better elucidate the role of lactate in the pathophysiology of diabetes acid-base status in dogs.