Little information is available comparing the i-STAT and the YSI 2300 Stat Plus devices to determine the lactate concentration [Lac] in dogs undergoing intense exercise. The reproducibility of the YSI 2300 for quantifying the [Lac] in canine blood [Lac]_b and plasma [Lac]_p samples has been observed. In addition, the i-STAT handheld device was used to quantify [Lac] in dogs subjected to exercise, and the results were compared with that of YSI 2300. Venous blood samples of Beagle and American Pit Bull Terrier dogs were obtained during an intense exercise training on a treadmill. [Lac]_p and [Lac]_b were quantified using the YSI 2300 instrument to determine the reproducibility of the results. A total of 52 specimens were compared for both plasma and whole blood. For comparing the devices (YSI 2300 vs i-STAT), 96 samples were used. Ordinary least products regression, the correlation coefficient, and Bland-Altman plots were used to assess the agreement of using the i-STAT device. The relationship between duplicate measurements of both [Lac]_b and [Lac]_p by YSI 2300 was strong (r=0.99). A correlation between the data obtained using the i-STAT and YSI 2300 instruments was observed for both the [Lac]_p (r=0.97) and [Lac]_b (r=0.88). The i-STAT exhibited a small constant bias (-0.25 mmol/l) compared to YSI 2300 ([Lac]_b). There were proportional biases of 0.89 mmol/l for [Lac]_p and 1.22 mmol/l for [Lac]_b when using YSI 2300 vs i-STAT. We confirmed the reproducibility of the YSI 2300 for canine lactate blood/plasma samples. The results obtained by the i-STAT and YSI 2300 analyser were highly correlated, but a small constant bias was observed between them. The i-STAT device can be used in clinical evaluations, and it is also adequate for designing and monitoring fitness programmes.