Although precise and accurate laboratory methods are available for quantifying circulating β-hydroxybutyric acid (BHB), dairy producers would benefit from having an accurate cow-side tool to quickly diagnose ketosis. Therefore, the objective of this study was to validate a handheld electronic BHB meter (BHBCheck; PortaCheck, Moorestown, NJ) in the diagnosis of hyperketonemia using a colorimetric laboratory assay as reference (LiquiColor Assay; EKF Diagnostics-Stanbio, Boerne, TX). Blood samples were collected from multiparous Holstein cows (n = 112) in the peripartum period at −7, 7 and 14 d relative to calving date in a commercial herd in Northern Mexico. Whole blood was obtained by venipuncture from the coccygeal vein/artery and BHB concentration was directly measured with the BHBCheck meter; blood samples were collected at the same time in sterile evacuated tubes with no coagulating agent, centrifuged to obtain serum, and frozen −20°C until further laboratory analysis. Data were analyzed using the UNIVARIATE, FREQ, and REG procedures of SAS for descriptive statistics, sensitivity and specificity, and regression analysis, respectively. Concentration of BHB ranged from 0.30 to 5.20 mmol/L and averaged 0.87 ± 0.47 mmol/L (±SD) for the BHBCheck whereas the laboratory assay ranged from 0.21 to 5.24 mmol/L with a mean of 0.79 ± 0.49 mmol/L. The overall correlation coefficient (r) for the concentrations obtained with the BHBCheck and the laboratory assay was 0.86; when correlation was tested by day of sampling, the coefficients were 0.47, 0.80, and 0.92 for d −7 (n = 112), 7 (n = 107), and 14 (n = 106) respectively. The proportion of samples with BHB ≥1.2 mmol/L was 12.0% for the electronic meter and 8.9% for the laboratory assay. The overall sensitivity and specificity obtained were 80.3 and 95.1%, respectively, when BHB values were ≥1.2 mmol/L. Results indicate that the BHBCheck meter can be used as a reliable and rapid postpartum diagnostic test to detect hyperketonemia in field conditions.