Accurate cow-side blood β-hydroxybutyrate (BHB) detection meters are valuable tools for minimally invasive, cow-side diagnosis of hyperketonemia. The objective of this study was to compare the blood BHB measured in whole blood by the BHBCheck meter (PortaCheck, Moorestown, NJ) to the gold standard of BHB measured in serum or plasma by colorimetric assay. Samples (n = 445) were collected from postpartum Holstein cows (n = 87 cows) enrolled in 1 of 2 experiments (exp) with different sampling schedules (exp 1: n = 47 cows, 72 samples; exp 2: n = 40 cows, 373 samples). In both exp, whole blood samples were collected from the coccygeal vessels after morning milking, before morning feeding, and used immediately for BHB quantification via the BHBCheck meter and the Precision Xtra meter (Abbott Laboratories, Abbott Park, IL) as a comparison to another cow-side BHB meter that is widely accepted. Simultaneously, blood was collected into evacuated tubes containing no additive (exp 1) or potassium oxalate/sodium fluoride (exp 2) which were centrifuged for serum or plasma separation and stored at −20°C for subsequent analysis. Quantification of BHB concentration was via the BHB LiquiColor Assay (Stanbio; certified for serum and plasma) and analyzed with the BioTek spectrophotometer. Data were analyzed by Reg and Freq procedures of SAS 9.4. Average parity of the cows was 2.4 and average DIM at sampling was 14.8 d. The prevalence of hyperketonemia (BHB ≥1.2 mmol) was 23.1, 27.9, 30.4% as determined by the laboratory assay, BHBCheck meter, and Precision Xtra meter, respectively. Coefficient of determination for BHBCheck meter BHB concentration compared with the colorimetric assay concentrations was R² = 0.88 with a sensitivity of 91.2%, and specificity of 91.1%. Coefficient of determination, sensitivity, and specificity of the Precision Xtra meter concentrations were 0.90, 98.0%, and 89.9%, respectively. The BHBCheck meter exhibited reliable sensitivity and specificity for use as a valuable cow-side diagnostic test for hyperketonemia in dairy cows.