Objective. The objective of our study was to assess the influence of hematocrit (HCT), partial pressure of oxygen (PO2), and blood glucose level upon results obtained with three different blood glucose reagent strip tests used in conjunction with the appropriate meter: BM-Test 1-44, BM-Accutest, and Satellite G. Methods. Our study was designed as a consecutive sample study of patients undergoing coronary artery surgery. The setting was the hospital theater and intensive care unit. We conducted blood analysis for HCT, PO2 and blood glucose on 20 consecutive patients undergoing coronary artery surgery using three blood glucose reagent strip testing systems and a laboratory analysis of plasma glucose. Results, All three blood glucose reagent strip tests showed a significant bias when compared with plasma glucose: BM-Test 1-44, 0.89 mmol/L; BM-Accutest, -1.27 mmol/L; Satellite G, 0.75 mmol/L (p < 0.05). The error found when using the Satellite G system was worse than that of either of the other two systems. Results obtained with the BM-Accutest strips were unaffected by PO2 (p = 0.745). Blood glucose value and HCT both had an influence on the results of all three blood glucose strip systems. Conclusions, Caution must be taken when using reagent strip systems in the operating room or intensive care setting because, of the three systems tested, all showed a significant bias, all were influenced by blood glucose level and HCT, and only the BM-Accutest reagent strips used with the Accutrend meter was unaffected by PO2.