A common finding in patients admitted to an Intensive Care Unit (ICU) is hyperglycemia without prior history of diabetes. This increase in blood glucose is considered a negative prognostic factor for patients in the ICU. Hence, we performed a retrospective cohort study in patients admitted at the ICU of the National Institute of Respiratory Diseases (INER) in a 7-month period; we collected data about their blood glucose concentration during their stay at the ICU. We gathered the available medical records of 30 patients out of 58 admitted to the ICU. Among the 30 patients, 21 patients survived (70%) and 9 patients with community-acquired pneumonia (CAP) died (30%). The 21 surviving patients included 17 patients with acute respiratory distress secondary to CAP and 4 patients with asthmatic crisis upon admission to the ICU. After admission, all patients progressed to sepsis and showed an increase in blood glucose. We detected higher glucose concentrations in deceased patients (147 mg/dl ± 4.23), as compared to surviving patients (129 mg/dl ± 2.17) (P < 0.001). In addition, the percentage of lymphocytes was lower in deceased patients than that in surviving patients (5.7 vs. 11.8%, P < 0.001), whereas percentage of neutrophils was elevated in the deceased patients (90.7 vs. 80.9%, P < 0.001). It is therefore important to measure continuously glucose concentrations, as well as the numbers of neutrophils and lymphocytes in critically ill patients with hyperglycemia. Such a simple monitoring plan may prevent fatal complications in patients admitted to ICU.