Objective: To establish the relationship between serum glucose and Scores of gravity: APACHE II / SAPS II as prognostic indicator of mortality in patients in intensive care unit. Materials and methods: Evaluation study of diagnostic and prognostic test that included 71 patients in critical clinical status of various etiologies; the probability of death was calculated using serum glucose levels regarding severity scores APACHE II and SAPS II. Data were obtained through interrogation and medical records subjected to statistical analysis. Results: 59% were male and 41% female. The highest frequency was 18 - 28 years old (25.31%). The cardiovascular and neurological liabilities were the most significant. Upon entering the critical care unit, glucose was higher than 180mg / dl in 33.73% of patients. The survival and mortality were 67.6% and 32.9%, respectively. The 60.8% of patients died had blood glucose > 180 mg / dl; while 39.13% had lower blood glucose. The glucose showed a sensitivity of 81% and specificity of 63.6% for identifying patients most and lower risk of death in ICU. Conclusion: Blood glucose> 180 mgs/dl was associated with increased mortality, although it was not specific to predict mortality. It can be a complementary test