Objectives: To determine the effect of the enteral nutrition algorithm on nutritional support in critically ill medical patients. Methods: The quasi-experimental study was conducted at a medical Intensive Care Unit of a university hospital in central Anatolia region in Turkey from June to December 2008. The patients were divided into two equal groups: the historical group was fed in routine clinical applications, while the study group was fed according to the enteral nutritional algorithm. Prior to collecting data, nurses were trained interactively about enteral nutrition and the nutritional support algorithm. The nutrition of the study group was directed by the nurses. Data were recorded during 3 days of care. SPSS 22 was used for statistical analysis. Results: The 40 patients in the study were divided into two equal groups of 20(50%) each. The energy intake of study group was 62% of the prescribed energy requirement on the 1st, 68.5% on the 2nd and 63% on the 3rd day, whereas in the historical group 38%, 56.5% and 60% of the prescribed energy requirement were met. The consumed energy of the historical group on the 1st 2nd and 3rd day was significantly different (p=0.020). In the study group, serum total protein and albumin levels decreased significantly (p0.05).Conclusion: The use of standard algorithms for enteral nutrition may be an effective way to meet the nutritional requirements of patients.