Background Disease-related malnutrition affects 20-50% of hospital inpatients. Nevertheless, only 5-50% of malnourished patients receive nutritional support. It has several consequences for hospitals. One of the most important is the increase in health costs, estimated at 20-60%. However, detailed data on the financial outcomes of malnourished patients are usually less available than results from malnutrition screening tools.

Purpose This study's main objective was to estimate the increased costs due to malnutrition in hospitals. Secondary goals were to calculate the prevalence of malnutrition in a tertiary care hospital and to study the relationship between malnutrition, disease, the age of the patient and the length of hospital stay.

Materials and methods A retrospective observational study was performed between March and May 2011. Inpatients from two medical wards were selected at the moment of discharge. The following variables were collected: demographic and anthropometric data, length of stay, number of medical tests performed, number of drugs administered, nutritional treatment and costs of the stay. Nutritional screening was performed using the Short Nutritional Assessment Questionnaire (SNAQ) and Nutritional Risk Screening 2002 (NRS-2002). Statistics were analysed using SPSS.

Results 58 patients were recruited: 67.2% men, 69% with chronic diseases with acute deterioration, average age 70.3 and length of stay 15.7 days. Prevalence of malnutrition was 46.6% (32.8% with frank malnutrition and 13.8% at risk of malnutrition). Only 1.7% of inpatients received nutritional support. The relation between nutritional status and length of hospital stay, kind of pathology, number of medical tests performed, number of drugs administered and stay costs were statistically significant.

Conclusions The prevalence of malnutrition is high in hospital inpatients. Malnourished patients have a longer stay in hospital than well-nourished patients. Nutritional status is influenced by several factors such as gender and disease severity. Inadequate nutritional status is associated with increased resource utilisation, leading to a significant increase in stay costs.