OBJECTIVES: Provision of nutritional support (NS) can improve disease outcome and shorten hospital length of stay. NS, often prescribed by medical doctors, requires adequate clinical nutrition (CN) expertise. The aim of this study was to investigate self-perceived and actual CN knowledge among medical doctors in Greece.METHODS: Internal medicine physicians and surgical specialties (residents and specialized) were asked to self-evaluate their CN expertise, via a seven-item questionnaire and to complete a 20-question multiple-choice test on CN topics, with the aim of evaluating their actual CN knowledge. Participants were discouraged from accessing literature/information during the completion of either questionnaire.RESULTS: Of 182 invited medical doctors, 115 (50.4% surgical specialties) participated in the study (63.2% response rate). The majority of participants (65.2%) demonstrated inadequate CN knowledge, with 30.4% of those scoring low having a high self-perception of their CN expertise. Comparison of perceived and actual CN knowledge revealed that only 56.5% of the participants estimated their knowledge correctly. Those who had participated in CN continuous medical education courses demonstrated increased related expertise (P = 0.002).CONCLUSIONS: Medical doctors in Greece demonstrate low knowledge of fundamental CN principles, jeopardizing the provision of high-quality and efficient NS. Most importantly, the majority of participants overestimated their CN knowledge and prescribe artificial nutrition or participate in related decision making. Physicians' CN knowledge should be enhanced accordingly, either by attending CN modules during their studies, by participating in basic and advanced courses or CN-specific continuous medical education, or both.