The promotion of healthy eating and physical activity is part of the prevention and treatment of diseases in modern medicine. The aim of our research was to study the clinical principles in compiling a diet for patients who are already on drug therapy for a diagnosed disease, guided by the principle of healthy eating. Material and method: we conducted a study motivated by personal experiences on the interaction of drugs and nutrients in diets prescribed for healthy eating in certain diseases, with a special aspect of anticoagulant therapy. The basic principle of the protocol should include the underlying disease, medications for the same, past diseases with a deficit of certain organs in function and an assessment of the existing diet and supplements to prevent drug interactions. Results: More than 30% of people take supplements on their own. Knowledge of the interaction of drugs with supplements and nutrients with medications is of crucial importance for preventing the consequences of their synergistic or antagonistic interaction, of which bleeding is the key and most dangerous. Discussion: Modern management of patients in the perioperative period is crucial to avoid bleeding or thrombosis. The medical team takes into account all possible risks, based on the clinical examination, blood laboratory and possible drug interactions, but there is not always available data on the patients' supplementary therapy, which may be a risk. Conclusion: When recommending the consumption of supplements and diet for a given disease, the possible interaction of the drug and the condition of the organs that may be damaged should be taken into account.