Outcomes of drug and nutrient interactions may be beneficial or adverse. Risk assessment for drug and nutrient interactions requires knowledge of the drug(s) being used; their pharmacology, indication and side effects; the age, disease and organ function and nutritional status of the patient receiving these drugs, and the regimen including the drug list, dose, duration and frequency of drug administration, the diet, nutrient supplements and the timing of drug administration in relation to food or supplement use. Intervention to prevent the occurrence of a drug and nutrient interaction necessitates weighing the advantages against the disadvantages of changing drug and diet orders.