© 2015, Hacettepe University, Faculty of Pharmacy. All rights reserved.Around the globe, life expectancy is ascending and geriatric population is rapidly increasing. Frequency of several diseases is rising with age and this brings along polypharmacy. Drug-nutrient and drug-disease interactions are often seen in elderly who apply polypharmacy. While nutrients can change the biotransformation and efficacy of drugs, drugs can also alter the biotransformation and efficacy of nutrients. On the other hand, existing disease along with drugs can worsen the course of the disease or drug use can increase the possibility of disease emergence. This review will evaluate drug-nutrient and drug-disease interactions from a toxicological perspective.