Among the substances such as caffeine, alcohol, and nicotine, the latter two undoubtedly pose significant risks to health. Nevertheless, they are regularly consumed by many people. Their effects on the entire organism are diverse, including interactions with medications. The authors compile expertise on alcohol, caffeine, and nicotine for daily consultations: - Effects on bodily functions and particularly sensitive organs - Gender and age-related differences - Risks and subsequent health issues - Dependence, including therapy and prevention - Interactions with medications such as analgesics, antibiotics, antidiabetics, anticoagulants, and psychotropic drugs - Information on legal aspects in professional and traffic contexts, as well as references to counseling services. Images and tables facilitate an overview of symptoms and specific aspects.