For disturbances of consciousness such as syncope, coma, stupor, or delirium, there is not always an obvious explanation like stroke, trauma, or neoplastic causes. More complex conditions, known as encephalopathies, can lie behind these disturbances. They present a particularly challenging topic both diagnostically and therapeutically—especially for neurologists, psychiatrists, and intensive care physicians. Encephalopathies manifest as neurological and psychiatric dysfunctions, with causes that are not solely located in the brain. Diseases of various organs or organ systems can be causative and produce similar clinical pictures. This complicates the diagnostic process and necessitates a comprehensive exclusion procedure. The practical guide systematically covers the complex topic of encephalopathies, starting from the common and diverse symptom of disturbances of consciousness.