Lithium-induced diabetes insipidus occurs in up to one third of patients on long-term therapy. It usually manifests during the treatment course, often with preceding signs or symptoms. We wish to highlight a case in which diabetes insipidus developed many days after cessation of long-term lithium therapy. We seek to explain this delayed onset by a discussion of the molecular and genetic changes underlying the pathogenesis of lithium-induced nephrogenic diabetes insipidus.