Maintaining the fluid balance requires complex crosstalk within the neural circuits and endocrine systems through the brain-body axis. Previous research focused on the thirst-driving pathways in the brain. Recent studies have shed more light on the role of postingestive feed-forward modulation mediated by peripheral signals. Advances in technology have unveiled the genetic profiles of the underlying circuits, enabling more precise interventions in future translational research. Despite the prevalence of fluid balance dysregulation in modern life, its health relevance remains underappreciated. In this review, we summarize the recent major findings in the field and describe common fluid-related disorders.