We are all familiar with the drawbacks of dehydration, but we rarely hear about the harmful effects of overhydration. It is known that excess fluid accumulation can lead to dangerously low sodium levels in the blood or hyponatremia – a life-threatening condition that can result in brain swelling. Similarly, more is known about the mechanisms in the body that detect and drive thirst while little is known about how the brain detects a state of overhydration.