Dehydration means your body does not have enough fluid. This may be because you haven't drunk enough fluid to replace the fluids you have lost, such as when sweating or in your wee (urine). If dehydration isn't treated it can get worse and become a serious problem.
This is a companion discussion topic for the original article at https://patient.info/digestive-health/nausea-and-vomiting/dehydration