Water balance or fluid intake-output balance, is the comparison between the fluid volume that is provided or ingested, that is, the volume of intravenous saline solutions, diet, etc., and volume that leaves the body to the exterior: urine, sweat, stools, etc. This balance should be maintained, that is, the volume provided and excreted should be practically equal. If there is an imbalance, appropriate adjustments should be made. To estimate this balance and ensure the value is real, the amount ingested and excreted by the patient should be strictly monitored.