DEHYDRATION - A condition of decreased body fluid. Common in cases of excess diarrhea, vomiting, or poor fluid intake. Some medications (diuretics) can also cause dehydration. Features include decreased urine output, thirst, dry mouth, dry skin, rapid heart rate, and lightheadedness (particularly with standing). More severe cases may include confusion or a decreased level of consciousness. Features of dehydration in infants include decreased urine output, lethargy, listlessness, dry mouth and skin, and failure to cry tears.