Symptoms of early or mild dehydration include thirst, flushed face, dry skin, warm skin, small amounts of dark yellow urine, lightheadedness, dizziness that is worse when you stand up, weakness, cramping, having few tears, headache, a lack of energy, and dry mouth.

When dehydration is moderate to severe, other symptoms are low blood pressure, fainting, severe muscle cramping, convulsions, a bloated feeling, sunken eyes, and rapid breathing.