How can I tell if I'm dehydrated?

Studies show approximately 75% of Americans regularly experience mild to moderate dehydration. Some signs to look out for include dizziness, headaches, muscle cramps, fatigue, dry skin, brain fog, extreme thirst, dry mouth and decreased urine output. In children, you might notice sunken eyes. And in infants, look for a sunken fontanel (the soft spot on the top of a baby's head) and an absence of tears.