(HealthDay News) -- Dehydration occurs when the body doesn't have enough fluids, either because it's lost too many fluids, a person hasn't drunk enough fluids, or both.

The U.S. National Library of Medicine lists these common warning signs of significant dehydration:

• Not being able to urinate, or urinating very little.
• Urine that is very concentrated and dark yellow in color.
• Not being able to produce tears.
• Sunken eyes.
• In infants, the soft spot on the head is significantly sunken.
• Lethargy, dizziness or lightheadedness.

Dehydration should not be ignored, and you should see a doctor immediately if you or your child has any of these symptoms.