• Dry or sticky mouth
• Low or no urine output; concentrated urine appears dark yellow
• Not producing tears
• Sunken eyes
• Markedly sunken fontanelles (the soft spot on the top of the head) in an infant
• Lethargic or comatose (with severe dehydration)

In addition to the symptoms of actual dehydration, you may also have vomiting, diarrhea, or the feeling that you "can't keep anything down," all of which could be causing the dehydration.

A physical examination may also show signs of:

• Low blood pressure
• Blood pressure that drops when you go from lying down to standing
• Rapid heart rate
• Poor skin turgor -- the skin may lack its normal elasticity and sag back into position slowly when pinched up into a fold by the doctor; normally, skin springs right back into position
• Delayed capillary refill
• Shock

Tests include:

• Blood chemistries (to check electrolytes, especially sodium, potassium, and bicarbonate levels)
• Urine specific gravity (a high specific gravity indicates significant dehydration)
• BUN (blood urea nitrogen -- may be elevated with dehydration)
• Creatinine (may be elevated with dehydration)
• Complete blood count (CBC) to look for signs of concentrated blood

Other tests may be done to determine the specific cause of the dehydration (for example, a blood sugar to check for diabetes).