Dehydration means your body does not have as much water and fluids as it should. Dehydration can be caused by losing too much fluid, not drinking enough water or fluids, or both. Vomiting and diarrhea are common causes.

Infants and children are more susceptible to dehydration than adults because of their smaller body weights and higher turnover of water and electrolytes. The elderly and those with illnesses are also at higher risk.

Dehydration is classified as mild, moderate, or severe based on how much of the body's fluid is lost or not replenished. When severe, dehydration is a life-threatening emergency.

Your body may lose too much fluids from:

• Vomiting or diarrhea
• Excessive urine output, such as with uncontrolled diabetes or diuretic use
• Excessive sweating (for example, from exercise)
• Fever

• Nausea
• Loss of appetite due to illness
• Sore throat or mouth sores

Dehydration in sick children is often a combination of both -- refusing to eat or drink anything while also losing fluid from vomiting, diarrhea, or fever.

• 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)

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

• 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