Closeup of hand filling glass with water at kitchen sink.The human body is comprised largely of water. If you lose more fluids than you take in, you can become dehydrated. This means there are not enough fluids in your body for it to function right. Mild dehydration can cause weakness, confusion, or muscle cramps. In extreme cases, it can lead to brain damage and even death. That's why prompt treatment is crucial.

Risk factors

Anyone can become dehydrated. But infants, children, and older adults are at greatest risk. You are most likely to lose fluids with severe vomiting, diarrhea, or a fever. Exercising or working hard—especially in hot weather—can also cause excess fluid loss.

What to do

Drinking liquids is the best way to prevent dehydration. Water is best, but juice or frozen pops can also help. For adults, don't use liquids that contain caffeine or alcohol to rehydrate. Your doctor may suggest electrolyte solutions for sick infants and young children.

When to go to the emergency room (ER)

Go to an ER right away for these symptoms:


  • Very dark urine and little urine output

  • Dizziness, weakness, confusion, fainting


  • Sunken eyes

  • Little or no urine output (for infants, no wet diaper in 8 hours)

  • Very dark urine

  • Skin that doesn't bounce back quickly when pinched

  • Crying without tears

  • Lethargy, decreased activity, or increased sleepiness

What to expect in the emergency room

Your blood pressure, temperature, and heart rate will be checked. You may have blood or urine tests. The main treatment for dehydration is fluids. You may be given these to drink. Or, you may receive them through a vein in your arm. You also may be treated for diarrhea, vomiting, or a high fever.