Dehydration and Rehydration in Children 

Baby drinking water.

Dehydration happens when a person loses more fluids than he or she takes in. The human body is made up largely of water, so you need the right balance of fluids in your system for good health. Large amounts of fluids can be lost through fever, diarrhea, vomiting, or sweating. Dehydration happens very quickly in infants and small children. This is because they don’t have as much fluid to spare. Dehydration can quickly become very serious. Rehydration is the important way of returning those fluids back to the body. This restores normal functioning.

Signs of dehydration

Watch for these signs of dehydration. This is especially true if your child has a fever or diarrhea, or is vomiting:

  • Dry mouth or extreme thirst

  • Fewer than 6 wet diapers a day for infants, or less frequent urination in older children

  • Fussy or agitated behavior

  • Looking or acting very tired or weak, or increased sleeping

Treating dehydration

If you suspect dehydration, call your healthcare provider. You can treat mild dehydration at home by doing the following:

  • Keep track of how much fluid your child drinks and how often he or she urinates.

  • Breastfeed or bottle-feed a sick infant more often, but for shorter periods of time.

  • For vomiting or diarrhea, give your child 1 to 2 teaspoons of an oral rehydration solution (ORS) every 10 minutes. Continue until your child can drink larger amounts of fluid without vomiting or passing stool.

  • Avoid soft drinks, tea, juice, broth, or sports drinks such as electrolyte solutions. These may make symptoms worse.

  • Don't use medicines for vomiting and diarrhea, unless your healthcare provider tells you to.

  • If your child has a hard time keeping fluids down and becomes very dehydrated, your healthcare provider may decide to treat him or her in a hospital. There, a healthcare provider can make your child comfortable. Your child will be given fluids and nourishment by mouth or through an intravenous (IV) line. Medicine may be given to stop the vomiting and allow your child to drink enough fluid to stay hydrated.

When to seek medical care

Get medical care right away if your child:

  • Has fever (see Fever and children, below)

  • Is an infant vomiting all feeds (not just spitting up)

  • Hasn’t urinated for 6 hours or more, or has dark or strong-smelling urine

  • Can’t drink even small amounts of liquid without vomiting

  • Can't be soothed or is very irritable or restless

  • Seems unusually drowsy, listless, weak, or limp

  • Has muscle cramps

  • Has dry, wrinkled, or pasty-looking skin, sunken-looking eyes, a very dry or sticky mouth, or cracked lips

Fever and children

Always use a digital thermometer to check your child’s temperature. Never use a mercury thermometer.

For infants and toddlers, be sure to use a rectal thermometer correctly. A rectal thermometer may accidentally poke a hole in (perforate) the rectum. It may also pass on germs from the stool. Always follow the product maker’s directions for proper use. If you don’t feel comfortable taking a rectal temperature, use another method. When you talk to your child’s healthcare provider, tell him or her which method you used to take your child’s temperature.

Here are guidelines for fever temperature. Ear temperatures aren’t accurate before 6 months of age. Don’t take an oral temperature until your child is at least 4 years old.

Infant under 3 months old:

  • Ask your child’s healthcare provider how you should take the temperature.

  • Rectal or forehead (temporal artery) temperature of 100.4°F (38°C) or higher, or as directed by the provider

  • Armpit temperature of 99°F (37.2°C) or higher, or as directed by the provider

Child age 3 to 36 months:

  • Rectal, forehead (temporal artery), or ear temperature of 102°F (38.9°C) or higher, or as directed by the provider

  • Armpit temperature of 101°F (38.3°C) or higher, or as directed by the provider

Child of any age:

  • Repeated temperature of 104°F (40°C) or higher, or as directed by the provider

  • Fever that lasts more than 24 hours in a child under 2 years old. Or a fever that lasts for 3 days in a child 2 years or older.

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