Keeping your child hydrated is one of the simplest ways to maintain health and prevent medical problems. But how do you know how much fluid your child needs, especially if your child does not drink fluids orally or has difficulty associating thirst with drinking?

The easiest way to make sure your child is hydrated is to keep track of how much urine she is producing, with babies having at minimum 4-8 wet diapers a day, and older children urinating at least 4-8 times a day.

If you are concerned about your child’s fluid intake, you may want to calculate how much liquid he should be receiving based on his size. The simplest method for determining fluid needs is the Holliday-Segar Calculation. This method bases fluid requirements on the child’s weight, using the average requirement of 100 mL water for each 100 calories metabolized.

While this calculation is widely used, it has been called into question recently. First and foremost, the fluid requirements in this calculation were determined based on intravenous administration and not oral or enteral intake. They are also not valid for newborns, children who are overweight, or older children nearing full adult size.

Children who are vomiting, have diarrhea, are sweating excessively, or who are exposed to extremely high temperatures, require even more fluids than listed above. Moreover, children with medical problems that cause them to metabolize calories at a slower or faster rate made need more or less fluids. For example, a child who is inactive due to cerebral palsy may require less fluids, while a child who has diabetes may require more fluids. It is important to talk to your child’s doctor or dietician about your child’s particular fluid needs, based on her age, size, activity level, and medical history.

Holliday-Segar Method for Calculating Fluid Requirements
Body Weight of Child Water/Free Liquids Required
5 kg - 500 mL 

6 kg - 600 mL 

7 kg - 700 mL
8 kg - 800 mL
9 kg - 900 mL
10 kg -1000 mL
11 kg - 1100 mL
13 kg - 1150 mL
14 kg -1200 mL
15 kg -1250 mL
16 kg - 1300 mL
17 kg -1350 mL
18 kg -1400 mL
19 kg -1450 mL
20 kg -1500 mL
25 kg -1600 mL
30 kg -1700 mL
35 kg -1800 mL
40 kg -1900 mL

What counts as a fluid?
For young babies, formula or breastmilk is usually adequate since infant formulas and breastmilk (with 20 calories per ounce) are typically 95% free water. Water and juice can be introduced around six months of age. Children over a year of age who eat regular diets can get their fluids from a variety of sources. Water is of course the best option, but clear liquids such as juice, gatorade, and even popsicles are a good second choice. Milk, fresh fruits and vegetables, and other “wet” foods also will provide ample fluids to the body.

As long as your child is eating a wide variety of foods and drinking the appropriate amount of water, milk, and juice, she should stay wellhydrated. Children on special diets or who are tube fed require more careful monitoring of fluid intake. Many of these children suffer from chronic low-level dehydration, which can
contribute to worsening reflux, constipation, stomach discomfort, and even irritability or pain.

Paediatric formulas (30 calories per ounce) are typically 85% free water, and can serve as the main source of fluids for most children. It is important, however, that children who are formula-fed still receive some free water. Free water is extremely helpful to combat many gastrointestinal ailments, ranging from reflux to constipation and other motility issues.

Free water should be offered to children frequently throughout the day, especially if the child does not sense or indicate thirst well. Children who are tube fed should receive water flushes throughout the day, and water boluses several times a day if tolerated.

Another option, particularly for children weaning off feeding tubes, is to give water overnight while the child is sleeping. 

It is important to be able to recognize the signs of dehydration in a child. 
Mild dehydration often is asymptomatic, with thirst and yellow urine the only signs. More serious dehydration leads to dryness in the skin, lips, and tongue, irritability, and decreased urine output. Severe dehydration, which requires immediate medical attention, causes lethargy, clammy skin, a parched mouth, and a fast and weak pulse.

Signs of Mild Dehydration
Skin: Normal
Lips/tongue: Moist
Eyes: Normal
Tears: Present
Fontanelle: Flat
Mood: Consolable
Pulse: Normal
Urine Output: Normal, Yellow.

Signs of Moderate Dehydration
Skin: Dry
Lips/tongue: Dry
Eyes: Deep set
Tears: Reduced
Fontanelle: Soft
Mood: Irritable
Pulse: Increased rate, weak
Urine Output: Decreased, Dark yellow.

Signs of Severe Dehydration
Skin: Dry
Lips/tongue: Dry
Eyes: Deep set
Tears: Reduced
Fontanelle: Soft
Mood: Irritable
Pulse: Increased rate, weak
Urine Output: Decreased, Dark yellow.

It is definitely possible to drink too much water. Overloading the body with fluids can cause water intoxication or hyponatremia, an imbalance between water and sodium in the blood plasma. Fortunately, this is a very uncommon occurrence in children. While you and your children enjoy the summer heat, make sure that you all stay well hydrated!

Adapted from Brian Stone, “Fluids and Electrolytes,” in The Harriet Lane Handbook, 17th Edition, edited
by Jason Robertson and Nicole Shilkofski. Philadelphia: Elsevier Mosby, 2005, p. 298