Hydration for children: how much and what should they drink?

Why hydration is important for children

Water is a natural part of how the body functions. Children get fluids not only from drinking, but also from milk, soups, fruit, vegetables and other foods. Fluid needs therefore vary from day to day: they increase in hot weather, during sports and active play, in overheated rooms, and with fever, vomiting or diarrhoea.

Young children can easily become absorbed in play and may not signal thirst in time. A baby cannot say that they are thirsty either. The parent’s role is therefore not to make a child drink an exact amount, but to offer a suitable drink regularly and pay attention to their overall wellbeing, activity and urination.

A good daily routine is to keep water within reach: at home during meals and play, on walks and at nursery. Offer a few sips after waking up, with meals, before going outside and after physical activity. On warm days or during intense activity, offer it more often and in smaller amounts.

Remember that crying, irritability and tiredness can have many causes. On their own, they do not reliably indicate a lack of fluids. It is more useful to consider the overall picture and whether the child is drinking and urinating roughly as usual.

Hydration by age: approximate amounts

Take the following amounts as an approximate daily total water intake, meaning fluids from drinks as well as water contained in food. An individual child’s needs may be higher or lower depending on the weather, activity, diet and health.

• Children up to around 6 months: if exclusively breastfed, they usually do not need additional water; they get the necessary fluids from breast milk. With formula feeding, follow the preparation instructions on the packaging and your paediatrician’s advice. Do not give a baby water instead of a milk feed without consulting a professional.
• Approximately 6 to 12 months: alongside milk and complementary foods, you can offer small amounts of plain water from a cup. Total water intake is usually around 800 to 1,000 ml per day, including milk and food.
• 1 to 2 years: approximately 1,100 to 1,200 ml per day in total.
• 2 to 3 years: approximately 1,300 ml per day in total.
• 4 to 8 years: approximately 1,600 ml per day in total.

For older schoolchildren, needs continue to increase, with sport, ambient temperature and the child’s size playing an important role. In case of health problems, kidney or heart disease, or a recommended fluid restriction, always follow your doctor’s advice.

Hydration calculator: the number is only a guide

In practice, a weight-based rule is sometimes used to estimate the total daily fluid needs of healthy children. For the first 10 kg of body weight, the estimate is approximately 100 ml per kilogram per day; for the next 10 kg, around 50 ml per kilogram; and above 20 kg, around 20 ml per kilogram. This is the total fluid from all sources, not the amount of plain water a child must drink.

Example: for a child weighing 12 kg, the approximate calculation is 1,100 ml per day: 1,000 ml for the first 10 kg and a further 100 ml for 2 kg. However, some of this amount will come from soup, fruit, vegetables or milk.

This calculator is not intended to monitor every millilitre or persuade a child to drink excessively. Needs change in hot weather, during sport, with fever, vomiting or diarrhoea, and the calculation may not be sufficient. If you are unsure how much fluid is appropriate for your child, discuss it with your paediatrician.

Which fluids are suitable and which are best avoided

The best everyday drink for a toddler or older child is plain drinking water. It can be tap water if it is safe to drink in your household, or unflavoured bottled water suitable for children. Offer it in a favourite glass, bottle or cup – for some children, the way a drink is served is surprisingly important.

• Suitable: plain water, unsweetened weak fruit or herbal tea appropriate for the child’s age, or water flavoured with a piece of fruit for aroma and taste only.
• In moderation: milk is part of a child’s diet, but it should not replace regularly offering water. Pure fruit juice is not a substitute for water; even without added sugar, it contains natural sugars and is best offered only occasionally and in small amounts.
• Not as an everyday drink: sugary soft drinks, flavoured waters, iced teas, energy drinks and caffeinated beverages. They can unnecessarily encourage a preference for sweet flavours, and some contain substances unsuitable for children.

If your child refuses water, calmly offer small sips repeatedly and without pressure. Drinking together, having their own bottle, offering water with meals or after returning from the playground may help. Do not use a sweet drink as a reward for drinking water – the child may start associating it with something more valuable than ordinary hydration.

Dehydration in children: possible signs and when to call a doctor

When a child lacks fluids, they may be thirsty, have a dry mouth and lips, darker urine or urinate less often than usual. You may also notice unusual tiredness, lethargy, a headache, irritability or less interest in playing. In babies, fewer wet nappies, crying without tears or unusual sleepiness may be noticeable.

However, these signs can also be related to other conditions and should not be used to make a diagnosis at home. The risk of dehydration is particularly higher with vomiting, diarrhoea, fever, heavy sweating or when a child refuses to drink. In these situations, offer fluids more often and in small sips. With diarrhoea or vomiting, ask your paediatrician or pharmacist about the appropriate approach and whether an oral rehydration solution may be suitable.

Contact a doctor or emergency service without delay if the child cannot keep fluids down, urinates significantly less, is very sleepy, does not respond as usual, has difficulty breathing, appears seriously ill or you have any concern about their condition. For babies and young children, it is best to seek advice sooner if their condition worsens.

The best prevention is not a perfect calculation, but a calm routine: water available throughout the day, regular offers and extra attention in hot weather or during illness. In this way, you help your child build a habit that will stay with them into the future.