What is dehydration?

Dehydration is when your body loses more fluids than it gets in from drinking fluids and eating foods.

Did you know that babies, children and elderly people have a higher chance of becoming dehydrated? Even more reason to be aware of the various causes and signs of dehydration, so you can help prevent it from happening and know to speak to a GP or Pharmacist if you think your child is dehydrated.

What causes dehydration?

There are quite a few things that can cause dehydration in babies.

Being ill and having symptoms like a fever, a sore throat that makes it hard to swallow fluids, and gastroenteritis can lead to dehydration if your baby doesn't want to drink as much as usual because they are not feeling well. Hotter climates and being more physically active can also cause dehydration. Dehydration is usually caused by not drinking enough fluid to replace what we lose.


Do you have to change nappies more often than usual? Diarrhoea can cause dehydration in babies. You need to take extra precautions to make sure they stay hydrated if you notice that their stool is watery and they have bowel movements more often.


The more your baby vomits, the higher their chances are of becoming dehydrated. Vomiting not only leads to fluid loss, but a loss of salts too, which are crucial for the right balance of body fluids.

Overheating and sweating excessively.

Another way your baby can lose fluids and become dehydrated is through sweating excessively.

What can make babies overheat and sweat too much?

  • Clothing that's too warm
  • Clothes made from fabric that's not very breathable
  • Blankets that are too thick
  • High temperatures  

When outside on a really sunny day, try to protect baby from the sun's rays and make sure s/he stays as cool as possible. The shade is your friend. 

Low breast milk supply

If mum isn't producing enough breast milk, the baby might not be able to get all the nutrients and hydration they need. 

If you’re breastfeeding, take care to monitor your breast milk supply to ensure your little one is getting enough. You can speak to a midwife, health visitor and GP for advice if you are worried about your milk supply.

Things that can affect breast milk supply include mum’s fluid intake, stress & getting skin-to-skin contact with the baby and being away from your baby without pumping.

Trouble latching on and drinking 

You know, we know it - breastfeeding can be hard work. It could be that you’re providing enough milk, but your baby could be struggling to latch on properly during breastfeeding sessions.

It’s best to speak to your GP, midwife or health visitor for advice on how to help.

Having a fever

A fever can cause fluid loss by causing sweating, which can lead to dehydration. If your baby has a fever, you can give them paracetamol if they’re older than 2 months, or if they’re older than 3 months and weigh more than 5kg, you can give them ibuprofen for the relief of fever.

Signs and symptoms of dehydration in babies 

Here are some of the symptoms and signs of dehydration in babies:

  • Very few or no tears when crying
  • Drier nappies
  • Pee that’s a dark colour
  • Blotches on the hands and feet
  • Sleeping more than normally (sleeping too much for their age)
  • Dry and wrinkled skin
  • A dry mouth
  • Being drowsy and tired
  • A sunken fontanelle (soft spot on their head)
  • Breathing rapidly and having a fast heart rate
  • Being constipated and having fewer or hard bowel movements

If you notice any of these signs of dehydration in your baby, we recommend that you take your baby to the GP or A&E straight away. 

When to seek help

A blocked nose will usually pass by itself, but speak to your GP, or call NHS 111 if your baby:

  • Has to work hard in order to breathe
  • Feel cold or hot when you touch them
  • Cannot or don’t want to feed
  • Don’t have as many dirty or wet nappies as they usually do
  • Isn’t getting better
  • Has a blocked nose all the time, even when they don’t seem ill otherwise

When should you call 999 or go to A&E?

  • If your baby has pauses in their breathing or stops breathing
  • If they have trouble breathing
  • Have a convulsion or fit
  • If their lips, tongue and skin are abnormal in colour, usually pale, blue or purple
  • If they cannot wake up or wake up with a lot of difficulty
  • If they are breathing very rapidly even when not crying or upset and when they’re resting
  • If they look very unwell

As a parent, it's always good to trust your instincts when it comes to your child. If you sense there is an emergency, call 999.

All information presented on these web pages is not meant to diagnose or prescribe. In all health matters for further information or medical advice, please speak to your GP or a Pharmacist.