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What is dehydration and how can you tell if you're dehydrated?

21 October 2025
Female runner drinking water from a bottle

Did you know that 50 to 80% of the human body is water? And that we get about 75% of that water from drinking fluids (the rest comes from our food)?

But for some people, it can be hard to drink the recommended eight to 10 cups of fluid each day. And if you don’t get enough liquids in your body, especially during summer, it could lead to dehydration. 

What is dehydration? 

Dehydration occurs when you don’t have enough fluids in your body. When you’re dehydrated, your body might not function the way it’s meant to. 

What are the signs of dehydration in adults? 

There are a lot of signs of dehydration, so it can be quite easy to spot if you aren’t drinking enough fluids. But there are two types of dehydration: mild to moderate or severe dehydration. Both types of dehydration have different sets of symptoms.

Some of the signs of mild to moderate dehydration include: 

  • Being thirsty or having a dry mouth, lips or tongue 

  • Feeling dizzy or light-headed, especially when standing up 

  • You have a headache or fever 

  • You have dark urine or urinate less than usual. 

And if you’re experiencing severe dehydration, then you might: 

  • Feel very thirsty 

  • Breathe very quicky and have a fast heart rate 

  • Have low blood pressure and cold hands and feet 

  • Feel tired, confused or irritable 

  • Have sunken eyes, which is when your eyes appear dark or hollow. 

What are the signs of dehydration in children? 

The symptoms of dehydration in children are pretty much the same as the signs of dehydration in adults. But for babies and toddlers, keep an eye on their nappies. If their nappies are not as wet as usual or as frequently, it might be a sign they’re not getting enough to drink. 

What causes dehydration? 

There are different reasons you might become dehydrated during the day. You (or someone else) might be dehydrated from: 

  • Not drinking enough water 

  • Vomiting, diarrhoea or a fever 

  • Drinking too much alcohol at once 

  • Doing intense exercise, especially when it’s very hot 

  • Taking certain medicines or having diabetes. 

What should you do if you’re dehydrated? 

First of all, don’t panic. Being dehydrated from time-to-time happens to everyone. The first step you should take is moving to a cool, shady place and loosening any tight clothing you’re wearing. Or, if you’re at home, you can remove unnecessary clothing to help regulate your body temperature. 

While it might be tempting to scull a two-litre water bottle, you should have small (but regular) sips of cool water. It’s also important to avoid having drinks that could make your dehydration worse, like sugary drinks, caffeine and alcohol. 

How to avoid dehydration 

Avoiding dehydration can be quite easy if you follow these simple hydration tips: 

  • Keep a water bottle with you and take regular sips from it throughout the day 

  • If you’re dehydrated from a summer workout, consider drinking electrolytes 

  • Flavour your water with lemon, berries or mint 

  • Have a glass of water on the dining table (when you eat) or at your desk (when you work) 

  • Try herbal teas or sparkling water if you want a bit of fluid variation in your day 

  • Make some healthy smoothies or juices for a tasty and refreshing meal or snack. 

Stay hydrated and healthy with nib 

If you’re an nib member, you can access heaps of discounts to help you stay healthy through nib Rewards. Receive great discounts across a range of brands and services, like meal-kits and activewear, to support your journey to good health. Plus, you might be able to snag a nifty water bottle at a discount to help you stay hydrated. 

On top of all that goodness, you can do a quick and easy HealthCheck to get a better understanding of where you’re at with your health. It takes less than 10 minutes and it can give you tailored insights on how to improve your wellbeing, even if it means drinking more water.