Water is involved in almost everything your body does. It transports nutrients, removes waste products via your kidneys and helps maintain your body temperature. If you don’t drink enough for a while, your body will notice quite quickly. In this article, you’ll find out what happens if you don’t drink enough water, how to recognise dehydration from your urine and other signs, and roughly how much fluid you need each day.
What happens if you don’t drink enough water?
If you don’t drink enough, your body becomes slightly dehydrated. The first signs are thirst and a dry mouth, darker-coloured urine, headaches, tiredness and reduced concentration.
Exactly how much fluid you need depends on your age, the temperature, how much you exercise, what you eat and your state of health. On a hot day or whilst exercising, you lose more fluid through sweat, which means you’re more likely to become dehydrated. Mild dehydration is usually nothing to worry about: as soon as you start drinking enough again, your fluid balance will recover on its own. It’s mainly a sign that your body is asking to be rehydrated.
What are the first signs of dehydration?
The earliest signs of dehydration are thirst, a dry mouth and darker-coloured urine. You’ll often also notice that you’re going to the toilet less often.
Look out for these common signs:
- Thirst and a dry mouth or dry lips
- Dark, stronger-smelling urine and urinating less frequently
- Headache or light-headedness
- Tiredness, dizziness or slower reactions
- Difficulty concentrating or feeling irritable
Thirst is a useful but slow warning sign: it often only kicks in once you’re already a bit behind. That’s why it’s a good idea to drink throughout the day rather than waiting until you’re actually thirsty.
Why do you get headaches and find it harder to concentrate when you’re not drinking enough water?
Your brain consists largely of water, so it’s sensitive to your fluid balance. If you’re dehydrated, you’re more likely to feel tired, a bit drowsy or less focused, and some people get headaches as a result.
A well-known everyday example is the headache after a night of drinking: alcohol makes you urinate more, causing you to wake up dehydrated. The same principle applies on a smaller scale if you don’t drink enough during the day. A glass of water at the right time often prevents your concentration and mood from taking a dip as the day goes on.
How can you tell from your urine whether you’re drinking enough?
Your urine is the easiest indicator of your fluid balance. Light yellow to almost colourless usually indicates that you’re drinking enough, whilst dark yellow is a sign that you need to drink more.
| Colour | What it usually means (guideline) |
|---|---|
| Virtually colourless to pale yellow | You’re probably drinking enough |
| Straw-yellow, bright yellow | Fine, a healthy balance |
| Dark yellow to amber | A sign that you could drink more |
| Persistent brownish or cloudy colour | Drink water and keep an eye on it; if it persists, consult your GP |
Bear in mind that the colour can also be affected by other factors. For example, B vitamins make your urine a brighter yellow, and certain foods or medicines can cause a different colour. The colour is therefore a useful guide, not an exact measurement.
How much water do you need each day?
For most healthy adults, the guideline is around 1.5 to 2 litres of fluid a day. In hot weather, when exercising, or if you’re ill with a fever, your fluid requirements are higher, as you lose more fluid.
You also get some of your fluid from your food, such as vegetables, fruit, soup and yoghurt. The rest comes from what you drink. There is no exact standard that applies to everyone, so use your thirst and the colour of your urine as a practical guide. A few useful habits:
- Spread your fluid intake throughout the day rather than drinking a few large amounts at once
- Keep a bottle or glass of water in plain sight and within easy reach
- Drink more when it’s hot, during exercise and when you’re ill
Do you lose more than just water when you sweat?
Yes. Sweat isn’t just water; it also contains minerals known as electrolytes, such as sodium, potassium and magnesium. During prolonged and intense sweating, you lose these minerals as well as fluid.
On a normal day, you can easily replenish these losses with water and a varied diet. If you exercise for long periods in the heat, or if you sweat a lot, you lose minerals as well as fluid. Natural Electrolytes are made from coconut water powder and sea salt and contain, amongst other things, magnesium, potassium and calcium. Magnesium contributes to electrolyte balance. If you’d like to know more about this particular mineral, read about exactly what magnesium does for your body.
Frequently asked questions about water and dehydration
Can you drink too much water?
For most people, drinking too much water is rarely a problem: your kidneys simply excrete the excess. Only when consuming extremely large quantities in a short space of time – for example, during strenuous endurance sport without replenishing minerals – can your salt balance become disrupted. Listen to your thirst and spread your fluid intake throughout the day, and you’ll be fine.
Do coffee, tea and food count towards your fluid intake?
Yes. Coffee and tea count towards your fluid intake; caffeine has a mild diuretic effect, but on balance you’re still taking in fluid. Water-rich foods such as vegetables, fruit and soup also contribute to your total fluid intake.
What’s the quickest way to tell if I’m drinking enough?
Check the colour of your urine and pay attention to your thirst. Light yellow urine and the absence of persistent thirst usually indicate that your fluid balance is fine. Dark urine is the clearest sign that you need to have an extra glass.
Do you need a sports drink or electrolytes?
For everyday activity and short workouts, water is sufficient. During long, intense exercise or when sweating heavily in the heat, you lose minerals as well as fluids, and replenishing these can be useful. For most days, water remains the simplest and best starting point. You can read more about exactly what electrolytes are and when you need them in ‘What are electrolytes?’.
In short
You’ll notice you’re not drinking enough water if you feel thirsty, have a dry mouth, darker urine, a headache or find it harder to concentrate. Around 1.5 to 2 litres of fluid a day is a useful guideline, with more needed in hot weather and during exercise. Use the colour of your urine and your thirst as a guide, and bear in mind that when you sweat a lot, you lose minerals as well as fluid. Want to know more? Read ‘Drinking enough water: 5 reasons why’ or check out other articles on our knowledge blog.
