It’s easy to overlook, but making sure we drink enough water is often quite low on our priority list.

But are we putting ourselves at grave risk by doing so?

“Your immune system relies on water,” says Dr Marilyn Glenville, author of Natural Alternatives to Sugar. “It carries nutrients to the cells, carries waste and toxins away from the cells and out of the body, keeps body temperature stable, protects joints and keeps the lining of your mouth hydrated and moist, reducing susceptibility to colds.

“Drinking plenty of water will also flush out waste and dilute mucus, helping eliminate bacteria and viruses that can make you ill.”

And here are the surprising side effects of forgetting to drink water.

1. You are feeling tired

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Our bodily fluids are comprised of water so when you get dehydrated, your blood becomes thicker and your heart has to use more energy to keep oxygen and other nutrients moving through the circulatory system.

“The body’s way of conserving energy as it may not be functioning as efficiently in a hypo-hydrated state,” says Dr Emma Derbyshire of Natural Hydration Council.

The Natural Hydration Council says one in 10 cases of tiredness are attributed to dehydration.

2. You are having digestive problems

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“We all know that fibre is an essential nutrient in the digestive process, but without enough water, it can easily lead to constipation,” says Dr Adam Simon, chief medical officer at PushDoctor.co.uk.

“Simply put, water makes it easier for you to go the toilet, softening your poo so that it’s easier to pass.

“Some studies have also claimed that not drinking enough water makes it more likely that you’ll develop stomach ulcers.”

3. Your eyes are sore

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Your eyes will become dry, irritated and bloodshot if they don’t get enough water.

“That’s because they’re usually protected by a thin film of moisture which, like your tears, contains water and salt,” says Dr Simon.

“If the salt isn’t sufficiently diluted, your eyes will feel it. This lack of moisture will also make life particularly miserable for people who wear contact lenses.”

4. You have an increased risk of kidney stones

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“Dehydration can lead to the formation of kidney stones,” says Dr Simon.

“While most are small and can be passed out by the body, if kidney stones are large enough, they can block the urinary tract and cause stomach or groin pain.

“If you become severely dehydrated, there’s a chance you could develop acute renal failure.”

5. You have bad breath

“Keeping hydrated is essential for general wellbeing, but you may be surprised to know it is also essential to keep your breath in check too,” says Luke Thorley, of Welling Corner Dental Practice and brand ambassador for CB12.

“Regular glasses of water help to maintain saliva flow, which washes away the ‘bad bacteria’ that cause unpleasant breath.”

6. You have aching joints

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Joints need fluid to stay lubricated in order to function.

“It’s important for your joints to stay lubricated in order for them to work properly,” says Dr Simon.

“Getting plenty of fluids will help keep cartilage soft, which reduces your chances of developing arthritis or other joint problems.”

7. You have a headache

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“The loss of even 1-2% of body weight – equating to 500 ml to two litres – can bring on headache symptoms,” says Dr Carrie Ruxton, a member of the Tea Advisory Panel.

“Alongside this, you may feel dizzy or lethargic. Start replacing fluid straight away if a headache comes on by sipping water steadily.”

8. Your cholesterol levels are higher than normal

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Without water, your body will produce more cholesterol in order to ensure your cell membranes stay moist and can continue to process both nutrients and waste products.

“Of course, we know the dangers of high cholesterol, which can increase your chance of life-threatening problems such as heart attacks and strokes,” Dr Simon adds.

9. Your concentration levels are falling

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Finding it hard to focus at work? Your room may have something to do with it.

“Stress, long commutes, air conditioning and heating can all increase water loss even when you don’t feel particularly sweaty,” adds Dr Ruxton.

“The brain represents only 2% of the body’s weight, but gets 20% of blood circulation.

“That means that dehydration affects the brain far earlier than the body as the brain relies on a steady supply of oxygen and nutrients.”

10. You are finding simple exercises hard to do

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“Physical performance is affected when dehydration hits around 1-3% of body weight, so water should be your most important accessory in the gym,” says Dr Ruxton.

“When exercising for short periods or at low intensities, a bottle of tap water will do.

“Longer periods of exercise, around 40-60 minutes, tend to cause losses of salts as well as fluid so a sports drink would be a better option.”

What to do

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The Eatwell Guide says we should drink six to eight glasses of fluid a day.

The European Food Safety Authority recommends an intake of 2.5 litres of water for men and two litres of water for women per day, through food and drink consumption.

But bear in mind, that there is such a thing as drinking too much water.

As Natural Hydration Council explains: “Over-hydrating with any fluid is possible, and in extreme cases it can be dangerous, but, this is very rare.

“Hyponatremia results from abnormal water retention throughout the body. This reduces the blood sodium concentration, causing excess fluid to move from the blood into the tissue cells, including the brain.”