6 common dehydration symptoms

·6-min read
Photo credit: MarioGuti - Getty Images
Photo credit: MarioGuti - Getty Images

Drinking plenty of water every single day is essential, particularly in warm weather. Dehydration can develop if your body loses more fluids than you take in and symptoms include headaches, lethargy, constipation and in severe cases may require urgent medical attention.

But what exactly is dehydration, and how do you know when you’re dehydrated? Dr Roger Henderson looks at dehydration symptoms, causes, treatment and how to ensure you're hitting your daily water quota:

What is dehydration?

The human body is mainly water – 70 per cent is made up of water and it is vital for all aspects of the normal functioning of the body including healthy functioning of joints and skin, digestion, waste product removal and muscle and nerve function. Provided enough fluid is drunk each day the body remains hydrated and, in the absence of illness, the body functions as it should. However, if more fluid is lost from the body than is absorbed then dehydration occurs and this may be mild, moderate or severe depending on how much fluid is lost. The symptoms it causes also depends on the severity of the dehydration, ranging from mild thirst to coma or death.

We get around two-thirds of the fluid we require from drinks, with the rest coming from fluid in foods and as a result of normal chemical reactions in the body. Most people lose between two and three litres every day through our normal bodily functions such as breathing, urination, defecation and sweating. Factors that can increase fluid loss include sweating in hot weather or with a high temperature, diarrhoea and vomiting, diabetes, exercise, excessive alcohol intake and simply not taking enough fluid during the day.

Photo credit: Valeriia Sviridova / EyeEm - Getty Images
Photo credit: Valeriia Sviridova / EyeEm - Getty Images

Dehydration causes

What causes dehydration? It’s completely normal to lose water through your body each day, through sweat, breath, urine, faeces, saliva and tears. However, if you don’t replace this water by drinking or eating foods with a high water content, you will likely become dehydrated. Other risk factors of dehydration include:

  • Vomiting or have diarrhoea

  • High fever

  • Sore throat (meaning you may not want to drink or eat much)

  • Vigorous exercise

  • Heatstroke

  • Drinking lots of alcohol

  • Diuretic medication (which makes you need to wee more frequently)

  • Diabetes

Dehydration signs and symptoms

If you're thirsty, chances are you know to reach for a glass of water. But for small children and the elderly, it's not always apparent. Fortunately there are a number of signs to look out for which indicate you may need to hydrate:

1. Thirst

For most people, the first symptom of dehydration is feeling thirsty.

2. Headaches and fatigue

Others often develop before this such as fatigue, headache, and a dry mouth.

3. Dizziness

Following thirst comes dizziness and weakness.

4. Darker urine

Passing less urine which is also often more concentrated and darker yellow than usual.

5. Raised pulse rate

As dehydration worsens, other symptoms may occur including a raised pulse rate, sunken eyes, an absence of sweating and extreme thirst.

6. Delirium

Blood pressure may fall and ultimately delirium and loss of consciousness occurs. People who have low-level chronic dehydration are more prone to conditions such as kidney stones, chronic fatigue and kidney stones.

⚠️ While mild dehydration can be rectified by quenching your thirst, at its most severe, dehydration can be life threatening.

Dehydration in babies and children

Young babies, toddlers and the elderly are most prone to getting dehydrated as they may not recognise when they are thirsty, so it's important to look out for the key signs.

If your baby or young child is dehydrated, you may notice these additional symptoms, as well as the symptoms listed above:

  • Playing less and seeming subdued or irritable.

  • No wet nappies for three hours or more.

  • A sunken fontanel (the soft spot on top of your baby’s head).

  • A lack of actual tears when they cry.

Dehydration treatment in babies and children

As soon as you suspect your baby or young child may be dehydrated, offer them water to drink. Babies under one year should be given the chance to breastfeed as often as they wish, or offered formula milk. Young children may refuse plain water, in which case you could try the following:

✔️ Offer your child milk or very diluted squash.

✔️ Spoon-feed your child small amounts of water – little and often is best.

✔️ Offer your child slices of melon, strawberries or grapes (cut in half lengthways).

✔️ Offer your child an ice lolly.

If your child has a vomiting or diarrhoea bug, it’s important that they keep drinking fluids. Encourage them to take regular small sips of water. You should also offer them a rehydration solution – speak to your pharmacist about which is the best choice for your child.

⚠️ If your child refuses all offers of drink or food, and you are in any way concerned about their level of dehydration, call 111 for advice. You may be advised to visit your local A&E department, where (in serious cases) your child may be rehydrated using an IV drip.

Dehydration in the elderly

Dehydration in older people can cause serious risks if it gets severe, including kidney stones, fainting and low blood pressure.

Mobility issues can increase an elderly person’s chance of suffering from dehydration: if they are unable to easily stand and move around independently, they will be far less likely to regularly get up to fetch themselves a glass of water.

Dehydration treatment in the elderly

The best way for all of us to rehydrate and avoid becoming dehydrated in the first place is to drink plenty of water. Coffee, tea, fruit juice, sweetened beverages, fruits and vegetables all contain water, so if someone you know does not like drinking plain water, try to encourage them to up their intake of these other drinks or foods containing water.

Jellies, ice lollies and melons are all good alternatives, especially when encouraging an elderly person to increase their fluid intake. Encourage them to keep a water jug or bottle close by, so they’re more inclined to drink more often but always make sure the water container isn’t too big though, as they may struggle to lift and pour it. Instead, it’s better to use a smaller jug that you can refill regularly for them. Try using an app or set an alarm to remind them to drink at regular intervals, especially at mealtimes.

Dehydration treatment during a sickness bug

If you have been unwell with a sickness or diarrhoea bug, you will likely have lost water, as well as other vital nutrients.

It can sometimes be hard to keep drinking and to keep fluids down, but try to sip small amounts of fluid on a regular basis, to keep hydrated and replenish what you have lost. It is helpful to use a rehydration solution (added to water), as these contain sugars and salts, which your body will have lost. Speak to your pharmacist to help you decide which rehydration solution may be best for you.

Last updated: 07-07-2021

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