What is dehydration

Our bodies are made up of 70% water, which 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. As long as we each drink enough fluid every day our bodies stay 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 severity of dehydration can impact on the types of symptoms it causes, ranging from mild thirst to coma or death.

We get around two-thirds of the fluid we need 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 normal bodily functions such as breathing, urination and passing stools, 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.

The symptoms of dehydration

For most people, the first symptom of dehydration is feeling thirsty but other symptoms often develop before this, such as fatigue or tiredness, headache, and a dry mouth. After thirst comes dizziness, weakness and passing less urine which is often more concentrated and darker yellow than usual. As dehydration worsens, other symptoms may occur including a raised pulse rate, sunken eyes, an absence of sweating and extreme thirst. Blood pressure may fall and ultimately delirium (confusion) 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.

The signs in children may be less obvious and include fewer wet nappies, or not passing urine as much as normal, being more irritable or less active, not crying any tears when upset, having a sunken fontanelle (the soft spot on top of a baby’s head), dry or wrinkled skin and a rapid pulse and breathing rate.

Who is prone to dehydration?

Anyone can suffer from dehydration but there are risk factors that put certain groups of people at risk;

  • Sportsmen and sportswomen, and those who live or work in hot climates are more at risk of dehydrating if they do not drink enough fluids.
  • The elderly are less able to store water in their bodies, and their sense of thirst is less obvious than younger people, making dehydration more likely. This may be made worse when they are ill or disabled.
  • Viral illnesses increase the risk of dehydration due to a raised temperature, sweating, and the feeling of not wanting to eat or drink.
  • Chronic illnesses such as kidney disease can also increase the risk.
  • Young children and babies are more prone to suffering the effects of fluid loss due to their low body weight.

How is dehydration prevented?

Preventing dehydration is straightforward and is based on drinking enough fluid.  Most health authorities recommend drinking six to eight glasses of water each day (around 2 litres). If you live in a hot climate, or are exercising or taking part in strenuous activity then you should drink more – a good rule of thumb is an extra litre of fluid for every hour of exercise taken. Always aim to be passing urine a pale straw colour since the darker the colour of your urine the more dehydrated you are.

Treating mild dehydration

Mild dehydration is simply treated, by rehydrating and drinking more water and other fluids such as water, diluted squash, diluted fruit juice or semi-skimmed milk. A sweet drink can help to replace lost sugar. If necessary rehydration treatments are available from pharmacists.

Infants and children who are dehydrated shouldn't be given water as the main replacement fluid because it can further dilute the minerals in their body and make the problem worse. Instead, they should be given diluted squash, diluted fruit juice or a special rehydration solution. If you or your child is finding it difficult to hold down fluids because of vomiting or diarrhoea, take smaller amounts more frequently. If necessary, you could use a spoon or a syringe to give your child small amounts of fluids.

Treating severe dehydration

Severe dehydration often requires hospital admission for intravenous fluid replacement treatment. If you suspect that someone is severely dehydrated, you should seek medical attention immediately. In particular, babies, infants and elderly people will need urgent treatment if they become dehydrated.