The causes of dehydration

What are the most common factors and causes of dehydration?

Dehydration occurs when the amount of water in the body is too low. Causes of dehydration include not drinking enough fluids, or losing a lot of fluids through sweating, particularly during hot weather, exercise or a fever, or a combination of these factors. Diarrhoea or vomiting can also cause dehydration. Diarrhoea causes an increased loss of water and electrolytes, including sodium, chloride and potassium. If these losses are not sufficiently replenished, a deficiency of water and electrolytes develops, causing dehydration.

What are the most common symptoms of dehydration?

There are various degrees of dehydration, ranging from mild to severe. Common symptoms of mild or moderate dehydration may include a dry mouth, tiredness, thirst, headache, dizziness or light headedness. It may also cause dry skin, a lack of tears when crying and constipation. Decreased urine output is another reliable indication of dehydration. In infants, this means no wet nappies for 3 hours and for older children and teenagers, no urination for eight hours or more. 

How can I prevent and/or treat dehydration?

Fortunately, dehydration is largely preventable in most cases by drinking plenty of fluids and eating foods that contain a lot of water, such as fruits and vegetables. Being guided by thirst is usually sufficient for most healthy people to remain properly hydrated but you can also view our guide on how much fluid do I need to stay hydrated. However, some patient groups or certain circumstances require special attention. These include:

  • In children – Fever, diarrhoea, vomiting or excessive sweating on a hot day or during exercise are all factors that may place children at risk of developing dehydration. The best way to prevent dehydration is to ensure that kids get plenty of fluids when they’re sick or physically active. Preventing dehydration can also depend on the circumstances. For example, a child with a sore throat may become dehydrated due to the inability to drink or eat easily. In this case, cold drinks or ice blocks can help with burning pain while also supplying fluids. Sports drinks are also not ideal, as they contain a lot of sugar and can worsen diarrhoea.
  • While travelling – Air conditioned environments and pressurised cabins in planes increase the loss of fluids from the skin and lungs. The risk of dehydration is therefore increased during travel, especially when transit times are long. It is recommended that you take your own drinks when travelling, especially when the journey is by rail or car. Although fluids are regularly offered during flights, the serving sizes are often too small to ensure adequate hydration. Water, sports drinks, juice and cold drinks are all suitable choices. Try to drink fluids regularly, for example, one cup an hour and avoid alcohol.
  • During pregnancy – Adequate hydration is particularly important during pregnancy and after birth to meet the physiological changes that occur during these times. Water is essential to form amniotic fluid which surrounds the baby, to support the increase in blood plasma volume and to produce breast milk. In the early stages of pregnancy, morning sickness may cause vomiting which can lead to fluid loss. Severe vomiting during pregnancy, known as hyperemesis gravidarium, can cause dehydration symptoms. Women experiencing severe vomiting during pregnancy should consult their healthcare professional. The recommended daily water intake (from food and drinks) for women is 2000ml. Pregnant women should take in 300ml over and above this amount in order to prevent dehydration.
  • During illness – Illnesses causing vomiting, diarrhoea and fever may cause dehydration. Electrolyte solutions may be able to assist the treatment of dehydration. It is better to drink small amounts of fluid (using a teaspoon or syringe for infants and small children) instead of large amounts at one time, as this can trigger more vomiting. Begin fluid replacement as soon as vomiting and diarrhoea start and don’t wait for dehydration symptoms to appear.
  • During strenuous exercise or sport – In order to prevent dehydration, always start sport well hydrated. Drinking fluids during exercise is necessary to prevent a drop in performance due to dehydration. The adverse effects of dehydration on performance may include an increase in the perception of how hard the exertion is, increased risk of heat stress and a loss of coordination. Thirst is not a reliable indicator of hydration level during exercise, as fluid losses may be significant by the time thirst develops. Also, your thirst will be satisfied well before those losses have been replenished.
  • At work – When performing physical work, fluid losses through sweat often exceed fluid intake. Dehydration can negatively affect worker productivity, safety and morale. Physical activity level, clothing/ equipment and weather are important in determining a worker’s fluid needs. Workplaces that are in warm environments and/or involve high levels of physical activity will require greater fluid replacement in order to prevent dehydration.
  • In extreme heat – Extreme heat may cause heat emergencies such as heat cramps, heat exhaustion and heatstroke. If the problem is not addressed, heat cramps (caused by a loss of salt during heavy sweating), may progress to heat exhaustion, (caused by dehydration) and finally heatstroke, which is the most severe. Dehydration can be prevented in extreme heat by wearing light, loose fitting clothing, resting frequently and seeking shade when possible and by drinking plenty of fluids.
  • Excessive alcohol intake – Alcohol increases the risk of dehydration because it has a diuretic effect on the body. This means that it causes a greater loss of fluids and electrolytes from the body than is gained when drinking it. Excessive alcohol consumption may also lead to vomiting, further increasing fluid losses. The best way to prevent dehydration from alcohol intake is to drink only small to moderate amounts and increase your intake of nonalcoholic fluids as well. For example, you can alternate between an alcoholic drink and a glass of water during dinner or a night out.

What is the best way to treat dehydration once it’s been diagnosed?

Electrolyte solutions may be able to assist the treatment of dehydration. They are widely available in pharmacies and should be administered as soon as possible to anyone with diagnosed dehydration.

Always read the label. Follow the directions for use. If symptoms persist, talk to your health professional. Vitamin supplements should not replace a balanced diet

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