Dehydration

What is dehydration?

Dehydration occurs when your body loses more fluid than it takes in, so it does not have enough water to carry out its normal functions. Water is essential for nearly everything the body does — regulating temperature, carrying nutrients, removing waste, and keeping cells working — so when fluid levels drop too low, the body starts to struggle. Dehydration can range from mild, which is very common and easily fixed, to severe, which is a medical emergency.

We lose fluid all the time through normal processes like breathing, sweating and passing urine, and usually replace it by drinking and eating. Dehydration develops when this balance tips — either because we are losing more fluid than usual, for example through illness or heat, or because we are not taking in enough. The good news is that most dehydration is mild and quickly corrected by drinking more fluids. Recognising it early, especially in those most at risk, prevents it from becoming serious.

Signs and symptoms

The signs of dehydration range from mild and easily missed to more serious. Recognising the early signs allows you to correct it before it worsens. Common signs include:

• •Feeling thirsty
• •Dark yellow, strong-smelling urine
• •Passing urine less often than usual
• •Feeling dizzy or lightheaded
• •Feeling tired
• •A dry mouth, lips and eyes
• •In more serious cases: sunken eyes, rapid heartbeat, confusion, and very little or no urine

Common causes

Dehydration happens when fluid loss outpaces fluid intake, and several situations can cause this. Common causes include:

• •Illness with diarrhoea and vomiting, a very common cause
• •Fever, which increases fluid loss
• •Hot weather or a hot environment, causing sweating
• •Exercise, particularly intense or prolonged activity
• •Simply not drinking enough fluids
• •Drinking a lot of alcohol
• •Some conditions and medicines that increase fluid loss

How to rehydrate safely

For most mild dehydration, the treatment is simply to drink more fluids. Water is usually suitable, and it is best to drink steadily in regular amounts rather than large quantities all at once. For dehydration caused by illness like diarrhoea and vomiting, or from heavy sweating, oral rehydration sachets from a pharmacy are particularly helpful, as they replace not just water but also the salts (electrolytes) the body loses, in the right balance.

If you are dehydrated through illness and struggling to keep fluids down, taking small, frequent sips is easier to manage than large drinks. Addressing the underlying cause — treating the illness, cooling down, or resting from exercise — helps too. Most mild to moderate dehydration resolves quickly with these measures. However, severe dehydration, or dehydration in someone who cannot drink or keep fluids down, needs urgent medical treatment, sometimes with fluids given directly into a vein, so it is important to seek help when the signs point to something more serious.

Dehydration in children and older adults

Two groups are particularly vulnerable to dehydration and deserve special attention: young children and older adults. Babies and young children can become dehydrated quickly, especially during illness with diarrhoea and vomiting, because they have a smaller fluid reserve and lose fluid rapidly. Signs of dehydration in a child include fewer wet nappies, dryness of the mouth, drowsiness or irritability, sunken eyes or (in babies) a sunken soft spot on the head, and cold or blotchy hands and feet. These warrant seeking advice promptly.

Older adults are also at higher risk, partly because the sense of thirst can lessen with age, so they may not feel thirsty even when they need fluids, and partly because certain medicines and conditions increase fluid loss. In older adults, signs like confusion, dizziness, tiredness and passing little urine can indicate dehydration and should be taken seriously. Encouraging regular drinking through the day, even without thirst, helps prevent it.

For both groups, prevention and early action are key. Offering fluids regularly, watching for the warning signs, and seeking medical advice early if dehydration is suspected can prevent it from becoming serious. Because these groups can deteriorate more quickly, it is always better to seek advice sooner rather than waiting, particularly during illness or hot weather when the risk is highest.