Dehydration happens when the body loses more fluid than it takes in. It can develop during hot weather, exercise, fever, vomiting or diarrhoea, and some medicines or medical conditions can increase risk. Fluid needs vary with age, activity, climate and health status.
Common signs
Thirst, dry mouth, darker urine, urinating less often, tiredness and dizziness can be signs of dehydration. Symptoms may be harder to recognise in infants, older adults and people who are unwell. Severe dehydration can be dangerous.
How to reduce the risk
- Drink fluids regularly, particularly during hot weather and physical activity.
- Take breaks in shade or cooler areas during heat and avoid strenuous activity during the hottest part of the day when possible.
- If vomiting or diarrhoea occurs, ask a healthcare professional or pharmacist about oral rehydration solution and how to use it.
- Older adults, young children and people with chronic illness may need extra attention during hot weather or illness.
- If you have heart or kidney disease or have been told to limit fluids, follow your clinician’s individual instructions.
When to seek urgent help
Seek urgent medical care for confusion, fainting, inability to keep fluids down, very little urine, severe weakness or other signs of serious illness. Infants and young children can worsen quickly, so seek prompt advice when concerned.
Frequently asked questions
Is urine colour a perfect measure of hydration?
No. It can offer a rough clue, but medicines, foods and medical conditions can change urine colour.
Are sports drinks always necessary?
No. Water is sufficient for many everyday situations; the best option depends on the duration of activity, fluid losses and individual health needs.
Further reading: NHS dehydration guidance.
Medical disclaimer: This article is informational only and does not replace medical advice, diagnosis or treatment.
