What to do when you are dehydrated

Dehydration occurs when the body loses more fluid than it replaces. Thirst, dry mouth, tiredness, headache, dizziness, constipation, and dark urine can occur. Vomiting or diarrhoea from gastroenteritis, sweating during heat exhaustion, fever, and difficulty drinking are common settings. Older adults, young children, and people with some long-term conditions can become unwell more quickly.

Take frequent small sips of water or another suitable drink. After vomiting or diarrhoea, an oral rehydration solution can replace fluid and salts; follow the product instructions and ask a pharmacist if you have kidney or heart problems. Rest in a cool place when heat is involved. Continue appropriate food as you recover, and monitor how often you pass urine and whether its colour is becoming lighter. Avoid relying on alcohol.

Seek urgent medical help for confusion, fainting, severe weakness, very little or no urine, inability to keep fluids down, blood in vomit or stool, or signs of heat illness. Get prompt advice for a child, older person, or person with a significant medical condition who is becoming drowsy or unable to drink.

How much fluid is suitable for me? Should I use oral rehydration solution? Could my symptoms point to gastroenteritis, heat exhaustion, or another problem such as a urinary infection?