Dehydration treatment: what to know

Mild fluid loss is often managed with regular drinks and attention to the illness or activity that caused it. Water may be suitable after sweating, while oral rehydration solution is useful when vomiting or diarrhoea has also removed salts. A clinician may need to assess blood pressure, pulse, urine and blood tests when dehydration is more marked or the cause is unclear.

Treatment is also about stopping further loss. Gastroenteritis may need a different plan from heat exhaustion, and medicines or conditions affecting the kidneys or heart can change fluid advice.

Take small, frequent sips and increase gradually as nausea settles. Follow the instructions on any oral rehydration product; do not make it stronger than directed. Rest in a cool place after heat exposure and replace wet clothing if you are sweating heavily. Avoid alcohol, and seek advice before deliberately drinking large amounts if you have a fluid-restricted medical condition.

Get urgent help for confusion, collapse, seizure, severe weakness, inability to swallow or keep fluids down, or very little or no urine. Same-day assessment is sensible for ongoing diarrhoea or vomiting, worsening dizziness, a persistent fever, blood in vomit or stool, or dehydration in a baby, older adult or person with a serious long-term condition.

Ask which fluid is appropriate, how to manage the underlying cause, whether your medicines should change temporarily, and how you will know that hydration has returned to a safe level.