Signs of moderate dehydration

Dehydration happens when the body loses more fluid than it replaces. Vomiting, diarrhoea, sweating, heat exposure, fever or difficulty drinking can contribute. Urine may become darker and less frequent, while the mouth feels dry and the person may feel weak, light-headed or headachy. Cloudy urine or constipation can have other explanations, so they should not be used alone to judge fluid status.

Take frequent small sips of water or an oral rehydration drink, especially after vomiting or diarrhoea. Rest somewhere cool and pause strenuous activity. If nausea is present, small amounts taken often may be easier than a large drink. Continue suitable food when able. Monitor alertness, thirst, urine colour and how often urine is passed. Children, older adults and people with ongoing illness may need earlier medical advice.

Seek urgent help for confusion, unusual sleepiness, fainting, very little or no urine, inability to keep fluids down, rapid breathing, severe weakness or worsening dizziness. Get medical advice when fluid loss follows persistent diarrhoea, repeated vomiting, heat exposure or a fever, or when symptoms are not improving with sipping fluids. Severe pain in the side or blood in urine needs assessment because another problem may be present.

What may be causing the fluid loss? Is an oral rehydration drink suitable for me? Do my medicines or health conditions change how much I should drink? Which symptoms mean I should seek urgent care?