Clinical signs of dehydration

Fluid is lost through sweating, vomiting, diarrhoea, fever, or simply not drinking enough. As loss continues, the mouth and skin may feel dry, urine becomes more concentrated, and standing may make a person light-headed. Severe dehydration can affect alertness, circulation, and kidney function. Dark urine can be a clue, but urine colour also changes with some medicines and foods; it does not establish the cause by itself. Dehydration may occur with gastroenteritis or heat exhaustion, while urinary symptoms can point to another problem.

Take frequent small sips of water or an oral rehydration drink, particularly after vomiting or diarrhoea. Rest in a cool place and replace fluids steadily rather than drinking a large amount quickly. Continue suitable foods when able. Babies, older adults, and people with ongoing illness may worsen quickly, so arrange medical advice early. A clinician can assess fluid loss, medicines, and conditions such as kidney stones or a urinary tract infection.

Get urgent medical help for confusion, fainting, unusual sleepiness, inability to keep fluids down, very little or no urine, severe weakness, or fast breathing. Seek same-day advice when dehydration follows persistent vomiting or diarrhoea, occurs during heat exposure, or affects a child or frail adult. Cloudy urine, painful urination, or constipation may need assessment because dehydration is not the only possible explanation.

Explain how much you have been drinking, how often you urinate, and whether vomiting, diarrhoea, fever, sweating, or new medicines are involved. Ask which rehydration drink is suitable, how to monitor symptoms, and when blood or urine tests might be needed.