What should you know about extreme dehydration?

Fluid loss can follow vomiting, diarrhoea, fever, heavy sweating, heat exposure, or difficulty drinking. Early signs include thirst, dry mouth, headache, tiredness, darker urine, and passing urine less often. As dehydration worsens, dizziness on standing, weakness, fast heartbeat, confusion, fainting, and very little urine may develop. Heat exhaustion and gastroenteritis are possible settings, but symptoms can have other causes. Dark urine may reflect concentrated urine, while cloudy urine, burning, fever, or side pain can point towards a urinary or kidney problem rather than dehydration alone.

Move to a cool place and rest. If you are awake, able to swallow, and not repeatedly vomiting, take small frequent sips of water or an oral rehydration drink. Continue gradually rather than drinking a large volume quickly. For diarrhoea or vomiting, ask a pharmacist or clinician about a suitable rehydration solution. Avoid alcohol and strenuous activity while recovering. If you have heart, kidney, or liver disease, or have been told to restrict fluids, obtain personalised advice instead of forcing fluids. Do not give drinks to someone who is confused, faint, or unable to swallow safely.

Seek emergency help for confusion, fainting, severe weakness, inability to keep fluids down, very little or no urine, rapid breathing, chest pain, or a fast or irregular heartbeat. After heat exposure, urgent assessment is also needed for worsening headache, collapse, or altered behaviour. Prompt review is appropriate for dehydration with blood in vomit or stool, severe abdominal pain, fever, or flank pain. Children, older adults, and people with significant medical conditions can deteriorate quickly.

Ask what likely caused the fluid loss, whether you need an oral rehydration solution or supervised treatment, how to monitor urine and symptoms, and when normal activity is safe. Mention all medicines, especially water tablets, and any kidney or heart condition.