What should you know about dehydration leads to?

Fluid helps maintain blood volume, temperature control, digestion, and urine production. As fluid falls, you may develop thirst, dry mouth, headache, tiredness, dizziness, darker urine, or fewer trips to the toilet. Constipation may worsen because the bowel has less water available. More concentrated urine can encourage crystal formation in people prone to kidney stones. Dehydration caused by vomiting, diarrhoea, fever, heat exposure, or medicines may progress faster. Older adults, children, and people with some long-term conditions may not recognise thirst early.

Replace fluids steadily and address the reason for the loss. Take small, frequent sips if nausea makes drinking difficult. An oral rehydration solution can replace water and salts after significant vomiting or diarrhoea. Rest somewhere cool after heat exposure and avoid alcohol while recovering. Keep track of urine output and seek advice before changing fluids if you have heart, kidney, or liver disease or a prescribed fluid limit. Do not rely only on thirst.

Seek urgent care for confusion, fainting, severe drowsiness, inability to drink, repeated vomiting, or almost no urine. Same-day assessment is appropriate when dizziness does not settle, symptoms are worsening, or there is severe side pain, fever, blood in urine, or ongoing diarrhoea. These features may point to a complication or another illness, including kidney stones or a urinary infection.

Ask which fluid replacement is suitable for your symptoms and medicines, how to recognise worsening dehydration, and whether your medical history changes your daily fluid plan.