What can dehydration lead to?

When the body loses more fluid than it replaces, the mouth may feel dry and urine may become darker or less frequent. People may develop tiredness, dizziness on standing, headache, constipation, muscle cramps, or a fast heartbeat. More serious dehydration can reduce alertness and place stress on the kidneys. Causes include illness with vomiting or diarrhoea, fever, heavy sweating, heat exposure, and difficulty drinking. The consequence depends on the person’s health and how quickly fluid is lost.

Move away from heat and rest. Drink small, regular amounts rather than forcing a large volume at once. After vomiting or diarrhoea, an oral rehydration solution may replace water and salts; ask a pharmacist how to use one. Continue suitable foods if tolerated. People with kidney, heart, or liver conditions, or a prescribed fluid limit, should seek individual advice before increasing intake.

Seek urgent help for confusion, fainting, severe weakness, inability to keep fluids down, very little urine, or worsening dizziness. Heat-related illness with hot skin, altered behaviour, or collapse is an emergency. Arrange assessment when symptoms persist despite drinking, when fluid loss is ongoing, or when urine changes come with pain, fever, or blood. Kidney stones and urinary infection can also cause urinary symptoms and need their own evaluation.

What caused the fluid loss? Is an oral rehydration solution suitable? How much should I drink with my medicines or chronic condition? Do my urine or bowel changes need testing? Which symptoms mean I should return urgently?