Hypertonic dehydration: what should you know?

Water loss from fever, sweating, rapid breathing, diarrhoea, vomiting or limited access to drinks can concentrate sodium in the bloodstream. The brain and other cells respond to this shift, so thirst, dry mouth, fatigue, irritability, headache or confusion may occur. Dark urine and constipation can accompany dehydration, but symptoms alone cannot show the body’s sodium level. Older adults, babies and people with swallowing, kidney or communication difficulties can become unwell quickly.

If the person is alert and able to swallow, offer frequent small sips of an appropriate fluid. Oral rehydration solution may be useful when fluid loss follows diarrhoea or vomiting; prepare it exactly as directed. Avoid trying to correct suspected high sodium with large amounts of plain water without medical advice, particularly when confusion, kidney disease or heart failure is present. A healthcare professional may need to check blood tests, urine, kidney function and the cause of fluid loss.

Get urgent medical help for confusion, unusual drowsiness, seizure, fainting, severe weakness, inability to drink, repeated vomiting or very little urine. Emergency assessment is also needed after significant heat exposure or when dehydration affects a baby, older adult or person with a serious medical condition. Do not give drinks to someone who is not fully awake or cannot swallow safely.

What caused the fluid loss, and does the person need sodium or kidney-function testing? Which rehydration fluid is suitable with existing conditions? How should drinks or medicines be adjusted while recovery is monitored?