Dehydration and hyponatremia: what to know

Dehydration is a shortage of body fluid. Hyponatremia means blood sodium is too low. Vomiting, diarrhoea, heavy sweating, some medicines, kidney problems, and excessive plain water can contribute in different ways. Nausea, headache, weakness, dizziness, and confusion may overlap.

Thirst and urine colour cannot diagnose low sodium. Examination and blood tests may be needed. The right response may involve replacing fluid, adjusting intake, or treating another illness, so large amounts of water or salt should not be used as guesswork.

Stop strenuous activity, rest, and seek clinical advice about the appropriate drink. Do not rapidly consume large volumes of plain water or take salt tablets unless prescribed. Bring a list of medicines, especially water tablets, and mention vomiting, diarrhoea, sweating, or heat exposure.

Heart, kidney, liver, or hormone conditions require individual guidance. Gastroenteritis may need treatment alongside any electrolyte disturbance.

Seek emergency help for confusion, seizure, severe drowsiness, collapse, difficulty waking, or repeated vomiting. Prompt assessment is needed when someone cannot drink, passes very little urine, or becomes increasingly weak or unsteady.

Ask whether sodium and kidney function should be checked, which fluids are appropriate, and whether medicine or recent illness changed fluid balance.