Neurological symptoms of dehydration

The brain and nerves depend on a steady supply of water, salts and blood flow. Losing fluid through vomiting, diarrhoea, sweating, fever or not drinking enough can cause thirst, dry mouth, headache and light-headedness. More serious dehydration may lead to unusual sleepiness, irritability, disorientation, muscle cramps or passing out. Neurological changes are not specific to dehydration, so a new or severe symptom may have another cause. Gastroenteritis and heat exhaustion are common situations in which fluid loss can build quickly.

Move to a cool place and rest. Take frequent small sips of water; an oral rehydration solution can help replace fluid and salts after heavy sweating, vomiting or diarrhoea. Avoid alcohol and strenuous activity while you feel unwell. If you are vomiting, begin with small sips and increase gradually. Keep track of whether you are passing urine and whether it is becoming lighter. Do not force fluids if you are confused, repeatedly vomiting or unable to swallow; seek urgent medical help.

Seek emergency help for confusion, collapse, a seizure, severe weakness, trouble speaking, one-sided weakness, a severe headache, or inability to keep fluids down. Get prompt medical advice if dizziness persists after drinking, urine becomes very dark or scant, or dehydration follows prolonged diarrhoea, vomiting or heat exposure. Children, older adults and people with kidney or heart conditions can worsen quickly and should be assessed early.

Ask what may be causing the fluid loss, whether you need an examination or blood tests, and which rehydration drink is suitable for you. Mention medicines, kidney problems, diabetes, pregnancy, vomiting or diarrhoea, and the time your neurological symptoms began.