What should you know about intracellular dehydration?

Water moves between body compartments to keep the concentration of salts and other dissolved substances balanced. When the body loses more water than it replaces, water can move out of cells, including brain and muscle cells. Thirst, dry mouth, headache, tiredness, dizziness and reduced urination may occur. Urine may become dark, although colour is not a diagnosis; [Dark Urine](/symptoms/dark-urine/) also has other causes. Vomiting or diarrhoea from [Gastroenteritis](/conditions/gastroenteritis/) and sweating during [Heat Exhaustion](/conditions/heat-exhaustion/) can contribute.

If you are alert and able to drink, take frequent small sips of water. After vomiting or diarrhoea, an oral rehydration solution may replace both fluid and salts; follow the packet directions. Rest in a cool place after heat exposure, and avoid alcohol while recovering. Older adults, babies, people with kidney or heart problems, and anyone taking medicines that affect fluid balance may need individual advice. Persistent thirst, constipation or cloudy urine should not be self-treated indefinitely; [Dehydration](/conditions/dehydration/) can be assessed by a clinician.

Seek urgent care for confusion, unusual drowsiness, fainting, inability to keep fluids down, severe weakness, no urination, rapid breathing, or worsening symptoms after heat exposure. Emergency assessment is also needed with severe flank pain, fever or painful urination, because [Kidney Stones](/conditions/kidney-stones/) or a [Urinary Tract Infection](/conditions/urinary-tract-infection/) may need treatment.

What may be causing my fluid loss? Do I need an oral rehydration plan or blood tests? Could a medicine or kidney problem be affecting my balance? How much should I drink while I recover?