Can dehydration cause nausea?

Nausea may come with thirst, dry mouth, headache, tiredness, dizziness, darker urine, or passing urine less often. Vomiting and diarrhoea can cause the fluid loss that starts or worsens this pattern. Heat exposure, illness, medicines, pregnancy, and other stomach or metabolic problems can also cause nausea. The symptom does not identify dehydration by itself. Pay attention to whether you can keep fluids down and whether your urine output is falling.

Rest and take tiny, frequent sips rather than drinking a large amount at once. Water may be suitable for mild losses; after repeated vomiting or diarrhoea, an oral rehydration solution can replace water and salts when used according to its instructions. Plain foods may be easier once nausea settles. Avoid alcohol and strenuous activity. If heat triggered symptoms, move to a cool place. [Gastroenteritis](/conditions/gastroenteritis/) and [Heat Exhaustion](/conditions/heat-exhaustion/) can both involve fluid loss.

Get urgent help for confusion, fainting, severe abdominal pain, blood or green material in vomit, severe weakness, or inability to keep even small sips down. Seek prompt advice if you are passing very little urine, symptoms are worsening, or nausea continues without a clear illness. Severe side pain or urinary changes may need assessment for [Kidney Stones](/conditions/kidney-stones/), while fever and painful urination can occur with a [Urinary Tract Infection](/conditions/urinary-tract-infection/).

Ask which rehydration fluid is appropriate, whether you need an anti-nausea treatment, and what signs mean you should return for help. Explain when nausea began, how often you have vomited or had diarrhoea, what you can drink, your urine output, and any medicines or recent heat exposure.