What should you know about dehydration symptoms fever?

A fever often occurs because of an infection or another inflammatory illness. The fever itself can increase fluid needs, and sweating, vomiting or diarrhoea may increase losses further. Dehydration symptoms can include thirst, sticky mouth, headache, weakness, dizziness and darker or less frequent urine.

Fever and dehydration can therefore appear together without one proving the cause of the other. Gastroenteritis may cause fever with vomiting or diarrhoea, while heat exhaustion can cause overheating and fluid loss. Confusion, fainting or severe drowsiness are warning signs regardless of the fever’s cause.

Rest, wear light clothing and take small, frequent sips of water. If vomiting or diarrhoea is causing loss, use an oral rehydration solution exactly as directed to replace salts as well as fluid. Continue suitable food as tolerated. Do not rely on thirst alone, and avoid alcohol while recovering.

Record the fever pattern, fluid intake and urine output. Fever medicine may be unsuitable with some illnesses or medicines, so follow label directions and ask a clinician or pharmacist when unsure. See [Dehydration](/conditions/dehydration/) for additional guidance.

Seek urgent help for confusion, fainting, severe drowsiness, breathing difficulty, inability to keep fluids down or very little urine. Obtain prompt medical advice when fever persists, weakness worsens, severe pain develops, a rash appears, or the person is a baby, older adult, pregnant or living with a long-term condition.

Ask what may be causing the fever, how much fluid is appropriate for your health, whether an oral rehydration solution is suitable and which symptoms should trigger reassessment. Mention recent travel, heat exposure, vomiting, diarrhoea and urine changes.