Health Library · General Health

Dehydration symptoms

Overview

Dehydration develops when fluid loss exceeds intake — GI illness, heat, exercise, or inadequate drinking. Older adults are particularly vulnerable.

Symptoms to watch for

  • Thirst
  • Dry mouth
  • Dark urine or reduced urination
  • Fatigue
  • Dizziness with standing
  • Headache
  • Muscle cramps

Treatment

Oral rehydration for mild-moderate. IV fluids for severe or when oral not tolerated.

When to book a visit

Book for persistent dehydration or if unable to keep fluids down.

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Frequently asked

How much water should I drink a day?

The 8-glass rule isn't evidence-based. Aim for pale-yellow urine — most adults do fine on 2–3 L total fluids/day, including from food. More in heat and exercise.