Dehydration

When the body loses more fluid than it takes in. It can be mild or life-threatening, especially in children and older people.

FluidsLast updated: 21 October 2026

Quick Summary

Primary Symptoms

Thirst, dark yellow urine, passing less urine, dry mouth, tiredness, dizziness and headache.

Common Treatments

Drinking fluids and oral rehydration solution; intravenous fluids for severe dehydration.

Risk Factors

Diarrhoea and vomiting, hot weather, fever, heavy sweating, diabetes and not drinking enough.

OverviewSymptomsCausesTreatmentFAQ

Overview

The body needs water to work properly. Dehydration happens with illness, heat or not drinking enough.

Babies, young children and older adults can become dehydrated quickly. Severe dehydration is a medical emergency.

Symptoms

Dark urine

And passing urine less often.

Dizziness

Especially on standing.

Tiredness

And headache.

Severe signs

Confusion, no urine, sunken eyes, fast heartbeat: get urgent help.

Causes & Risk Factors

Biological Causes

Losing fluids through diarrhoea, vomiting, sweating or urine without replacing them.

Key Risk Factors

  • Illness Diarrhoea, vomiting and fever.
  • Heat Hot weather and exercise.
  • Age Infants and older adults.

Management & Treatment

01. Fluids

Sip water regularly.

02. ORS

Oral rehydration solution replaces salts and water lost in diarrhoea.

03. Hospital care

Intravenous fluids for severe dehydration.

Frequently Asked Questions

Are sports or soft drinks good for rehydration?
ORS is better for diarrhoea; sugary drinks can make diarrhoea worse.
How much should I drink?
Enough to keep urine pale yellow.

Sources and further reading

Last updated 21 October 2026. For more detail, see these trusted health organisations.