Symptoms of Dehydration

Dehydration announces itself politely at first and dangerously later. Knowing the sequence lets you fix it at the polite stage.

Early signs (act now, easily fixed)

• Thirst - the first alarm, though a late one in the elderly
• Dark yellow urine and passing less of it - the most reliable home gauge (aim for pale straw colour)
• Dry mouth and lips
• Tiredness, a dull headache, feeling flat

Moderate signs (drink electrolytes now, watch closely)

• Very little urine, very dark
• Dizziness on standing up
• Dry, less elastic skin
• Fast heartbeat, irritability
• In babies: fewer wet nappies, a sunken soft spot (fontanelle), no tears when crying

Severe signs (hospital, IV fluids - do not wait)

• No urine for 8 hours or more
• Sunken eyes
• Confusion, unusual drowsiness or lethargy
• Very fast heartbeat or breathing
• Fainting, cold hands and feet
• In children: floppy, unresponsive, or too weak to drink

The special cases

• Babies can go from fine to serious within hours during diarrhoea - watch wet nappies and alertness, not just thirst
• Elderly people often skip the thirsty stage entirely and present as "suddenly confused" - any abrupt confusion in summer deserves fluids first and a doctor's call
• Heatstroke territory: hot dry skin, body temperature above 40 C, confusion - that is 112, with cooling started immediately

One-line summary

Thirst and dark urine are early dehydration - fix with fluids now; no urine for 8 hours, sunken eyes, confusion or fainting are severe dehydration - hospital and IV fluids, with babies and the elderly deserving the lowest threshold for help.