Dehydration: How to Spot It in Adults and Children

Dehydration shows up in three things you can check without equipment: scanty dark urine, a dry mouth and tongue, and a change in alertness. Thirst is a poor guide — it is often absent in older people and unusable in infants. In an adult, no urine for more than 8 hours, dizziness on standing, or unusual drowsiness means being seen. In an infant, a dry nappy for 6 hours, sunken eyes or a sunken fontanelle are immediate warning signs.

Why thirst is not enough

Thirst appears late, and it blunts with age: an older person can be genuinely dehydrated without feeling it. An infant cannot express it. An adult who is vomiting often finds that drinking triggers nausea, so they give up before thirst even registers. That is why objective signs matter.

The three things to check

1. Urine

The most reliable everyday indicator. Pale, frequent urine means fluid balance is fine. Dark, strong-smelling urine, or gaps of more than 6 to 8 hours, means losses are outstripping intake. In infants, count wet nappies.

2. Mouth and skin

Dry tongue, cracked lips, no saliva. The skin pinch — gently pinching the skin on the back of the hand or the abdomen — takes more than a second to flatten when dehydration is marked. In older people this sign is less reliable, since skin naturally loses elasticity; the appearance of the tongue is more useful.

3. Alertness and behaviour

Unusual tiredness, irritability, difficulty concentrating, dizziness on standing. In children: a child who has stopped playing, cries without tears, or is unusually quiet is more concerning than one who is screaming.

What to drink, and how

• Small amounts, often. A few sips every 5 to 10 minutes stay down better than a full glass, especially with vomiting.
• Oral rehydration salts for diarrhoea or vomiting, particularly in children and older adults. This is the reference treatment: water, salt and sugar in precise proportions. Use the full volume of water printed on the sachet — a more concentrated solution makes diarrhoea worse.
• Failing that: water, salted broth, rice water. Very sugary soft drinks and neat fruit juice can worsen diarrhoea; dilute them.
• Avoid alcohol and strong caffeine during the episode.

High-risk situations in Tangier

Three contexts come up repeatedly on home visits in the city: gastroenteritis or food poisoning, where losses are fast; summer heat, especially in older people living alone and in children on the beach; and prolonged fasting, particularly when it coincides with an acute illness or a diuretic.

When should you be seen?

Same-day consultation

• Adults: no urine for 8 hours or more, dizziness on standing, unable to keep fluids down for over 6 hours.
• Children: fewer wet nappies than usual, refusing to drink, diarrhoea lasting more than 24 hours in an infant.
• Older adults: new confusion, a fall, sudden fatigue — dehydration often presents this way rather than as thirst.

Call the emergency services (15) immediately

• Deep drowsiness, difficulty rousing the person, marked confusion.
• Very fast pulse with cold, mottled hands and feet.
• A floppy, whimpering infant with a clearly sunken fontanelle.
• Loss of consciousness.

What an examination at home settles

A doctor checks blood pressure lying and standing, heart rate, mucous membranes and capillary refill, which gives a sense of severity. Moderate dehydration in an adult can be corrected on site with a drip, plus an anti-sickness injection if vomiting blocks oral intake. Severe dehydration, an unwell infant, or any doubt about kidney function needs hospital instead: that requires blood tests and monitoring that cannot travel.