Signs of Dehydration in Adults: What to Look For and What to Do

Early Signs of Dehydration

According to NHS and HSE guidance, the most common early signs in adults are:

• Feeling thirsty.
• Dark yellow, strong-smelling urine.
• Peeing less often than usual; the HSE uses fewer than four times a day as a guide.
• Feeling dizzy or lightheaded.
• Feeling tired.
• A dry mouth, lips and tongue, or sunken eyes.

Urine colour is one of the easiest things to check. Pale straw-coloured urine usually means you are drinking enough; darker urine is a sign to drink more. Urine colour and bathroom visits are rough guides, not a diagnosis: some vitamins, foods and medicines change urine colour, and normal frequency varies from person to person, so look at the overall pattern alongside how you feel.

Symptoms That Need Urgent Help

Get urgent medical help, or call your local emergency number, if someone with signs of dehydration:

• Is confused or disorientated.
• Feels very dizzy, or dizziness does not go away when they stand.
• Has not peed all day.
• Is unusually drowsy or hard to wake.
• Has a fast heartbeat, fits or faints.
• Has had vomiting or diarrhoea for more than 24 hours and cannot keep fluids down.

Babies, young children and older adults can become dehydrated quickly and may not show thirst clearly. In babies, the NHS lists signs such as a sunken soft spot on the head, few or no tears when crying, and fewer wet nappies. If you are worried about a baby, child or older adult, contact a doctor or your local health advice line sooner rather than later.

Common Causes

Dehydration usually comes from losing extra fluid or not drinking enough to keep up.

• Hot weather and heat waves.
• Exercise, especially long sessions or training in the heat.
• Vomiting, diarrhoea or a high temperature.
• Drinking a lot of alcohol.
• Some medicines, such as diuretics, and conditions such as diabetes.
• Simply forgetting to drink during a busy day.

How to Rehydrate

For mild dehydration, drinking more fluids is usually enough. Sip water steadily rather than drinking a large amount at once, especially if you feel sick. If you have been vomiting or have diarrhoea, a pharmacist can recommend oral rehydration solution sachets, which replace salts and sugars as well as water.

If symptoms do not improve after drinking more, or you cannot keep fluids down, contact a doctor or pharmacist. If a doctor has told you to limit fluids, for example because of a heart or kidney condition, follow their advice rather than general drinking tips.

How to Prevent It

Most everyday dehydration is about routine. Drink regularly through the day rather than waiting until you are very thirsty, and drink more in hot weather, when exercising and when you are unwell. Keep a bottle within reach at work, and check the colour of your urine now and then.

If you often forget, reminders help. Water Reminder - DropWise sends reminders during the hours you choose, can adjust your suggested goal to local weather, and logs water and other drinks in one daily total. It supports everyday habits and is not a medical device.