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By Gunal M
Dehydration happens when you lose more fluid than you take in. It is common, it is usually mild, and it is easy to miss. The good news is that your body gives you clear signals, and most of them are easy to read once you know what to look for.
Below you will find the common signs of dehydration in adults, the warning signs that need urgent care, who is at higher risk, and a simple routine to stay ahead of it. This is general information, not medical advice.
Quick check: look at your urine. Pale yellow means you are doing well. Dark yellow or strong-smelling urine, or peeing less than usual, means you need more fluid.
What are the signs of dehydration?
The NHS and MedlinePlus list these common symptoms in adults (NHS, MedlinePlus):
- Thirst and a dry mouth. Dry mouth, lips and tongue are among the first things you notice.
- Dark, strong-smelling urine. Concentrated urine is the clearest sign. Aim for a pale colour.
- Peeing less often than usual, and sweating less.
- Headache. A dull headache can be a sign you need fluid.
- Feeling tired. Fatigue is common even with mild dehydration.
- Dizziness or light-headedness, especially when you stand up.
- Dry skin and sunken eyes, which tend to show up as dehydration gets worse.
Many of these symptoms have other causes too, so use them as a prompt to drink something, not as a diagnosis. If they do not improve once you rehydrate, check in with a health professional.
What causes dehydration?
Anything that makes you lose fluid faster than you replace it. MedlinePlus lists:
- Diarrhea or vomiting.
- Heavy sweating from heat or exercise.
- Fever.
- Urinating a lot, which some medicines and illnesses cause.
- Simply not drinking enough water or other fluids.
On a busy day it is the last one that catches most people. You get absorbed in work, and by the afternoon you have barely had a glass. If that sounds like you, our guide on how to remember to drink water during a busy workday can help.
Who is at higher risk?
The NHS says some people become dehydrated more easily (NHS):
- Babies, children and older adults.
- People with diabetes.
- Anyone who has been sick or has had diarrhoea.
- People who have been in the sun or a hot place too long, or who sweat a lot when they exercise.
- People with a high temperature.
- People who have drunk too much alcohol.
- People taking diuretics, which are medicines that make you pee more.
- People who rely on others to get them drinks.
When is dehydration an emergency?
Mild dehydration usually improves when you drink fluids. Severe dehydration does not, and it needs medical care. MedlinePlus lists these as severe signs that need emergency care:
- Confusion.
- Fainting.
- Little or no urine.
- A rapid heartbeat or rapid breathing.
- Signs of shock, such as pale, cold or blotchy skin.
The NHS says to get urgent help if you are unusually tired, feel dizzy when standing and it does not go away, have dark yellow pee or are peeing less than normal, or are breathing quickly or have a fast heart rate. Call emergency services if you also have confusion, difficulty breathing, blue, grey or blotchy skin, or you are very sleepy and hard to wake (NHS).
How to rehydrate
- Drink fluids steadily, mostly water, instead of gulping a huge amount at once.
- Take small sips if you feel sick. MedlinePlus suggests small sips of water or ice chips if you struggle to keep liquids down.
- Drink extra in hot weather, when you exercise or work outside, and when you are ill.
- Limit sugary drinks and caffeine, as MedlinePlus advises.
- Consider a sports drink if you have lost a lot of minerals through sweat, but note that some are high in sugar.
- Check your urine through the day and adjust. Pale yellow is the target.
How much water should you drink to prevent it?
A simple starting point is about half an ounce of water per pound of body weight, and more when it is hot or you are active. We explain the numbers in how many ounces of water you should drink a day and how much water you should drink a day.
Make staying hydrated automatic
The easiest way to avoid dehydration is to stop relying on thirst and memory. A water tracker does the remembering for you.
- Log a glass in a tap, on your iPhone or Apple Watch.
- See your day at a glance as a ring, so you know if you are behind.
- Get gentle reminders through the day, which stop once you have reached your goal.
- Set your own goal, or take a suggestion based on your weight, activity and climate.
Download Hydrabit on the App Store. It is free to use, has no account, and keeps your data on your device. Hydrabit is a tracking tool and does not provide medical advice.
Frequently Asked Questions
The bottom line
Dark urine, a dry mouth, a headache and tiredness are your body asking for fluid. Drink steadily through the day, keep your urine pale, and know the warning signs that need medical help.
Pick your goal, log your glasses and let reminders do the remembering. Download Hydrabit to get started.
