How to check if you are dehydrated

Dehydration occurs when you don't have enough fluids in your body. If severe, dehydration can cause serious problems. If you suspect you are (or someone else is) severely dehydrated, seek medical attention.

You are dehydrated if your body doesn't have enough water to keep it working properly. It can happen when your body loses too much fluid, such as from excessive sweating.

What are the signs and symptoms of dehydration?

If you have mild to moderate dehydration, you might:

  • be thirsty
  • have a dry mouth, lips and tongue
  • have a headache
  • have dark urine, and not so much of it
  • be dizzy or light-headed, particularly when standing up

If you have severe dehydration, you might:

  • be extremely thirsty
  • have a very dry mouth
  • be breathing fast
  • have a fast heart rate and a low blood pressure
  • have a fever
  • have little or no urine
  • be irritable, drowsy or confused

How to check if you are dehydrated
Use this urine colour chart to assess how hydrated you are.

Dehydration in babies and young children

Babies and young children have a higher risk of becoming dehydrated than adults, especially if they are sick. A baby or young child can quickly become dehydrated if they are vomiting or have a fever or diarrhoea. As well as those listed above, signs of mild dehydration in babies and toddlers include fewer wet nappies or nappies not as wet as usual. Older children will not go to the toilet as often.

Babies who are severely dehydrated have a sunken fontanel, the soft spot on top of a baby’s head.

If your baby or young child shows signs of severe dehydration or you are concerned for any reason, see your GP or go to the nearest emergency department.

Dehydration in older people

Older people can become easily dehydrated because of:

  • declining kidney function
  • chronic illness
  • limited mobility
  • medication

Dehydration in the elderly can cause problems such as confusion, constipation, dizziness and weakness. Elderly people need to keep up their fluid intake – they may become dehydrated before they feel thirsty. If you’re caring for an elderly person, you may need to remind them to drink regularly.

What causes dehydration?

People can get dehydrated:

Anyone may become dehydrated, but babies, young children, older adults and people with long-term illnesses are at most risk.

How is dehydration treated?

If you are mildly dehydrated, the best thing you can do is to drink more water. Drink small amounts of water regularly. You can also drink oral rehydration solutions purchased from the pharmacy or make your own (6 teaspoons of sugar with half a teaspoon of salt in one litre of boiled water). Here are instructions. Avoid alcohol and caffeine, as they can make you more dehydrated.

When should I see my doctor?

Severe dehydration needs immediate medical treatment, usually in hospital where fluids are given through an intravenous drip.

If you, your baby, child or elderly relative is severely dehydrated, you need to seek urgent medical attention. See your doctor or go to a hospital emergency room.

Can dehydration be prevented?

Make sure you drink enough water each day, and have extra to replace any fluid lost during hot weather, illness or exercise. Water is the best drink to hydrate the body. As a general guide, adults should drink around 2 to 2.5 litres of fluid a day and children should drink around 1 to 2 litres a day.

Resources and support

For more information and support, try these resources:

Medically Reviewed by Minesh Khatri, MD on May 20, 2021

  • Causes
  • Symptoms
  • Who’s at Risk?

Dehydration happens when your body doesn't have as much water as it needs. Without enough, your body can't function properly. You can have mild, moderate, or severe dehydration depending on how much fluid is missing from your body.

It’s normal to lose water from your body every day by sweating, breathing, peeing, and pooping, and through tears and saliva (spit). Usually you replace the lost liquid by drinking fluids and eating foods that contain water. If you lose too much water or don’t drink and eat enough, you can get dehydrated.

You can lose more water than usual with:

You may not replace the water you lose because:

  • You’re busy and forget to drink enough.
  • You don’t realize you’re thirsty.
  • You don’t feel like drinking because you have a sore throat or mouth sores, or you’re sick to your stomach.

Signs of mild or moderate dehydration include:

Signs of severe dehydration include:

  • Not peeing or having very dark yellow pee
  • Very dry skin
  • Feeling dizzy
  • Rapid heartbeat
  • Rapid breathing
  • Sunken eyes
  • Sleepiness, lack of energy, confusion or irritability
  • Fainting

Symptoms for babies and young children can be different than for adults:

  • Dry mouth and tongue
  • No tears when crying
  • Dry diapers for 3 hours
  • Sunken eyes, cheeks, soft spot on the top of the skull
  • Sleepiness, lack of energy, or irritability

Severe dehydration is a medical emergency and needs to be treated immediately.

Anyone can get dehydrated, but the odds are higher for some people:

  • Babies and young children are the most likely to have severe diarrhea and vomiting, and they lose the most water from a high fever. The youngest can’t tell you they’re thirsty or get their own drink.
  • Older adults often don’t realize they’re thirsty. If they can’t get around very well anymore, they may not be able to get a drink easily or may not be able to take in enough fluids due to medical conditions.
  • People who are ill with a cold or sore throat may not want to eat or drink.
  • People with a chronic disease such as type 1 or type 2 diabetes can pee a lot if the disease is uncontrolled. They also may take medicines such as water pills, which make them go more often.
  • People who are active outside in hot and humid weather sometimes can’t cool down effectively because their sweat doesn’t evaporate. This can lead to a higher body temperature and need for more water.

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Becoming extremely dehydrated — defined by the World Health Organization as losing more than 10 percent of your body weight in fluid — can lead to injury or fatal complications, and it requires an ER visit. Seizures, cardiac arrhythmia, or hypovolemic shock can occur because your blood volume is too low.

Yet it rarely comes to that. Most of the time, you can easily replenish your fluid stores and fend off dehydration. The truth is you can lose 3 to 4 percent of your body weight through dehydration without feeling any real symptoms, says Alp Arkun, MD, the chief of service for emergency medicine at the Kaiser Permanente Fontana and Ontario Medical Centers in Southern California. Yet, once you have lost 5 to 6 percent, you’ll start to feel the symptoms of mild dehydration, notes MedlinePlus. Thirst, fatigue, dizziness, or constipation are sure signs it’s time to reach for water or a sports drink that’s low in sugar and high in electrolytes.­­

RELATED: Thirsty? 9 Refreshing Alternatives to Soda

But the signs of dehydration aren’t always so obvious. Here are six surprising signs and symptoms of dehydration.

1. Bad Breath Is a Possible Warning Sign of Dehydration

Saliva has antibacterial properties, but dehydration can prevent your body from making enough saliva.

“If you’re not producing enough saliva, you can get bacterial overgrowth in the mouth, and one of the side effects of that is bad breath,” says John Higgins, MD, a professor of medicine at the University of Texas in Houston and the chief of cardiology at Lyndon B. Johnson General Hospital in Houston.

It’s the same reason you may wake up with “morning breath”: Saliva production slows down during sleep, notes the Mayo Clinic, leading to an unpleasant taste in the mouth as bacteria grow. So the next time your mouth seems dry and your breath smells less-than-fresh, it may be time to rehydrate.

RELATED: What Is ‘Raw’ Water, and Should You Drink It?

2. Dry or Flushed Skin Could Be a Symptom of Dehydration

“A lot of people think that people who get dehydrated are really sweaty, but in fact, as you go through various stages of dehydration, you get very dry skin,” Dr. Higgins says, adding that skin may appear flushed as well.

Another key skin-related symptom of dehydration is skin that remains “tented” after being pinched and takes some time to return to its normal, flat appearance (more on that below).

RELATED: 10 Surprising Causes of Dry Skin

3. Muscle Cramps Are a Dehydration Symptom, Likely From Heat Illness

When your body loses enough fluid, it’s unable to cool itself off adequately, leading to heat illness, notes OrthoInfo. One symptom to look out for is muscle cramps, which can happen while exercising, particularly in hot weather.

“The hotter you get, the more likely you are to get muscle cramps, and that’s from a pure heat effect on the muscles. As the muscles work harder and harder, they can seize up from the heat itself. Changes in the electrolytes, such as sodium and potassium, can lead to muscle cramping as well,” says Higgins.

Bear in mind that when it comes to rehydration after exercise, all drinks may not be created equal. A study published in March 2019 in the BMJ Open Sport and Exercise Medicine found that when participants rehydrated with a drink containing electrolytes after exercise, they were less likely to develop muscle cramps. Participants who drank plain water, on the other hand, were more likely to have cramps. The study was small, so its findings may not apply to you, but the next time you feel a muscle cramp coming on after exercise, opting for an electrolyte-filled sports drink may help.

Even in cooler weather, dehydration is possible if you don’t drink enough fluids while working out. Higgins says symptoms may be milder or come on slower, but dehydration carries the same risks, regardless of the temperature outside.

4. Fever and Chills Are Symptoms of Heat Illness, Which Causes Dehydration

Other symptoms of heat illness include fever and chills. You may sweat profusely while your skin is cool to the touch.

Fever can worsen dehydration. The higher the fever, the more dehydrated you may become. Unless your body temperature decreases, your skin will lose its cool clamminess and then become hot, flushed, and dry to the touch. At this point, it’s important that you cool yourself down immediately and see a medical professional, the Centers for Disease Control and Prevention (CDC) advises. Applying ice and cool, wet cloths, and moving to a cool area are short-term strategies until you can see a medical professional.

According to the Mayo Clinic, children and infants lose more of their body fluid to fever, and they are more likely to experience severe diarrhea and vomiting from illness. Any fever in an infant or toddler is cause for concern. Ask your pediatrician for guidelines on when to call for help.

The CDC urges adults with fever to seek medical help if their temperature reaches 103 degrees F.

RELATED: 6 Smart Tips for Staying Hydrated Throughout the Day

5. Food Cravings, Especially for Sweets, May Just Mean You’re Thirsty

“When you’re dehydrated, it can be difficult for organs such as the liver, which uses water, to release glycogen [stored glucose] and other components of your energy stores, so you can actually get cravings for food,” Higgins says.

While you can crave anything from chocolate to a salty snack, cravings for sweets are more common because your body may be experiencing difficulty breaking down glycogen to release glucose into the bloodstream to use as fuel, he says.

6. Headaches Could Be a Sign You Need to Drink More Water

As MedlinePlus points out, even mild dehydration can cause a dehydration headache and trigger a migraine headache. Although various factors besides dehydration can cause headaches, drinking a full glass of water and continuing to sip more fluids during the day is an easy way to ease your pain if, in fact, dehydration is a culprit.

RELATED: What Is Alkaline Water and Does It Offer More Benefits Than Plain H2O?

How to Tell if You’re Dehydrated or if It’s Something Else

If you’re thirsty, you’re already dehydrated. But lack of thirst doesn’t necessarily mean you’re well hydrated. Here are two other ways to check whether your body is dehydrated:

Try this skin test. Use two fingers to pinch up some skin on the back of your hand, and then let the skin go. The skin should spring back to its normal position in less than a couple of seconds. Higgins says that if the skin returns to normal more slowly, you might be dehydrated.

Check your urine. If you’re well hydrated, your urine will be mostly clear with a tinge of yellow (the color of light lemonade before it hits the bowl). Darker yellow or orange are the “warning” colors to watch for, per UC San Diego Health. If you see those colors, start drinking fluids.

RELATED: 8 Foods High in Water That Can Help Prevent Dehydration

Tips for Staying Hydrated

When it comes to daily water intake, hard-and-fast rules are difficult to apply because it depends on so many variables, including your age, gender, whether you’re pregnant or breast-feeding, and whether you have any underlying medical conditions.

Yet 2004 guidelines from the National Academies of Sciences, Engineering, and Medicine — the most recent available — advise that getting 2.7 liters per day for women and 3.7 liters per day for men. You can reach this amount by consuming foods and fluids.

Here are some tips for getting all the fluids you need and avoiding dehydration:

Keep Your Water Bottle Handy at All Times

“If it's right next to you, you'll likely get into the habit of sipping it without even realizing it,” says Johannah Sakimura, RD, an outpatient oncology dietitian at Overlook Medical Center in Summit, New Jersey.

RELATED: The Best Water Bottles to Keep You Hydrated

Try Spicing Up Plain Water

“If you don't love plain water, jazz it up by adding a splash of fruit juice or chunks of fresh or frozen fruit,” says Sakimura. “Or try naturally flavored, calorie-free seltzers — their fizz and fruit flavor makes them more appealing than plain, flat water.”

RELATED: LaCroix Lawsuit: Is Sparkling Water Good or Bad for You?

Turn to Sugar-Free Herbal Tea or Coffee

Sakimura recommends drinking unsweetened teas, which are available in lots of different flavors. “Sip fruity iced teas during the day (with lots of ice if it's hot out), or cozy up with a mug of hot peppermint or chamomile tea at night — they all count toward your daily fluid goal.” And if your beverage of choice is coffee rather than tea, that works, too: While caffeinated drinks may have a diuretic affect, increasing your need to urinate, one crossover study of 50 men found that there were no significant differences in total hydration when the men drank four cups of coffee daily compared with four cups of water. The results of the study, which were published in the journal PLoS One in January 2014, suggest that coffee hydrates similarly to water when consumed in moderation by regular coffee drinkers.

RELATED: Is Filtered Coffee Healthier Than Unfiltered Coffee?

Swap Your Packaged Snacks for Fresh Options 

“Swap dry snacks, like chips, pretzels, and crackers — which have a very low water content — with refreshing munchies, like fresh or frozen fruit, yogurt, healthy smoothies, celery with peanut butter, and cut veggies with hummus,” recommends Sakimura.

Pile on the Produce 

In the same vein, know that those veggies and fruits are hydrating, just like beverages. “Aim to make half your plate produce at meals. All those vegetable and fruit servings will supply water as well as a hearty dose of vitamins, minerals, and fiber,” says Sakimura. “In fact, some fruits and vegetables are more than 90 percent water — including cantaloupe, strawberries, watermelon (of course), cucumber, celery, lettuce and leafy greens, zucchini, tomatoes, and bell peppers.”

Sip More Fluid During Meals

“Sipping water with meals will help you eat more slowly, pace your eating, and, of course, stay hydrated,” Sakimura says. Drinking water before eating may furthermore help with weight loss, as it did for participants of a study published in the journal Obesity in August 2015. During a small randomized controlled trial involving 84 subjects, participants who drank 500 milliliters (ml) of water 30 minutes before eating lost an average of 1.3 kilograms (kg) at the 12-week follow-up.

RELATED: 5 Tricks for Getting Enough Fruit and Veggies

A Final Note on the Importance of Preventing Dehydration if You’re Elderly

Elderly people may be at higher risk for dehydration for a number of reasons, per the National Academies of Sciences, Engineering, and Medicine.

Some elderly people become chronically dehydrated if they take certain medicines, such as diuretics, have a diminished sense of thirst, are not able to get themselves a glass of water easily, or forget to drink because of dementia. Chronic dehydration in an elderly person may lead to confusion, low blood pressure, dizziness, and constipation.

If you have an elderly relative with mobility limitations or cognitive problems, be sure to watch him or her for signs of dehydration, or ask their caregivers to do so. Certain prescriptions can be costly, so make sure to know your Medicare coverage options.

As for your own well-being, remember that healthy bodies are composed of at least 60 percent water, notes the U.S. Geological Society. Keep that healthy balance, and drink up!

Additional reporting by Sheryl Huggins Salomon and Laura McArdle.