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.­­

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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.

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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).

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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.

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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.

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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.

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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.

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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.”

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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.

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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.

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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.

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.