What happens to your body when you’re dehydrated

Analysis by Dr. Joseph Mercola Fact Checked

drinking glass of water

Story at-a-glance

  • Dehydration happens when you’ve lost too much water in your body without replacing it, which prevents your body from performing its normal functions
  • Beverage companies claim that sports drinks will help replenish the electrolytes in your body during exercise or outdoor activities, but the truth is the ingredients of your favorite sports drinks will not hydrate and benefit you, and may even be detrimental to your health
  • When you nourish your body with structured water, you are restoring your body to a balanced and whole state


This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.

Dehydration is a health concern that should never be ignored. Anyone can become dehydrated for various reasons, so it is important that you always hydrate yourself with filtered water. Read on to learn more about symptoms of dehydration and how you can prevent it.

What is dehydration?

Dehydration happens when you've lost too much water without replacing it, preventing your body from performing its normal functions.1 Remember that water makes up nearly 50% to 60% of your body, depending on your gender.2 It plays a large part in many bodily functions, such as lubricating your joints and retaining moisture in your eyes, keeping your skin healthy, eliminating toxins and facilitating proper digestion.

Proper intake of fluids is also vital for kidney function3 so, every time your body loses water, you need to replace those fluids to maintain balance between the salts, glucose and other minerals in your system.4

If you become dehydrated, drastic changes in your body can immediately occur. Research has shown that even mild dehydration can decrease brain tissue fluid, which can result in changes in brain volume.5 Your blood becomes more viscous as well, straining your cardiovascular system and putting you at risk of health issues like thrombogenesis.6 Dehydration also compromises your body's ability to regulate your temperature.7

Losing just 1% to 2% of your entire water content can cause thirstiness, a sign that you need to replenish the lost liquids.8 Mild dehydration can easily be treated but if it reaches extreme levels, it can be life-threatening and will require immediate medical attention.

Signs and symptoms of dehydration

Here are the mild and severe symptoms of dehydration, according to the Mayo Clinic:9

Mild to moderate dehydration

  • Dry, sticky mouth
  • Sleepiness or tiredness
  • Dry skin
  • Headache
  • Constipation
  • Dizziness or lightheadedness
  • Few or no tears when crying
  • Minimal urine
  • Dry, cool skin10
  • Muscle cramps

Severe dehydration

  • Extreme thirst
  • Irritability and confusion
  • Sunken eyes
  • Dry skin that doesn't bounce back when you pinch it
  • Low blood pressure
  • Rapid heartbeat
  • Rapid breathing
  • No tears when crying
  • Fever
  • Little or no urination, and any urine color that is darker than usual
  • In serious cases, delirium or unconsciousness

Infants and children are more vulnerable to dehydration. HealthyChildren.org notes that immediate attention must be given to these age groups if they exhibit the following symptoms:11

Mild to moderate dehydration

  • Urinates less frequently (for infants, fewer than six wet diapers per day)
  • Plays less than usual
  • Parched, dry mouth
  • Fewer tears when crying
  • Sunken soft spot on the head (fontanelle)
  • Loose stools (if dehydration is caused by diarrhea). If dehydration is due to fluid loss, there will be fewer bowel movements

Severe dehydration

  • Very fussy
  • Excessively sleepy
  • Sunken eyes
  • Cool, discolored hands and feet
  • Wrinkled skin
  • Urinates only once or twice a day

Chronic dehydration can affect your organs and lead to kidney stones,12 constipation13 and electrolyte imbalances that may result in seizures.14 Whether it is mild, moderate or severe dehydration, the liquids lost from your body must be immediately replaced. If you become dehydrated and begin experiencing symptoms like those mentioned here, get professional treatment as soon as possible.

What causes dehydration?

There are various reasons why dehydration occurs, and the causes can be a result of both losing too many fluids and not taking in enough. For example, intense physical activity can cause you to sweat profusely and lose substantial amounts of water, so proper hydration is necessary to replenish what you've lost. Medical News Today says other causes of dehydration include:15

  • Diarrhea — This condition prevents your intestinal tract from absorbing water from the foods that you eat, making it the most common cause of dehydration.
  • Vomiting — Common causes include foodborne illnesses, nausea and alcohol poisoning.
  • Sweating — Vigorous sweating may occur for various reasons, such as if you have a fever, work in hot environments or engage in intense physical activity.
  • Diabetes Having high blood sugar levels can cause frequent urination and, subsequently, extreme loss of fluids in your cells, leading to dehydration.
  • Frequent urination — Nondiabetics may urinate frequently because of alcohol intake or from taking certain drugs like antihistamines, blood pressure medications and antipsychotics. Too much caffeine intake can cause you to urinate more frequently, too.16

Who is at risk of dehydration?

Everyone is prone to dehydration, but some people have a higher risk for it, such as those who engage in strenuous exercise. One example is mountain climbing. It is especially hard for hikers to stay hydrated because the pressure at high altitudes makes them sweat more and breathe harder.17

Professional athletes, particularly those who compete in marathons, triathlons and cycling tournaments, are also predisposed to dehydration. Research suggests that even low levels of dehydration can impair athletes' cardiovascular and thermoregulatory response.18

One study even revealed that dehydration can impair basketball players' performance. The study focused on 17 males ranging from 17 to 28 years old, and determined their performance based on different dehydration levels of up to 4%. The result showed that when there's an increase in dehydration, skill performance decreases.19

Infants are especially prone to dehydration since their bodies are composed of 78% water at birth, dropping to about 65% by age 1.20 Since their bodies are more vulnerable to water depletion, their need for water is greater than adults.

Elderly people are also at risk for dehydration since the thirst mechanism weakens as a person grows older. According to a 2016 study,21 20% of seniors are not getting enough water every day due to several causes, ranging from forgetfulness to a desire to fight incontinence by consuming fewer fluids, to simply being too frail to care for their personal needs.

Those who have chronic diseases that cause frequent urination such as diabetes or kidney problems have an increased risk of dehydration.22 If you have a chronic illness that causes dehydration, make sure to take the necessary steps to hydrate yourself at all times to protect your health.

How to prevent dehydration

Water plays such an immense role in your bodily functions, making it an essential part of your everyday life. Since dehydration can be life-threatening, it is important that you replenish your body with water immediately if you feel yourself becoming dehydrated.

Always bring water with you during exercise or any physical activity, especially when the temperature's too hot. One good rule of thumb to prevent dehydration is to drink as much water as it takes for your urine to turn light yellow. Dark urine means that your kidneys are retaining liquids in an effort to have enough for your body to perform its normal functions.

It is especially important to pay attention if you are sick with fever, are vomiting or have diarrhea, so you don't become dehydrated. Be sure to drink enough water to replace the liquids that you've lost. If you are vomiting or have diarrhea to the point that you can't drink enough to stay hydrated, you may need to visit an emergency department for help in maintaining hydration.

Sports drinks and other sweetened beverages will not keep you hydrated

Sports drinks are one of the most commercialized beverages today — from TV advertisements to popular athlete endorsers, mainstream media make it look like sports drinks are the answer to keeping you healthy and well-hydrated.

Beverage companies advertise that these drinks will help replenish the electrolytes in your body during exercise or outdoor activities, but the truth is the drinks with actual science studies behind them were created for high-performance athletes who deplete their water stores quickly, not for the average person looking to address thirst issues.

Indeed, downing too many of these drinks may even be detrimental to your health — particularly if they fall in a class of beverages known as "energy" drinks.23

A typical sports or energy drink contains high amounts of citric acid. According to a 2017 study from The Science Journal of the Lander College of Arts and Sciences, drinking sports or energy drinks that have citric acid can chip away the enamel in your teeth faster, leading to dental erosion.24 Sports drinks like Powerade and Gatorade also come loaded with sugar — a BMJ study25 reported 19 grams and 30 grams, respectively, for a 500 mL (about 17 ounces) bottle of these two beverages.

Aside from sports drinks, there are other sweetened beverages that won't give you any benefit, like sodas. These are equally unhealthy for you, as a 20-ounce bottle of cola gives you 16 teaspoons of sugar, usually in the form of high-fructose corn syrup.26

Energy drinks come with their own set of problems: Consumed by 30% to 50% of adolescents and young adults, these drinks are supplemented with ingredients hyped as energy boosters. From dangerous levels of caffeine to taurine to herbs and various sugars, what's in these drinks can cause "seizures, mania, stroke and sudden death" when consumed, and are a risk especially for anyone who is diabetic, has a heart, thyroid or kidney disease, or is taking certain medications.27

Commercial fruit juices are another group of heavily processed sweetened drinks that have too many sugars and not enough value to make them useful for hydrating purposes. For example, a 12-ounce can of Minute Maid's 100% Apple Juice contains 37 grams of sugar,28 which can put you at risk of diabetes, weight gain and obesity.

Choose to drink living water

If you're on a community water system, don't just turn on the tap and fill a glass or water bottle, as it may very well contain fluoride, as well as heavy metals and disinfection byproducts that can have ill effects on your health. Installing a water filter in your home, both at the tap and preferably also at the point of entrance, can help eliminate these harmful contaminants.

If you want the best water for you and your family, I suggest drinking structured or "living" water, such as deep spring water. According to Gerald Pollack, one of the world's leading research scientists on the physics of water, structured water or EZ "exclusion zone" water is the same type of water found in your body's cells. It has a negative charge, and works just like a battery by holding and delivering energy.

Since distilled water is too acidic and alkaline water is too alkaline, you should nourish your body only with structured water, as it contains the ideal PH range of 6.5 to 7.5, which enables your body to maintain a balanced and whole state.

I personally drink vortexed water since I became a fan of Viktor Schauberger, who did so much work regarding vortexing many years ago.29 By creating a vortex in your glass of water, you are putting energy into it and increasing EZ as well.

Ideal EZ water can be found in glacial melt, but since it is practically inaccessible for almost everyone, natural deep spring water is a good source. When storing water, use glass jugs and avoid plastic bottles since they contain bisphenol A and phthalates, which are linked to health issues, such as sexual dysfunction and disruption of thyroid hormone levels.30,31

Other natural thirst-quenchers for preventing dehydration

If you want to drink something more flavorful than water, you can opt for raw, organic green juice made from fresh vegetables. However, I recommend refraining from drinking juice with too many fruits as it will have high amounts of sugar and calories. Go for a green juice recipe that combines one or two fruits only and larger amounts of greens like spinach, celery or kale. That way, you can minimize your sugar intake and still get all the nutrients from the fruits and vegetables in their purest forms.

I advise keeping your fructose consumption below 25 grams per day. If you have Type 2 diabetes, insulin resistance or heart disease, it is wise to minimize your total fructose to 15 grams daily, including that from fruits.

Coconut water serves as a great replacement for sports drinks. It provides optimal health benefits due to its anti-inflammatory32 and antioxidant33 effects. A word of caution: Coconut water also contains sugar, albeit in smaller amounts compared to other fruits, so drink it in moderation, preferably after a cardio workout, when you need to replace minerals and fluids.

The key to avoiding dehydration: Listen to your body

No one but you can determine if you are hydrated enough. If you feel thirsty or you're sweating profusely, this is a signal that you need to replenish your body with water immediately. Don't wait for severe dehydration symptoms to occur before you take action, since this can be life-threatening.

Since anyone can become dehydrated even without any physical activity, keeping a bottle of filtered water nearby can help keep you hydrated. Remember that a healthy person should urinate seven to eight times each day, so if you're not urinating frequently it means you're not drinking enough water.

Remember: Nothing feels more refreshing than drinking cool water to replace the liquids that you've lost. It's also important to always listen to your body. Once you feel that urge to drink, opt for structured or filtered water rather than artificially sweetened beverages, which can have negative effects on your health.

+ Sources and References

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