Updated September 10, 2020
An overview of what dehydration is, how it affects the body, and a detailed explanation of what happens to your body as you become dehydrated.
Join us for a comprehensive breakdown of dehydration, from what it is, and how it’s caused to who is most at risk of developing dehydration, how it kills you, and what symptoms to look out for before it gets too bad. In order to be as detailed as possible, we’ve even included some information on compounding illnesses and conditions that can bring about or exacerbate dehydration.
Once we’ve explained what dehydration is and how to avoid it in general terms, we’ve included our dehydration timeline that explains each of the four stages of dehydration in more detail. We’ve detailed how much weight in moisture you’ll lose at each stage and how this affects certain organs, producing the symptoms we associate with each phase of dehydration.
If you have any questions about dehydration that aren’t answered here, check out the bottom of the page where we’ve answered some of the most common questions that get asked online.
Before we can explain the ins and outs of dehydration, we first need to explain what it is in general terms. Dehydration means that your body, whether it’s naturally throughout the day or through actions like exercise or sweating in warm weather, loses more fluids than are taken in through food and drink.
In essence, it’s when you are being starved of liquid. Avoiding dehydration is actually more important since, as a general rule, humans can survive three weeks without food but barely one week without water. Water is the main reason that life developed on Earth, after all.
Water makes up 55% to 65% of your body, depending on your build, with the important parts like your heart and your brain being made 73% to 75% water. Without water, your brain struggles with thinking, your muscles tense up, and the blood in your veins struggles to flow through your body, but we’ll go deeper into the symptoms of dehydration later.
So, your hydration isn’t something to take lightly. You’d be surprised by how many people don’t get the recommended amount of water a day. You know the deal, follow the 8×8 rule. That’s eight eight-ounce glasses of water a day to keep dehydration at bay.
Since dehydration is usually caused by either an inconsistent intake of liquids or a compounding issue that limits your water consumption, it’s no surprise that the most at-risk demographics are babies, children, and the elderly. Here we’ll go into why these groups suffer more often, as well as why athletes and those who live in hot climates are prone to dehydration too.
Infants and children not only lack autonomy on what they consume, but they are also the most likely to experience diarrhea and vomiting brought on my other issues. These symptoms will be coming up later in this piece as they’re an important step in the path to dehydration.
As you get older, your fluid reserves get smaller and it becomes more difficult to conserve water in your system. As your senses dull, so too does your sense of thirst. Add chronic illnesses like diabetes and dementia into the equation and you’re looking at a recipe for dehydration. The elderly in particular might struggle with their mobility, so getting water for themselves becomes difficult, presenting a similar problem to how infants can’t get their own water.
Barring the oldest and the youngest members of society, the others most at risk of dehydration are those who work and exercise outside. This is made worse if you’re in a hotter country, of course, but generally, people who work outside and exercise regularly will lose a lot more fluid through sweat than a relatively inactive person.
By explaining how certain groups are more at risk, we’ve already covered some of the things that cause dehydration, like a lack of the ability to get your own water, chronic illnesses and water-losing symptoms, and time spent outside in hot weather or performing activities that result in you sweating more.
Those are just some of the causes, however, and there are some more that apply to most people that you should be aware of. We mentioned how diarrhea and vomiting are symptoms that cause the loss of fluids in the body, resulting in dehydration. There are more examples of these kinds of symptoms that can be caused by lifestyle habits or other illnesses unrelated to dehydration.
Besides vomiting, diarrhea, and sweating, two to look out for are fevers and an increase in how much you urinate. Fevers cause more sweating anyway, which removes fluid and electrolytes from your body, whilst also increasing your temperature. This means that the fluid that is in your body doesn’t last as long as it would in more temperate conditions. You’re also less likely to eat and drink, limiting your fluid intake.
Following this line of logic, other illnesses that can cause a sore throat, mouth sores, stomach pains, and other uncomfortable symptoms related to the actions of eating and drinking can also be causes of dehydration if they stop someone from drinking.
An increase in urination is self-explanatory. Urination is our way of purging many substances from our body, and we do it through releasing a stream of fluids, so more urination can cause dehydration if you’re not drinking enough to account for it. Be careful with what you are drinking, however, as caffeinated drinks are diuretics that cause you to urinate more. If you’re drinking a lot of coffee, you should be drinking more water to back it up. Uncontrolled diabetes and blood pressure medications can also be the cause of urine increase.
To get into specifics, here are some food and drinks that encourage dehydration. Asparagus is known to be a powerful diuretic, increasing your urine output and so the amount of fluid being lost every time you go for a pee. Cured meats and fried foods are packed with salt and, whilst sodium may be amongst the electrolytes needed to maintain balanced hydration, it’s not great to include too much of it in your diet.
An over-representation of protein, sodium, and sugar in your diet can make you more susceptible to dehydration. Sugar, and in particular sugary drinks, are tricky in that they confuse your thirst senses. The act of drinking and the liquidity of these drinks make your body think you’ve drunk, suppressing your thirst despite the fact they can have the opposite effect since sugar takes more water to process through your body. Stay away from drinking fruit juices and sports drinks too much if this is a problem for you.
We’ll be giving a full rundown of dehydration and its effects on your body below, but first, you should know the most common symptoms of dehydration. These are the symptoms you should look out for that are mostly associated with the first two stages of dehydration, because trust us, you’ll know if you’ve hit the third and fourth stages.
The obvious one is thirst. We have thirst sensors for a reason, to track our fluid levels and identify when they’ve fallen below the ideal volume. We’ve already mentioned how our thirst sense can become dulled with age, so it’s important to pay attention to your body and the signals it sends you, especially as you grow older.
If you’re busy or otherwise occupied and you start to feel thirsty, don’t ignore that thirst and drink water within the hour of feeling it. It doesn’t take long and we’re sure it’s more important than whatever you’re doing. Along with thirst, it’s common to get a dry mouth and tongue too. No one likes having a dry mouth, so it’s a great incentive to treat yourself to some cold water.
Besides thirst and a dry mouth, another common symptom of dehydration is a change to your urine. While passing urine more often can be a cause of dehydration, when dehydrated you may notice you’re urinating less often, and less urine is coming out when you do.
The other well-known urine symptom is a darkening of the urine. When you drink a lot of water, you may have noticed that your urine can be almost clear. This is because there’s more water content, so the excess materials being purged don’t have so much influence over the color of the urine. When that water is absent, however, you will have darker urine that’ll smell stronger too, so drink a lot of water for your nose’s sake.
As your dehydration progresses, you will get symptoms that extend beyond mild discomforts. These worse symptoms are headaches, dizziness, and fatigue, the ones that tell you that you’re becoming ill and are much harder to ignore than a dry mouth.
Dizziness, in particular, can be dangerous in the wrong circumstances, so it’s paramount that you get rehydrated as soon as possible. It can also come with confusion, another dangerous symptom that impairs your ability to do pretty much anything you could want to do, so you’d have nothing to lose and everything to gain by drinking water at this stage.
If you’re a parent or guardian and need to be on the lookout for dehydration symptoms in your little ones, we’ve got what you’re looking for right here. A lot of the symptoms for children are the same as those found in normal adults, but the difficulty comes in when your children cannot express that they are thirsty, so there are other signs to look out for.
A dry mouth is a good indicator, as are eyes and cheeks that appear sunken for no other discernible reason. Any discomfort in children is often expressed through irritability, becoming cranky and quick to anger or upset. Don’t assume they’re just tired, maybe they need some water.
Some of the more child-specific symptoms are a lack of tears if they do cry. It’s hard to make tears when your body is lacking in fluids and, since those fluids need to keep the heart and brain working, a child’s ability to leak tears when they cry may be one of the first things to go. They may also forego urination, not wetting their diapers for a period of three hours or more. Waiting three hours is advised since you don’t want to raise any false alarms and over-hydrate your child.
If your child is still less than two years old, you might be able to pay attention to the soft spot on its head. This one probably isn’t the greatest for the squeamish readers out there, but babies have soft spots called fontanels on their heads so that the skull can adapt to brain growth. The one at the top is known to either bulge or sink, depending on the emergency that’s affecting your child.
If your baby is well-hydrated, their fontanel will be firm and relatively flat. If it’s bulging, there may be a pressure buildup that requires a doctor’s eyes immediately. If it’s sunken, however, that can be a sign that your baby isn’t getting enough fluids.
These are some of the symptoms that warrant a visit to the doctor, no matter your age. A rapid heartbeat and breathing, which you may have felt before, may need a doctor’s checkup if you have had it for a prolonged period. It may be related to a lack of hydration on your part.
One of these symptoms is having a stool that’s either bloody or black in color. This can be a sign that your dehydration has advanced to a critical stage, at which point you should see a doctor. They can also be symptoms of other serious conditions, so you lose nothing by getting this checked on. Speaking of stool, if you’ve had diarrhea for longer than 24 hours, it’s also best to visit your doctor to get some medical-grade solutions. Diarrhea itself can be both a symptom of severe dehydration and, as covered above, an exaggerating factor in bringing about dehydration. Either way, it’s not a symptom you want to endure for over 24 hours.
Prolonged tiredness and irritability, as we’ve described above, can also be signals that it’s time to get medical help. Suffering from these behavior-altering symptoms isn’t healthy, not just for your body but your mental state too. We don’t make many decisions that we don’t regret when we’re irritable, tired, or completely disoriented, so it’s best to talk to your doctor to get you back to your old self.
The last dangerous symptom of dehydration is an ironic one, the inability to keep down fluids. If any fluids you drink come right back up afterward, then something could be wrong with you. Whether it’s as a result of the nauseous feeling that severe dehydration can cause or it’s a compounding factor that’ll make your dehydration worse, you should get the attention of your local doctor to stop this from happening.
The fatal consequences of dehydration are often referred to as “complications” in what we would call an understatement. These are failures of certain body parts that cause you to die. In the end, this is because you didn’t stay hydrated and this is why every creature alive, including plant matter, requires some of that sweet sky nectar if they want to live a long and happy life.
Heat injury is possible when you advance to the latter stages of dehydration, which is where your body stops regulating its own temperature and slowly increases. If this body temperature gets too high, you can get heat cramps, exhaustion, and even heat stroke. The intensity of heat injuries is only made worse if you happen to be dehydrated in a dry, hot climate.
Heatstroke is characterized by a state of confusion and disorientation combined with a strong feeling of sickness, so it becomes harder to eat and drink up the nutrients that you desperately need. If left untreated, heatstroke can cause you to die, either from exposure to harsh climates or from internal temperature deficiencies like those caused by dehydration.
The prime function of your kidneys is to purge waste and toxins throughout your body and transform it into the urine, ready to be sent out of your body when you can find the next toilet. Well, if you’re dehydrated, your kidneys don’t have much to do. Your blood pressure plummets when you’re dehydrated, meaning your kidneys get deprived of blood and stop working as efficiently. This means that they neglect their duties, letting debris and toxins gather in your blood. Your blood quickly becomes concentrated and toxic, hardening in your veins and leading to death.
Electrolytes are called electrolytes because they’re valuable minerals, like potassium and sodium, that carry electrical signals across your body. It’s essentially one of the many ways that cells communicate with one another. When electrolytes start getting scarce inside your system, however, your muscles can struggle with their absence, twitching and spasming. If these cell twitches happen in areas more important than your limb muscles, it can even result in fainting and periods of unconsciousness that can threaten your life.
Hypovolemic shock, also known as low blood volume shock, is one of the more serious causes of death that can ultimately be blamed on dehydration. We mentioned how dehydration causes kidney failure in this segment already, which is tied to low blood pressure in your vein system.
Hypovolemic shock is what happens when it’s the low blood volume that gets you first instead of the kidney failure. The drastic drop in pressure slows your blood to a crawl, so it’s not transporting oxygen around your body. Oxygen is important for staying alive, so being deprived of it is a surefire way to find yourself dead.
Whether it’s from one or a combination of the above symptoms of dehydration, it’s possible that you’ll slip into a coma. The blood toxicity, excessive body temperatures, and violent seizures possible with terminal dehydration can all be triggers for a coma. Entering a comatose state, if alone and suffering from dehydration, means death. If no one can find and administer some serious aid to bring you back to a healthy state, you’ll die. Even if you get lucky and get nursed back to health, there’s still a risk of brain damage that’ll diminish your quality of life.
Here’s a bonus risk that comes with dehydration that actually occurs after you’ve been dehydrated. Cerebral edema, commonly known as brain swelling, occurs when you’re receiving fluids again after having been dehydrated.
Cerebral edema is when your body has been starved of fluids for so long that, when it finally does get rehydrated, it binds too much fluid into the cells of your body. This causes cells to swell, sometimes to the point of rupturing. This isn’t much of a problem because most of your cells swell on a regular basis, and especially when they sustain an injury. Most.
If this swelling happens to take place in your brain cells, however, then it’s quite possible for you to sustain brain damage or even die from this swelling. This means that you essentially fall at the final hurdle, dying after suffering through the ordeal that is late-stage dehydration. What’s more, since the cell swelling was brought about by your previous state of dehydration, it means you’ve just died of dehydration after you’ve rehydrated.
Dehydration is a process, so when you’re dehydrated you fall into one stage of a multi-stage timeline that has many different symptoms and effects on your body. Here we’ve summarized each of the four main stages of dehydration so you can understand what dehydration looks like, from its minor first stage to its dangerous and even deadly third and fourth stages.
Mild Dehydration, or thirst, is the furthest most have us have ventured into the dehydration timeline. This is where you become conscious of any thirst that you have and, even though you don’t feel it, your body has started optimizing its water use so that no moisture in your body goes to waste.
This means that your kidneys send less water to the bladder, which is why your urine gets darker. Your body temperature rises since you don’t sweat as much anymore, and your heart rate increases to pump your now thicker blood through your body. That may sound extreme, but this is just the beginning. In reality, this will just feel like a dry mouth and fatigue.
This is just the start of the dehydration process and already there’s a lot going on inside you. What has happened here is that you’ve lost approximately 2% of your body weight. Assuming that you’re an average weight for the Western man, like 170 to 180 pounds, then that’s 3 to 3.6 pounds that you’ve lost. This may not sound like much, and it’s only as much as you would lose with an hour of high-intensity working out, but your body has noticed its absence and is telling you to drink it back.
So, what happens next if you don’t drink after feeling those thirst cravings? Moderate dehydration is where the dehydration process first becomes dangerous. We mentioned above how the blood starts to thicken when you get thirsty, and as dehydration advances, this problem only gets worse.
You’ve now stopped sweating, so your temperature is on the rise. The blood has now become too concentrated, decreasing blood flow and blood pressure, meaning you will faint if you don’t replenish your water. That’s where the danger comes in since now you can lose consciousness and fall into any number of dangerous situations.
Here you’ve lost twice as much a percentage of your body weight this time, you’re now 4% lighter. Again, assuming that you’re the American average, that’d be 7 to 7.2 pounds. If the first stage was an intense but otherwise stationary hour-long workout, this is an exercise bike for three hours in high heat, all with no rehydration going on.
Next, you’ll face severe dehydration, also called “organ damage” because that’s exactly what you can expect if you don’t reach for some water soon. The blood pressure of your body cannot be maintained and so, to ensure survival, blood retreats from the extremities of your body so that only the vital organs can keep functioning. Your kidneys and gut begin to deteriorate. You need those to survive in the long term, so your body has a funny definition of non-vital. Now that your kidneys are out of commission, they can’t filter your blood for cellular debris. You can develop shock when in this phase, too. You are now on your way to the final stage, and there are no prizes for guessing what that is.
Here you’ve lost up to 7% of your body weight, or 12 to 12.6 pounds if you weigh 170 to 180, which is a lot to lose through moisture alone. Now that your body is cordoning parts of itself off like a sinking ship, you’ll definitely be aware of that fact, too. This is the equivalent to working out as your day job, putting in eight hours of constant movement in a hot environment with no trips to the water cooler.
Next up is terminal dehydration or, not to put too fine a point on it, death. You need water or you will die, simple as that. At this point you have two options in how you’re going to die, which is two more than most people get, we suppose. Either it’s hot outside, and so the lack of temperature regulation in your body will overheat your organs to incite liver failure, or kidney failure will get you as too much debris builds up in your blood.
Since liver failure and kidney failure are their own problems with their own symptoms, we’ll detail a few here too since you’ll have to contend with them. If it’s a liver disease that you’re facing off against, you’ll be fatigued, nauseated, and you might develop diarrhea, which is the last thing you want when water retention is the key to survival. Jaundice will also develop, so your skin will yellow.
When dehydrating, acute kidney failure will cause shortness of breath, tiredness, blood in your urine, if you even have any left at this point. You’ll be weak, nauseated, and confused, maybe even to a point of delirium. The deadliest symptoms, short of dying of the failure itself, are seizures and/or entering a comatose state. Even if you got help afterward, suffering through a violent seizure or a comatose state can change your mental capacity, and not for the better.
Now you’ve lost up to 10% of your body weight, so 17 or 18 pounds if you’re at the weights we’ve been working with through this segment. That is a substantial amount of weight to lose, but you’ll be too busy being dead or dying to really appreciate the weight loss. To replicate this kind of rapid loss would take running in extremely hot weather for about a 12-hour period, without rehydrating, of course.
Now that we’ve gotten all of that grisly business out of the way, let’s finish up with some commonly asked questions from around the web. Take a look at five of these questions below, answered for your convenience.
There are a few ways you can test yourself for signs of dehydration before you suffer from any of the symptoms outlined in the article above. You may have heard of the simplest ones before, take a look.
The first is where you pinch the skin of your arm and watch how long it takes for that skin to return to its natural position, often called a skin elasticity test. If the skin springs back within three seconds, you’re in the clear. If it’s any longer than that, get some water.
The next is similar where you hold a hand up so that it’s above your heart, press the nail bed till it turns white, release, and see how many seconds it takes to turn pink. If it’s over two seconds, you’re dehydrated and should drink as soon as possible.
To help confirm dehydration in cases where your symptoms are more severe, you should see a medical professional who can give you a blood test or a urinalysis to determine whether you’re hydrated and to what degree.
There are three distinct interconnected types of dehydration, but they’re quite easy to distinguish.
The first and second dehydration types are hypotonic and hypertonic, which are opposite to one another in what they mean. Hypotonic dehydration is where you have a loss of electrolytes or salts, and hypertonic is where you have a loss of water. Some people have different sweat types, so it’s possible to lose the water or salt content of your body separate from one another, producing a different kind of dehydration.
The most common in humans is the third, isotonic, which is simply the absence of both water and salts in your system to an equal degree.
If you need to hydrate in a short amount of time, you have a few options. Five, to be exact. The first is one that we probably don’t need to tell you, but it’s a fact that drinkable water is the best, and often cheapest, way to rehydrate. It has no sugar or calories added to it, so you can fill up your hydration pack and not need anything else.
As outlined above, some people lose more or less salt through their sweat than others. If the former applies to you, you need to also replace the extra salt that you’ve lost.
You can also drink coffee and tea in moderate amounts. We need to stress moderate amounts as caffeine is a diuretic, making you lose even more hydration. However, when drank sparingly, it can be just as effective as water for a shorter-term, energizing alternative. We’re talking doses of caffeine below 250 to 300 milligrams, so two to three 240 milliliter cups of coffee or five to eight cups of tea at the same volume.
If your dehydration is caused by specific symptoms that drain the water in your body, which are the fun ones like diarrhea and vomiting, then there are oral hydration solutions available for you. These water-based solutions are packed with sodium, chloride, and potassium to replace lost electrolytes, too, and have dextrose sugar in them. Depending on which ones you get, you can also get other nutrients like prebiotics and zinc. These are one of the more expensive options if you buy them commercially, but you can also find some home recipes online.
If you’re dehydrated but have access to more food than water, then it’s wise to know which foods are best for getting you out of dehydration. Only a fifth of our overall hydration comes from solid foods, so you can’t rely on food alone to maintain healthy levels of hydration. When it comes to hydrating foods, however, some foods are better than others.
One of the best things to eat to replenish your hydration is watermelon. It’s kind of in the name, and this fruit is known for being 92% water, with the rest being sugar and other minerals that are also beneficial for hydration. This means that it’s low in fiber, too.
You can also add more cucumber to your diet since they’re 96% water. Eating any amount of cucumber will deliver twice the hydration level as the same volume of water, so it’s quite an efficient vegetable to eat if you need fast rehydration.
Bananas are a great option, too, since they’re 74% water and packed with potassium. Potassium is one of those electrolytes that are important for balanced hydration. Strawberries have 92% and can be served with cream too, without impacting their hydrating properties. On the less sweet side, tomatoes, spinach, radishes, and iceberg lettuce are also great for more savory hydrating options.
If you haven’t noticed, these are all fruits and vegetables (with a focus on berries) that contain a lot of water and some of those electrolytes that are best for hydration.
There isn’t much that hydrates better than water for consistent hydration, but you do have an alternative. That alternative is milk since it provides hydration whilst delivering many different nutrient types into your body. The electrolytes in milk help balance the water content in your system, so it’s one of the only liquid alternatives to water that can be used for longer-term hydration.
But which milk is best? There are different kinds of milk and they’re certainly not made equal. Thankfully, this has been researched before, and it was found that skimmed and low-fat milk have the same, or similar, rehydration properties as sports drinks. That means it’s a great after-workout drink to replenish lost nutrients through sweating. Full fat milk is the worst option, especially if you’re drinking it to combat water-losing symptoms like diarrhea or vomiting.
Milk also has a lot of protein, so drinking it after exercise will help muscle repair. Even if you’re not lactose intolerant, milk can be bloating at the best of times, however, so drinking it after exercise can cause some discomfort. We’d advise you to drink it when you know the rest of your day is relaxed.
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