Dehydration: Signs, Symptoms, & Treatment

By John Bernard, MD
Medically reviewed checkmarkMedically reviewed
May 1, 2020

Did you know that you can become dehydrated without necessarily feeling thirsty? If you’re experiencing low energy, headaches, or lightheadedness without an apparent cause, your body may be dehydrated.

Because our bodies use water for so many regular functions, dehydration can take many forms and cause varying side effects. Adequate hydration is necessary for healthy skin, muscles, brain, organ function, and much more. The good news is that it’s fairly easy to stay hydrated—all it takes is a regular daily habit of drinking water and knowing when to increase your fluid intake to account for exercise, heat, or illness.

It’s important to be familiar with various dehydration symptoms in adults and children, because they can be misinterpreted as other causes. If the signs of dehydration go unaddressed, it can progress into a serious issue that requires emergency treatment. If you know what to look for, you can generally nip the problem in the bud. Do you know how to tell if you are dehydrated?

What Is Dehydration?

Roughly 60% of the human body is made up of water. We need water in our cells, blood vessels, and in between our cells in order to survive and function normally. We also need electrolytes, which are minerals that help to balance the amount of water in the body, as well as the body’s pH level, nutrients, and waste.

According to the National Academies of Sciences, the recommended fluid intake from all sources—foods as well as liquids—per day for women is 2.7 liters while for men the number is 3.7 liters. Many foods, including many fruits and vegetables, have a high percentage of water content.

Because we lose fluids gradually throughout the day—through breathing, sweating, urinating and defecating—we have to eat and drink regularly to replenish water and electrolytes. Our sense of thirst generally tells us when our body is in need of more water, and we also get water and electrolytes (such as sodium, calcium, magnesium, and potassium) from the food we eat.

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Dehydration refers to a state where the body has lost more water than it has gained, and therefore normal functions such as circulation, respiration, and organ functions cannot work properly. If you don’t have access to water, forget to drink, or your sense of thirst is impaired, you may lose more water than your take in, leaving your body dehydrated.

Although mild dehydration can cause uncomfortable symptoms and abnormal bodily functions, if treated promptly with adequate fluids, it will not cause serious harm.

If left untreated, mild dehydration will become severe dehydration, defined as a loss of 12% or more of bodily fluids. Severe dehydration is a serious medical issue that can significantly impact bodily functions and organs and may require hospitalization.

What Are the Symptoms of Dehydration?

Fortunately, our bodies usually give us plenty of warning signs that we are dehydrated before it reaches a serious enough level to require hospitalization. One of the most obvious signs is a sense of thirst, which is our body’s natural way of telling us it needs more fluids. However, it is possible to become dehydrated without feeling thirsty, so it’s essential to be able to recognize the other common side effects of dehydration.

The signs of dehydration typically begin with a feeling of thirst, fatigue, and an unusually dry mouth. Other signs include:

  • Urine color and production: If the color of your urine is pale yellow or clear, this is a sign that your body is well hydrated. If your urine appears as a dark golden or deep amber color, this indicates dehydration. As your body becomes dehydrated, you may also notice the urge to urinate is less frequent.
  • Dry skin: Because you lose moisture through your skin, you may notice your skin appearing shriveled, dry, rough, flaky, cracked, or tight when dehydrated.
  • Low blood pressure: This is another common side effect of dehydration, which can also present itself through cold and clammy skin or dizziness.

As dehydration progresses, moderate dehydration symptoms include:

  • Headache
  • Muscle weakness
  • Lethargy
  • Bad breath
  • Dry or sticky mouth
  • Hunger
  • Constipation, dry stool, or stool that looks like small lumps

If the body doesn’t receive adequate fluids after this point, the symptoms above will likely worsen. When a person reaches the point of severe dehydration, additional symptoms may include:

  • Sunken eyes
  • Lack of sweating
  • Low blood pressure
  • Increased heart rate
  • Fever
  • Delirium
  • Fainting
  • Unconsciousness

In young children and babies, dehydration symptoms and side effects may present differently than in adults. For a variety of reasons, babies and young children are more likely to become dehydrated than most adults.

Signs of dehydration in kids may include:

  • The soft spot on the top of a baby’s head appears sunken
  • Dry mouth or tongue
  • Irritability
  • Unusual sleepiness or drowsiness
  • Crying without any tears appearing
  • Sunken cheeks or eyes
  • They haven’t had a wet diaper in over three hours

What Causes Dehydration?

Dehydration occurs when the body loses too many fluids or doesn’t take in enough fluids, causing a deficiency of water and electrolytes.

Dehydration causes can range from illnesses that lead to expelling fluids rapidly (such as diarrhea or vomiting), to more subtle influences such as failing to replenish the water our body gradually loses throughout the day.

Common dehydration causes include:

  • Failing to drink enough water: If you drink too little water or you don’t drink water frequently enough throughout the day, you can gradually dehydrate your body.
  • Extreme heat or humidity: Too much time outside on a hot day, or in a humid place like a sauna, can leave you dehydrated since your body loses water through sweat.
  • Vigorous physical activity without water: Strenuous physical activity can cause you to lose water through sweating. If you don’t replenish your fluids by drinking water during or immediately following intense exercise, you can quickly become dehydrated.
  • Diarrhea: This is the most common cause of dehydration. Normally, the large intestine absorbs water from the food you eat. However, when you experience diarrhea, the large intestine isn’t able to absorb water. Prolonged diarrhea can cause rapid dehydration and may even lead to hospitalization.
  • Vomiting: A stomach flu, food poisoning, or any illness that causes frequent vomiting can dehydrate your body quickly. It is also challenging to replace your fluids if you aren’t able to keep liquids down. This is why it’s important to continue attempting to drink water (slowly) after any bouts of vomiting.
  • Fever: A high fever often causes your body to sweat, which can lead to a significant loss of water. If the fever is paired with diarrhea or vomiting, the fluid loss may be even larger.
  • Diabetes: If you have diabetes, high blood sugar can lead to more frequent urination, causing you to lose more water than usual.
  • Medications: Some medications are diuretics, meaning that they increase urination, forcing your body to lose more fluids than usual. Diuretics may be helpful for some illnesses or conditions, as long as you remember to increase water intake to make up for the loss. There are other medications, including some antihistamines, blood pressure medications, and antipsychotics that can also cause increased urination as a side effect.
  • Alcohol and caffeinated beverages: Alcohol and caffeine both act as diuretics. Drinking an excess of beer, wine, liquor, coffee, tea, or other caffeinated beverages can lead to very frequent urination in a short amount of time. These substances don’t help your body replenish its water resources, so if you don’t drink enough water along with them, you will become dehydrated.
  • Burns: Dehydration is a common risk for people who have suffered third degree burns, as this type of injury can impact your body’s water storage. Severe burns may damage the blood vessels, allowing fluid to leak into the surrounding tissue. If your blood vessels lose too much fluid in this way, the body becomes dehydrated.

Risk Factors and Complications

While dehydration can impact people of all ages and lifestyles, there are factors that put some people more at risk. Those at higher risk of becoming dehydrated should be vigilant about drinking plenty of water throughout the day. Risk factors for becoming dehydrated include your age, activity level, and environment.

Infants and young children are at a higher risk of dehydration due to diarrhea and vomiting; diarrhea is very common in young children and their bodies can become dehydrated more quickly than adults. Because infants aren’t able to tell us outright when they feel thirsty, they rely on their caregivers to be attuned to their needs and the symptoms of dehydration.

On the other end of the spectrum, seniors are also at higher risk of dehydration, as the sense of thirst can diminish as we get older. With a decreased sense of thirst, it’s easier for seniors to forget to drink enough water throughout the day. To add to this, early signs of dehydration—such as fatigue, dizziness, or dry mouth—may go unnoticed at first because they can be side effects of other conditions or of natural aging.

Aside from age, the amount of activity you engage in and the climate you live in can also impact the amount of fluid loss your body undergoes each day. You may be at higher risk of dehydration if:

  • You are an athlete
  • You live in a high altitude
  • You have a chronic illness such as diabetes, kidney disease, alcoholism, or an adrenal gland disorder

If dehydration is left untreated, it will become more severe. And because the body relies on water for so many normal functions, severe dehydration can cause life-threatening issues. It is important to stay alert for the early signs of dehydration in order to treat it before it worsens—because even though dehydration isn’t usually difficult to alleviate, it can become very harmful and even life-threatening if left unresolved.

Severe dehydration may cause complications such as:

  • Low blood volume
  • Seizures (due to imbalance of electrolytes)
  • Kidney stones
  • Urinary tract infection
  • Kidney failure
  • Heat exhaustion
  • Heat stroke

Diagnosing Dehydration

Your doctor will likely be able to tell whether you’re dehydrated or not based on your physical symptoms. First your doctor will check your blood pressure, since low blood pressure is a typical sign of dehydration. They will also check your heart rate. If it’s faster than normal, this may indicate that you’re dehydrated.

If your doctor believes you are severely dehydrated, they may order a blood test and a urinalysis. A blood test is used to check whether you have appropriate levels of electrolytes, like sodium and potassium, and to assess your kidney function. If dehydration is serious enough, it can impact the kidneys and cause certain changes in your electrolytes. A urinalysis will help reveal the degree of severity of your dehydration.

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Dehydration Treatment

The only way to treat and cure dehydration is to replace the fluids and electrolytes the body has lost. The right method for delivering fluids—whether with at-home remedies, over-the-counter solutions, or hospitalization—will depend on your age and how serious the level of dehydration is.

Treating severe dehydration

Severe dehydration should be treated in a hospital. Health care professionals will use an intravenous line to deliver water along with important electrolytes, such as salts, directly into your body through a vein, since this is the fastest way to cure dehydration.

Treating moderate dehydration in adults and older children

Adults and older children who are suffering from mild dehydration can generally treat the issue at home by drinking water or a sports drink that contains electrolytes. For children, it’s recommended to dilute sports drinks with water, as most sports drinks contain a large amount of sugar which can make diarrhea worse.

You can also alleviate dehydration by eating foods with high water content, such as:

  • Melons, including watermelon and cantaloupe
  • Celery
  • Lettuce and spinach
  • Cucumbers
  • Cauliflower

If you are dehydrated, refrain from drinking alcohol, coffee, or other beverages that act as diuretics as these can cause your body to lose even more water.

If you are experiencing active diarrhea, avoid drinking fruit juices and soft drinks such as colas or other sodas, as these can make diarrhea worse.

Treating dehydration in infants and toddlers

If your infant or young child has experienced diarrhea, vomiting, or fever causing dehydration, you can treat it with an over-the-counter rehydration solution, such as Pedialyte or a similar brand. If you’re not sure which to choose, ask your pediatrician if they suggest a particular brand. These solutions are made up of specific ratios of water, sugars, and salts that help the body take in fluids and are taken orally. It’s recommended to start by giving your child 1-2 teaspoons of the solution every five minutes, and then gradually increase the amount as your child is willing to drink more.

If your baby refuses to drink or has trouble swallowing the solution, you may opt to use a syringe to push the liquid down the throat.

Dehydration Prevention

Preventing dehydration comes down to consuming enough fluids—through beverages and foods with high water content—to keep up with the fluids your body loses in a given day.

On a typical day, you should drink roughly two liters (eight 8-ounce glasses) of water to keep up with the normal rate of fluid loss and prevent dehydration. You may need to drink more on an especially hot or humid day, as your body will lose more water through sweat. If you struggle to remember to drink water (this is particularly common in elderly populations), try different strategies to help encourage you to get your daily water, such as:

  • Keeping a reusable water bottle with you at all times
  • Setting an alarm each hour to remind you to have a glass of water
  • Pairing a full glass of water with each meal, or with a medication you take daily
  • Adding some flavoring to your water to make it more enticing
  • Eating foods that are high in water content with every meal

If you engage in vigorous exercise, spend time in a sauna, drink alcohol, or do a similar dehydrating activity, increase your water intake to make up for the additional fluid loss. Refrain from highly strenuous activities in extreme heat.

If you are currently sick with symptoms including fever, diarrhea, or vomiting, be sure to drink fluids as often as your body can manage to prevent or decrease the severity of dehydration.

In general, avoid overconsumption of beverages that can cause or worsen dehydration, such as:

  • Sodas, including colas
  • Alcohol
  • Energy drinks
  • Coffee, tea, and other caffeinated beverages

When to See a Doctor

If you are experiencing mild dehydration, you can likely treat it from home by drinking water and other hydrating beverages, without a visit to the doctor’s office. You should see your symptoms ease and resolve within a few hours.

If your dehydration symptoms do not resolve after a day, or worsen, it’s a good idea to make an appointment with your doctor. You should also call your doctor if you experience frequent vomiting for more than 24 hours or active diarrhea for more than 48 hours.

For young children and babies that show signs of dehydration, talk to your pediatrician to determine the best treatment. If your child has diarrhea lasting more than 24 hours, even if there are no signs of dehydration, make an appointment with your pediatrician.

Call an ambulance or go directly to the emergency room if your symptoms are accompanied by any of the following, as these can indicate severe dehydration or kidney complications and require immediate medical attention:

How K Health Can Help

If left untreated, dehydration can lead to severe consequences.

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K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

John Bernard, MD

Dr. Bernard is an emergency medicine physician. He graduated from Jefferson Medical College in Philadelphia, and did his residency in emergency medicine at the University at Buffalo.

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