Acute vs. Chronic Dehydration In Athletes: Causes, Symptoms, Prevention, and Treatment

Dehydration doesn’t discriminate. It can happen to elite athletes, weekend warriors, and the general inactive population alike. Symptoms can be mild to severe, and in some cases fatal.

Most people associate dehydration with being thirsty. While this is one sign that your body may be starting to 'dry out' like a grape in the sun, there are other things to be aware of that may help you stave off dehydration.

What’s more, dehydration can be classified as either acute or chronic. In this article, we will discuss the differences between the two, what to look out for, how to prevent dehydration, and how to treat it if it happens to you.

What is Dehydration?

According to the American College of Sports Medicine (ACSM), dehydration simply refers to the loss of body water. However, it is a lot more complicated than that. We need to narrow our focus on exercise-induced dehydration. We’re athletes after all.

Exercise-induced dehydration refers to:

  1. A two percent or more bodyweight loss from entering an exercise with an existing water deficit
  2. Not drinking enough fluid during exercise to combat this loss of water

How does dehydration affect athletes?

When athletes lose two percent or more bodyweight via sweating, bad things can happen. These include:

  • Impaired performance
  • Increased heart rate
  • Reduced blood flow
  • Increased lactate production
  • Electrolyte imbalances
  • Increased skin temperature
  • Heat exhaustion
  • Heatstroke
  • Rhabdomyolysis (release of damaging protein resulting from muscle damage)
  • Death

Did that last bullet point catch your attention? I hope so because dehydration is a high stakes poker game with some serious consequences if you roll the dice wrong.

Now it’s time to get down to brass tacks and discuss the different types of dehydration. Acute and chronic

Acute Dehydration

Acute dehydration, as the name implies, happens in the short term and occurs when you lose more fluid than you take in. It can be summed up like this:

Fluid out > Fluid in

Acute dehydration affects the way the body functions and can inhibit athletic performance. The good news is acute dehydration is easy to spot and highly preventable

Causes of Acute Dehydration

  • Not drinking enough fluid throughout the day or during exercise.
  • Living in a hot and humid environment.
  • Not being heat acclimated
  • Taking diuretics
  • High sweat rate

Signs & Symptoms of Acute Dehydration

  • Increased thirst.
  • Dry mouth and tongue.
  • Headache
  • Dizziness
  • Rapid heartbeat and breathing.
  • Dry, cool skin.
  • Not peeing very much or darker colored urine.
  • Muscle cramps

Testing for Acute Dehydration

The tests for acute hydration are simple and straightforward and do not require any invasive techniques. These are:

  1. Check the color of your urine. If it is not clear or pale yellow you are most likely mildly dehydrated.
  2. Measure urine specific gravity. A urine specific gravity test compares the density of urine with the density of water in your bladder. From the results, you can determine hydration status. You’ll need a medical professional to do this for you or buy a refractometer and know how to interpret the results.

Treatment for Acute Dehydration

Treating acute dehydration is fairly simple.

  • Replenish fluids. This can involve drinking water, electrolytes, and sports drinks. Avoid coffee, teas, and sodas as they may have a diuretic effect and increase urine output.
  • Cool off. Find a shady spot or head inside to lower your body temperature. This will decrease your sweat rate and the loss of additional fluids.

How long does it take to recover from acute dehydration?

Generally speaking, acute dehydration can be resolved in 30-60 minutes once fluid is consumed in adequate amounts and absorbed by the body.

Chronic Dehydration

Unlike short-term, acute dehydration, chronic dehydration occurs when dehydration recurs over longer periods of time. For example, not drinking enough water on a daily basis (over the course of a month) to replace fluids lost through bodily functions, activities of daily living, and exercise.

If left untreated, chronic dehydration can have disastrous consequences and will require immediate medical attention.

Causes of Chronic Dehydration

The causes of chronic dehydration are similar to those of acute dehydration. Also included are:

  • Living in a warmer or humid climate, or both.
  • Spending a lot of time exercising/working outdoors.
  • Not having access to adequate water
  • Frequent diarrhea or GI distress
  • Women who are pregnant and breastfeeding are at higher risk for chronic dehydration.

Signs & Symptoms of Chronic Dehydration

  • Intense thirst all the time. No explanation needed here. Your body is smart and wants to survive. It’s saying, “Hey big dummy, take a drink!”
  • Dizziness and confusion. Multiple studies have demonstrated that chronic dehydration makes mental tasks more difficult and impairs working memory.
  • Dark-colored urine. In a hydrated state, urine should be clear to pale yellow. The darker it gets the more dehydrated you are.
  • Extreme muscle fatigue. Fun fact! Muscles are 75% water. H2O plays an important part in muscle repair and recovery. Without enough of it, muscle protein synthesis is inhibited.
  • Very dry, flaky skin. 60% of the human body is water. It follows that being chronically dehydrated is going to make your skin feel dry and leathery.
  • Constant headaches. Excess metabolic waste and a drop in blood and oxygen flow caused by chronic dehydration can trigger pain signals in the brain which in turn cause headaches.
  • High blood pressure.
  • Kidney stones.
  • Digestive problems. Your body needs adequate water to digest and absorb food. Without enough, you may experience constipation and acid reflux.
  • Sunken eyes

Testing for Chronic Dehydration

There are two ways to test for chronic dehydration:

  1. A urinalysis. Basically, a doctor will test your urine to see if your body is producing enough or too little.
  2. Blood panel testing. This test will look at the levels of electrolytes (i.e. sodium and potassium) in your body and also examine if your kidneys are functioning properly to process urine efficiently.

Treatment for Chronic Dehydration

Unfortunately, just “drinking enough water” is not a cure for chronic dehydration. More than likely you will need to drink electrolyte beverages to restore fluid balance and help your body hold on to more of the fluids you are drinking.

Additionally, you may be put on a drinking schedule where fluid is measured out and consumed throughout the days at certain points.

In the most extreme cases, an IV may be needed to directly deliver fluid into your bloodstream.

Last but not least you may need to cut back on habits that caused the extreme fluid loss. This includes decreasing alcohol and caffeine consumption and cutting back on any diuretic medications you may be on.

How long does it take to recover from chronic dehydration?

The time it takes to recover really depends on why it happened in the first place and how long you have been chronically dehydrated. Simply put, there is not an exact number of days and will depend on an individual's circumstances.

Your doctor may perform the tests listed above over the course of 60 days to determine when you are back in a euhydrated (normal body water content) state.

How to Prevent Acute and Chronic Dehydration

The following guidelines suggested by the International Society Of Sports Nutrition should leave athletes in a hydrated state throughout the day and during exercise.

General Hydration Guidelines

  • Drink 13 - 20 ounces of fluid (one average-sized water bottle) every two to three hours.

Staying Hydrated Before Exercise

  • Drink 16 - 20 ounces of fluid (water or sports drink) 2-3 hours before exercise and 6 - 10 ounces of fluid 10 to 20 minutes before exercise. This ensures optimal hydration.

Staying Hydrated During Exercise

Rehydrating After Exercise

  • Drink 50 ounces of fluid (about 3 average-sized water bottles) for 1 kilogram (2.2lbs) of weight lost during exercise.

The Best Way to Stay Hydrated

There are a lot of opinions on the best way to hydrate during exercise to prevent dehydration.

However, the two most common and research-backed methods of staying hydrated are drinking on a schedule and drinking to thirst.

We’ll briefly cover them here. For a more detailed explanation on each go here (drinking on a schedule) and here (drinking to thirst).

Drinking on a Schedule

Drinking on a schedule is exactly what it sounds like. An athlete consumes fluid at specific points during racing or training.

For example, taking sips of sports drink every 10-15 minutes that usually equates to 16-32 ounces of fluid per hour.

While this method is tried and true, some athletes experience GI distress from drinking too much and other times it is not practical to drink on a schedule (i.e. during a mountain bike race on rocky singletrack.

Drink to Thirst

Again, this is exactly what it sounds like. It can be summed up by:

Drink when you are thirsty and don’t when you are not.

The research has demonstrated that this method is just as effective as drinking on a schedule when it comes to preventing dehydration or the 2% body weight loss from sweating.

Do you really need to replace all the fluid you lose from sweating?

The short answer to this is no. Besides, it is very difficult to replace every drop of fluid you lose through sweat during exercise. And that’s OK!

Even if you drink on a schedule or drink to thirst, more than likely you will still lose body weight through sweat. This shouldn’t have a negative impact on performance if you are following the hydration strategies outlined above.

What factors contribute to dehydration?

There are a lot of variables that can determine how quickly an athlete can become dehydrated. These are discussed below.

  • Physical activity. More specifically the duration and intensity of the activity. Obviously, athletes (i.e. sprinter) whose workouts are short won’t sweat as much compared to say, a marathon runner, whose workout may go beyond two hours. Also, more intense exercise will cause greater sweating compared to low-intensity exercise.
  • Individual variability. Factors here include body weight, genetic predisposition, how acclimated an athlete is to the heat, and metabolic efficiency.
  • This is a biggie. Hot and humid environments will dehydrate an athlete faster than a cold, dry, temperate environment.
  • Clothing/equipment worn. Wear light, loose-fitting garments that are breathable and moisture-wicking.
  • Sweat rate. Some people sweat more than others. This will lead to greater fluid and electrolyte loss. Calculating your sweat rate is important as it can help you determine how much fluid you should be consuming every hour during exercise to prevent dehydration.

How to Determine Your Fluid Requirements/Needs

Use the following formula to get an idea of your hourly sweat rate:

16 x [(your starting weight in-lbs) – (weight in-lbs after 1-hour of exercise)] + [fluids consumed during exercise in oz] = sweat loss in oz/hour.

Say for example I weigh 161 pounds before exercise and 160 pounds when I finish my workout. The calculation would look like this:

16 x [(161 lbs) – (160)] + [8] = sweat loss in ounces per hour.

16 x 1 = 16

16 + 8 = sweat loss of 24 ounces per hour

Therefore, I would try to drink 24 ounces of fluid an hour to offset the fluid I am losing through sweat.

Preventing Dehydration During Hot Weather Exercise

  • Exercise early in the morning or late at night when the temperature is cooler.
  • Avoid the midday sun when it is the most intense.
  • Wear a hat and light-colored clothing to reflect the sun’s heat.
  • Consider exercising inside when it is not feasible to exercise in the morning or at night.

How long does it take to die of dehydration?

What a morbid question. The norm is 10 days after absolutely no fluid is consumed.

What are Hyperhydration and Hyponatremia?

More of something isn’t always better and this can be the case when an athlete drinks WAY TOO MUCH fluid before and during exercise. Especially if it is water, as this can cause hyponatremia.

Hyponatremia happens when an individual drinks too much water which throws the body’s electrolyte balance out of whack. Mild hyponatremia can lead to headaches, nausea, confusion, and fatigue while severe hyponatremia can cause comas, seizures, and death.

To avoid hyponatremia athletes should NEVER over hydrate while also consuming salty (i.e. electrolytes) foods and beverages during exercise.

Supplements that May Help with Dehydration

So far we have discussed several conventional methods to prevent dehydration. While proper hydration and nutrition will always be your best bet to battle dehydration, there are a few supplements that may also help.


Most people think electrolytes prevent cramping. While this may be the case in rare circumstances, electrolytes play a bigger role when it comes to dehydration because they can:

  • Help keep more water in your body
  • Maintain blood volume
  • Prevent hyponatremia


Creatine isn’t just for the gym bros to get big and strong. It can help with hydration! When creatine is taken it promotes water uptake in the muscles. Properly hydrated muscles = happy muscles that perform well! 2-3 grams daily is the dose here.


Betaine helps with water retention in the cell (osmolyte) and thus protects the cell from hydration. 2.5 up to 6 grams daily.


Glycerol acts like creatine in that it helps the cells to uptake more water. 1.2 grams per kilogram body weight and 26 milliliters per kilogram bodyweight of fluid, 60 minutes prior to exercise.

The Bottom Line About Dehydration

Both acute and chronic dehydration can derail your athletic performance AND have a negative impact on your health.

By following the advice given above, an athlete will remain in a euhydrated (adequately hydrated) state throughout the day and before, during, and after exercise.

About The Author Matt Mosman - Spearfish, South Dakota

Matt Mosman (MS, CISSN, CSCS) is a research scientist, endurance athlete, and the founder and Chief Endurance Officer at EndurElite. Matt holds his B.S. in Exercise Science from Creighton University and his M.S. in Exercise Physiology from the University of California. Matt and his family reside in Spearfish South Dakota where they enjoy running, mountain biking, camping, and all the outdoor adventures Spearfish has to offer.


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