How Long Does It Take To Rehydrate? Tips to Stay Safe

“Hydrate, hydrate, hydrate.” It’s common advice that every runner has heard time and time again. After all, not only do runners need to keep up with our body’s daily hydration needs, but we also need to compensate for dehydration caused by exercising by making up for any fluids lost in sweat.

But, once we set the basics aside, what does hydration actually look like for a runner? How long does it take to rehydrate your body after running? If you are dehydrated, how long does it take to rehydrate after a workout?

In this guide, we will examine rehydrating after running to help you optimize your hydration strategy.

We will cover: 

  • The Importance of Hydration
  • Consequences of Failing to Rehydrate After Exercise
  • Factors that Affect How Much You Need to Drink to Rehydrate After Working Out
  • How Much Do You Need to Drink to Rehydrate After Working Out?
  • What Should I Drink to Rehydrate After Working Out?
  • How Long Does It Take to Rehydrate After Exercising?
  • How Long Does It Take to Rehydrate from Mild Dehydration?
  • How Long Does It Take to Rehydrate from Moderate Dehydration?
  • How Long Does It Take to Rehydrate from Severe Dehydration?

Let’s get started!

How long does it take to rehydrate? A woman pouring water into a glass.

The Importance of Hydration

We all know drinking water is vital to our health. According to the US Geological Survey, up to 60% of the adult human body is water. The brain is roughly 73% water, the lungs are about 83% water, and the muscles and kidneys are both approximately 79%. 

Even physiological structures we envision as being very dry contain appreciable amounts of water. For example, the bones are about 31% water. 

Therefore, it’s no surprise we need to stay properly hydrated. 

Consequences of Failing to Rehydrate After Exercise

Before we answer the question, how long does it take to rehydrate after running, let’s consider the consequences if you don’t rehydrate properly after a workout.

If you don’t replace the fluids lost in sweat and expired gasses from your run with adequate rehydration, you’ll move into a state of dehydration, which can result in the following:

  • Poor temperature regulation: The body’s thermoregulatory control mechanisms do not operate well when you are not properly hydrated, so you might be uncomfortably hot or cold.
  • Increased heart rate: A state of hypohydration (low body water levels) increases your heart rate.
  • Dizziness and low blood pressure
A woman lying on the ground dehydrated.
  • Reduced strength 
  • Slowed dehydration: Gastric emptying rate slows and peristalsis can slow down as well, leading to digestive distress and constipation.
  • Poor motor control 
  • Compromised decision making, focus, and mental clarity
  • Poor recovery from your workout
  • Increased muscle soreness post-workout: Rehydrating after exercising can encourage circulation to fatigued muscles, helping deliver reparative oxygen and nutrients and flushing out metabolic byproducts from exercising. This can potentially reduce the severity of delayed-onset muscle soreness (DOMS).
  • Compromised athletic performance: If you don’t rehydrate enough after your run, you’ll start your next workout dehydrated. Dehydration of just 2% of your body mass can reduce your performance and increase the likelihood of muscle cramps while running.

For example, if you weigh 150 pounds, losing 3 pounds through sweat is enough to negatively impact your physical performance.

A man walking in te woods, holding his head.

Factors that Affect How Much You Need to Drink to Rehydrate After Working Out

There’s no one-size-fits-all approach to how much water you need to drink in a day or how much fluid you should consume after exercising. 

The amount of water you need to drink after working out to be properly hydrated depends on numerous factors, such as the following:

  • Climate and environmental conditions
  • Workout intensity
  • Workout duration 
  • Clothing
  • Your personal sweat rate (heavy sweater, light sweater, etc.)
  • Body size
  • Your fitness level
  • Medications you take 
  • Hydration status before your workout 
  • Overall health status and disease states (for example, if you have heart disease, diabetes, cystic fibrosis, etc., you need to drink more fluids)
  • Your diet (salty foods vs. vegetables, fruits, and water-containing foods)
  • Caffeine and alcohol consumption 
A man drinking water.

How Much Should I Drink to Rehydrate After Exercising?

Though the sheer number of factors that can affect how much you should drink after working out is evidence enough that rehydration amounts are highly individualized, the general recommendation is that runners should aim to drink 1.5 times the fluid you lost while exercising. 

For example, the National Athletic Trainers’ Association recommends rehydration should involve replacing up to 150% of the estimated fluid lost in no more than four hours after your workout, noting that rapid rehydration after exercise restores hydration status, improves recovery, reduces symptoms of dehydration, and decreases post-exercise fatigue.

Overshooting with this 1.5 times the weight of fluids lost is designed to build in a buffer to compensate for additional fluids you’ll continue to lose through residual sweating and urination even after the actual exercise has stopped.

As an example, if you lost 3 pounds (48 ounces) of water weight from sweating from the start of your run to the time you’re home, you’ll want to try and drink 4.5 pounds (72 ounces) of water. 

Technically speaking, a pound of water is slightly less than 16 ounces (15.34 US fluid ounces), but the 16 ounces to a pound is an easier conversion for this already estimated guideline.

It is important to note that this rehydration amount does not need to be consumed all at once as soon as your workout is over. Rather, it’s actually most effective to spread out your rehydration fluids over the next 2-4 hours or so to aid absorption and prevent diluting your electrolytes too rapidly.

A woman drinking water after a workout at sunset.

What Should I Drink to Rehydrate After Working Out?

The National Athletic Trainers’ Association Position Statement asserts that plain water should be fine before, during, and after workouts lasting an hour or less, provided you have a well-balanced diet, an average sweat rate, and didn’t have an extremely intense workout.

In these cases, and for workouts lasting more than an hour, fluids containing electrolytes and carbohydrates can be beneficial.

How Long Does It Take to Rehydrate After Exercising?

Now we get down to the ever-important question of how long does it take to rehydrate after exercising. 

Unsurprisingly, there’s no easy answer to this one either, as rehydrating times depend on many of the same aforementioned factors that affect how much you need to drink after working out, as well as what fluids you choose to rehydrate with (water, electrolyte beverages, sports drinks with glucose, etc.) and whether you’re also eating or consuming food alongside the fluids.

If your stomach is empty, rehydrating will be faster because your stomach can digest water faster if it’s not also working to digest any food. Digesting water through an empty stomach can take as little as 15 minutes, depending on how much water you drink.

On the other hand, if you are eating food along with the fluids you are drinking, rehydration takes longer because your body prioritizes digesting food over water. It can take up to two hours to rehydrate when food and water are consumed in tandem.  

A man drinking a bottle of water.

How Long Does It Take to Rehydrate from Mild Dehydration?

According to a study from the Journal of Strength and Conditioning Research, rehydration from a state of mild dehydration can be achieved with 20.3 oz (600ml) of water or an electrolyte beverage in 45 minutes.

In most cases, your body is mildly dehydrated after a standard workout or run. Therefore, generally speaking, rehydration after exercise may take about 45 minutes, so long as you don’t sweat profusely, start the workout already dehydrated, or fail to drink 4-6 ounces of fluid every 15-20 minutes or so while exercising. 

If you do sweat a lot or did not drink during your workout, you are likely more moderately or severely dehydrated and rehydration after your workout will take longer.

How Long Does It Take to Rehydrate from Moderate Dehydration?

The more dehydrated you are, the longer it will take to rehydrate, and the more important it will be to have electrolyte-containing solutions like oral rehydration fluids. 

While our natural instinct may be to drink as much as we can as fast as possible, this can actually be counterproductive and even dangerous, as rapid fluid overload can induce shock.

For moderate dehydration, for example from Cholera, the CDC recommends adults drink 1 liter of oral rehydration fluids per hour. 

Two people leaning on a bridge drinking water.

How Long Does It Take to Rehydrate from Severe Dehydration?

Severe dehydration usually requires IV fluid replacement and often takes 24 hours or more.

Hopefully, we never get to the point of severe dehydration by taking the proper precautions and staying well-hydrated throughout the day and before and after our workouts. Make the effort to consume the appropriate amount of fluids to avoid dehydration at all costs.

Now that we’ve answered the question, how long does it take to rehydrate, let’s brush up on our electrolytes in the following guide: Fluid and Electrolytes: A Complete Runner’s Guide.

In addition, if you are looking to improve your nutrition, on the whole, take a look at the following articles on runner’s nutrition:

Ultramarathon Nutrition Guide: What To Eat Before, During, After An Ultra

The Complete Runner’s Diet: What To Eat For Top Performance

The Best Popular Diets For Runners: 3 Healthy Choices

10 Rules Of Nutrition For Runners

Running Nutrition Guide: What To Eat, For Runners

A bucket of sports drinks.

Amber Sayer

Amber Sayer

Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, and contributes to several fitness, health, and running websites and publications. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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