How to rehydrate fast: What the science says

Written by Robb Wolf (opens in a new tab)

Medically reviewed by Ecler Ercole Jaqua, MD, MBA, DABOM (opens in a new tab) and Jared Meacham PhD., RD, CSCS (opens in a new tab)

Dehydration means your body has lost fluid in an amount that affects its functioning. People typically lose electrolytes with fluid loss, as well. Rehydrating fast involves consuming enough fluid and electrolytes to support fluid balance and bodily processes, such as nerve and muscle function. How long it’ll take you to get rehydrated depends on individual factors, including how much fluid you’ve lost and why.

Fun fact: Your body is made up of up to 60%Opens in a new tab water. Additional fun facts: Your lungs are made up of about 83% water, your kidneys and muscles about 79% each, your brain and heart about 73% each, your skin about 64%, and your bones about 25%.

Now you can crush at your next trivia night, but do you know how to rehydrate fast or what to drink when dehydrated?

DehydrationOpens in a new tab occurs when the body loses too much water and other fluids to perform its functions properly. As you can see by how much of your body is water, a major reduction in fluid impacts nearly every bodily system, and if dehydration happens to you, you’ll need to rehydrate fast — with fluid and electrolytes.

I’ve been there. Years back, I was trying to fuel properly for jiu-jitsu and missing the mark. I kept getting lightheaded and dizzy. Not exactly a competitive advantage. My coaches looked at what I was doing and suggested the issue was a hydration problem, specifically sodium. I wasn’t getting enough of it. When I finally started focusing on fluids and sodium, that’s when it turned around.

Restoring fluid and electrolyte balance takes longer than most people expect. What you drinkOpens in a new tab has to be absorbed from your gut, moved through your bloodstream, and delivered to muscle and other tissue. The early phase of that process — plasma volume returning to normal — can run anywhere from 30 minutes to two hoursOpens in a new tab, depending on what you're drinking; full restoration of fluid and electrolyte balance takes longer, especially if you're badly dehydrated.

But what is dehydration exactly? Is it all about water loss? How about those electrolytes? And what is the fastest way to rehydrate? In this article, we tackle these questions and more.

What Are the Signs You’re Dehydrated (and What Causes It)?

The warning signs of dehydration include dry mouth, dark or less frequent urine, fatigue, headache, dizziness, and muscle cramps.

Dehydration means you’ve lost too much fluid. When you lose water through sweat, urination, diarrhea, or any hard or hot exercise session, you also lose crucial electrolytesOpens in a new tab, which help maintain fluid balance and support bodily processes, such as nerve signaling and muscle functionOpens in a new tab.

Complicating matters is that dehydration can also cause an overconcentration in the blood of certain electrolytes. This is because when dehydration occurs, we typically lose water more rapidly than we lose electrolytes. Additionally, we can become overhydrated by drinking too much plain water, which can then dilute electrolytes in the body.

Here’s a breakdown of the terminology:

DehydratedOpens in a new tab: The body has lost too much fluid. Dehydration can be classified into three typesOpens in a new tab based on the relative loss of water and sodium: isotonic dehydration (water and sodium are lost in roughly equal proportions, often because of vomiting or diarrhea), hypertonic dehydration (water loss exceeds sodium loss, resulting in a higher concentration of sodium in the blood) and hypotonic dehydration (sodium loss exceeds water loss, resulting in a lower concentration of sodium in the blood).
OverhydratedOpens in a new tab: The body has too much water.
Electrolyte imbalanceOpens in a new tab: The body has either an overconcentration or dilution of electrolytes, including sodium, potassium, chloride, magnesium, calcium, phosphate, and bicarbonate.

Special considerations regarding hydration

Some adults and children may have different needs for staying hydrated and should consult knowledgeable healthcare providers.

Older adults are more likely to become dehydratedOpens in a new tab because they have less total body water, don't always feel thirstyOpens in a new tab when they should, and are more likely to take medications or have medical conditions that affect fluid balance. Because thirst isn't always a reliable guide, sipping no-sugar electrolyte waterOpens in a new tab throughout the day is often a better strategy than relying on thirst alone.

Kids are, by and large, just little people. Most do well eating minimally processed foods and drinking to thirst. When they're sweating buckets — think soccer tournaments, double practices, or long days in the heat — a no-sugar electrolyte can help replace what they've lost. Kelly LeVeque also recommends considering a no-sugar electrolyte when kids are sick, calling it "the perfect time to consider a no sugar electrolyte ... We wanna make sure that we're not serving high sugar sports drinks or electrolyte drinks when they're sick. Keep that sugar to a minimum." For smaller kids, it often makes sense to dilute it a bit more (around 32–40 ounces of water per packet) rather than serving it at full strength. Infants, young children with significant dehydration, or kids with certain medical conditions should follow their knowledgeable healthcare provider's recommendations.

People with kidney disease or congestive heart failure may require fluid or electrolyte restrictions and should follow their doctor’s recommendations for staying hydrated.

Common signs and symptoms of dehydration

Although symptoms vary, here are some common signsOpens in a new tab you’re experiencing dehydration:

Dry mouth or throat
Dry skin
Fatigue
Headache
Less frequent urination
Muscle crampsOpens in a new tab
Nausea
Substantial drops in physical or cognitive performance
Thirst
Weakness

If you experience rapid heartbeat (tachycardia), confusion, fainting, hallucinations, high fever, loss of consciousness, seizures, hypotension (low blood pressure), unusually dark urine, or lack of sweating even when hot, you should seek immediate medical attention.

“If patients are hypotensive and tachycardic, intravenous fluids are given relatively quickly in the ER, usually over 30 to 60 minutes,” says Paul Nystrom, MDOpens in a new tab, an emergency medicine physician who served as a Dive Medical Officer assigned to Navy SEAL teams. “If they can tolerate oral rehydration, that is also an option and in the ER that looks like water, juice, and often saltine crackers.”

Dehydration Symptoms: Signs of dehydration include dry mouth or skin, fatigue, nausea, headache, dizziness, muscle cramps or weakness, reduced urination, and decreased cognitive or physical performance.

What Is the Fastest Way to Rehydrate?

The fastest way to rehydrate when you have mild-to-moderate dehydration is consuming water along with the right electrolytes — especially sodium — instead of water alone, while severe dehydration is a medical situation that may require IV fluids.

If you are not experiencing a medical emergency, the fastest way to rehydrate at home or elsewhere is by drinking fluids containing electrolytesOpens in a new tab. Specifically, sodium, chloride, potassium, and magnesium are crucial.

Sodium helps maintain fluid balanceOpens in a new tab, supports nerve and muscle functionOpens in a new tab, aids nutrient transportOpens in a new tab across cell membranes, and regulates blood pressureOpens in a new tab.
Chloride aids with digestionOpens in a new tab, helps maintain fluid and acid-base balanceOpens in a new tab, and plays a role in nerve and muscle functionOpens in a new tab.
Potassium works alongside sodium to maintain fluid balance via a mechanism called the sodium-potassium pump (see more on this below). PotassiumOpens in a new tab also staves off muscle weakness and cramps and supports cardiovascular health.
Magnesium is crucial for proper muscle and nerve functionOpens in a new tab, neurotransmitter releaseOpens in a new tab, and helping your cells convert food into energy.

How much of each electrolyte do you need? And how do you get enough and in the right ratios? We can look to research to gauge how much electrolytes are typically lost through sweat. Sodium loss exceeds potassium. Some research suggests that you lose about 500 mg of sodiumOpens in a new tab and 120 mg of potassiumOpens in a new tab per hour, depending on activity intensity, environment, and individual variability. Salty sweaters (folks who see white streaks on their workout gear) can lose 1,000 to 2,000 mg sodium per liter per hour of sweat lossOpens in a new tab. For magnesium, the range is much larger, about 2.3 to 60 milligrams per liter of sweat lossOpens in a new tab. But if you’re engaging in intense physical activity, regardless of the weather, you will likely lose even more electrolytes than these estimates. Dietary choices can also amp up your sodium needs.

If you consume a low-carbOpens in a new tab diet or do any type of fastingOpens in a new tab, you can lose even more sodium through urineOpens in a new tab and will have higher sodium-intake needs. Diets that are mostly whole foodsOpens in a new tab also provide far less sodium than the standard American diet.

One more consideration: Our bodies have this fancy built-in sodium-potassium pumpOpens in a new tab. It’s really a protein in our cell membranes that has a crucial functionOpens in a new tab. With the help of energy created from adenosine triphosphate (ATP), the body’s universal form of energy, the pump hands over three sodium ions in exchange for two potassium ions. The difference in ion concentration creates an electrochemical gradient that allows for nerve impulse conduction. Nerve impulses from motor neurons stimulate muscle contraction. That interplay is part of why getting both sodium and potassium — not just one or the other — matters for how your body functions.

So how much of each do you actually need?

There’s no universal sodium-to-potassium replacement ratio that’s right for everyone. Your needs depend on factors like your sweat rate and sweat sodium concentration, activity level, environment, diet, and individual physiology.

But if you're already getting adequate potassium through foodOpens in a new tab (think: meat, potatoes, avocados, leafy greens, and dairy) and have higher sodium losses because of sweatingOpens in a new tab, physical activity, a high-exertion jobOpens in a new tab, or dietary patterns like low-carb eatingOpens in a new tab or fastingOpens in a new tab, your electrolyte replacement may need to skew more heavily toward sodium.

What Should You Drink When You’re Dehydrated?

An electrolyte drink or oral rehydration solution (ORS) will rehydrate you faster than drinking plain water when you’ve been sweating or when you’re sick, but plain water is fine for mild everyday thirst.

To consume fluid and electrolytes in optimal amounts, you have several options. None of these choices is “better” than another. Instead, each one has trade-offs depending on your time and resources and what your body needs. Read on for the details of each option, but this chart summarizes the key information.

Beverage	Best For	Electrolytes	Sugar	Considerations
Plain water	Everyday hydration	No	No	Alone won’t adequately restore electrolyte balance if dehydrated.
Water + LMNT	Mild-to-moderate dehydration; exercise recovery	Science-backed ratio of sodium, potassium, and magnesium	No	Helps your body hold onto more fluid than water alone; no added sugar.
Sports Drink	Sweaty exercise with carb needs	Varies by brand	Usually	Carbs may be useful for endurance ; can have as much sugar as soda and usually not a meaningful source of electrolytes.
ORS (Oral Rehydration Solution)	Mild-to-moderate dehydration from illness	Sodium, potassium	Yes	Designed for diarrhea/vomiting scenarios ; severe dehydration may require IV fluids.

Try a DIY electrolyte mix

This recipe includes a 5:1 sodium-to-potassium ratio. Mix the following ingredients.

2,500 mg sodium chloride (for 1,000 mg sodium),
385 mg potassium chloride (for 200 mg potassium)
390 mg magnesium malate OR 265 mg di-magnesium malate (for 60 mg magnesium)

Then weigh each serving. If you used magnesium malate, one serving weighs roughly 3.3 grams. If you used di-magnesium malate, one serving weighs about 3.15 grams. Add your serving to 16 to 32 ounces of water and enjoy. For flavored versions, check out LMNT’s recipesOpens in a new tab.

Try LMNT or another electrolyte drink mix

If you’re not the DIY-in-the-kitchen type, LMNT has your back. Our stick packs contain a science backed ratio of electrolytesOpens in a new tab, and they don’t contain added sugar, which I prefer to skip.

LMNT isn’t for everyone. If you have heart failure or uncontrolled hypertension, consult a knowledgeable healthcare provider(s) for personalized advice.

What about plain water or sports drinks?

The experts I interviewed have a few caveats about what not to use to rehydrate fast.

Plain water

Drinking plain water without electrolytes, especially during prolonged sweating, can leave the body short of important minerals, specifically sodium. Drinking a ton of plain water can also dilute and flush electrolytes out of your body, potentially contributing to hyponatremiaOpens in a new tab, a serious condition in which blood sodium levels drop dangerously low.

Dr. Nystrom agrees and shares an example he encountered. “I saw a relatively healthy 30-year-old female who had terrible acid reflux so had been chugging cold water for hours because that was the only thing that relieved her pain,” he says. “Her sodium levels were low, as she had overhydrated. This is an uncommon example but drinking plain water to compensate for dehydration can be dangerous.”

People who are most at risk for hyponatremia include those who:

Work outside in hot weather, especially people who are engaging in physically demanding activities, such as construction, landscaping, and more
Engage in strenuous or endurance activities
Have underlying health conditions that affect their electrolyte balance, including adrenal insufficiency, kidney disease, or diabetes

For these groups, deliberate electrolyte replacement is especially important.

Sports drinks

How about those sports drinks, though? Dr. Nystrom says they aren’t enough. “One of the most common myths I see in the ER is that patients and parents of sick children think that Gatorade, Pedialyte, etc., actually rehydrate.” However, the math doesn’t math for these. “None of those drinks actually have enough electrolytes to compensate for losses from sweating or gastrointestinal losses (vomiting and diarrhea),” he adds.

“The volume of sports drinks you would have to drink to replace electrolytes is counterproductive because of the high volume of water-to-electrolyte ratio in those products.”

What’s the Fastest Rehydration Checklist to Follow Right Now?

For mild dehydration, drink fluids according to thirst and estimated losses. After substantial sweating or gastrointestinal fluid loss, an appropriate electrolyte-containing beverage or ORS may be useful.

Here’s what I do when I need to rehydrate fast: Sip a 32-oz glass of water with one electrolyte drink mix packet or a gram of salt and avoid plain water for two hours. Experiment and watch for your symptoms to improve, but seek medical help if they don’t improve within two hours.

If you are experiencing mild to moderate dehydration, you can use this checklist or protocol to address the issue.

Sip one glass of water with one electrolyte packet to start. Add a pinch of salt to water if you do not have electrolytes available.
Watch for symptom improvement within one to two hours, and seek help if your symptoms are not improving.

How Long Does It Take to Rehydrate Your Body?

The time it takes to rehydrate your body varies, from an hour or two to several days, depending on how severely dehydrated you are, what caused the dehydration, your activity levels, and your body’s balance of electrolytes. It can take roughly 2-3 hours to rehydrate with water and electrolytes when I’m feeling mildly dehydrated, but moderate dehydration can require a day or more to rehydrate, and severe dehydration takes several days to address, sometimes requiring medical care.

Rehydration speed isn't fixed — it varies with the severity of fluid loss, the sodium content of what you're drinking, how quickly your stomach empties into the small intestine, and how hot the environment is.

When Should You See a Doctor for Dehydration?

If you experience confusion, fainting, a rapid heartbeat, no urination, or persistent vomiting, electrolyte drinks are not enough, so seek medical care right away. Babies need to see a doctor if they have fewer than three wet diapers in 24 hours, cry without tears, or have a sunken soft spot on their head, and older adults should seek medical care if they have sudden weakness, confusion, or low blood pressure.

When someone seeks medical attention for moderate dehydration, the ER staff might start with oral rehydration, if the person can tolerate it, as Dr. Nystrom explained. But people who come in with low blood pressure and a rapid heartbeat will typically receive IV fluids — often containing about 3,000–3,500 mg of sodium per liter — over 30 to 60 minutes, Dr. Nystrom said.

What Are Best Practices for Staying Hydrated?

You can stay hydrated and avoid dehydration through several best practices that include eating water-rich and potassium-rich foodsOpens in a new tab, ensuring you get enough sodium, and drinking enough fluids before, during, and after a workout.

Some situations, such as my sweaty jiu-jitsu training, can make it more challenging to avoid getting dehydrated. But I’m super diligent now to stay as hydrated as possible to avoid dizzy spells or performance dips.

Here are a few strategies to consider for maintaining hydration throughout the day:

Incorporate water-rich foods, including cucumbers, melons, tomatoes, celery, citrus fruits, and more.
Eat potassium-rich foodsOpens in a new tab, including avocados, bananas, oranges, sweet potatoes, spinach, broccoli, squash, beets, and certain beans and legumes.
Sprinkle your favorite type of salt on your food — only about 11% of the sodiumOpens in a new tab in your diet comes from the salt you add during cooking or at the table.
Add a pinch of salt to your water when the mood strikes.
Hydrate before spending time in the heat or before a workout by consuming water with electrolytesOpens in a new tab.
Rehydrate after being in the heat or working out by consuming water with electrolytes.
Drink fluids and electrolytes during a workout — the recommendation from the American College of Sports Medicine and the National Athletic Trainers’ Association is to consume about 200 milliliters (about 7 ounces) of fluid every 15 to 20 minutesOpens in a new tab, though individual needs will vary.
Consider a magnesium supplementOpens in a new tab — the prevalence of magnesium deficiency reported in the U.S. based on lab tests ranges from 2.5 to 15%Opens in a new tab, but about 45% of AmericansOpens in a new tab have inadequate magnesium intake

Keep in mind that staying hydrated does not prevent all concerns with working or working out in the heat. “Those are different processes going on in the body,” says Dr. Nystrom, “and although adequate hydration is helpful, hydration alone does not prevent heat exhaustion or heat stroke.” Acclimatization, clothing choices, and environmental monitoring are all important in avoiding heat stroke, which is a neurologic emergency — not just a symptom of dehydration.

"Best Practices for Staying Hydrated Incorporate water-rich foods (like cucumbers, melons, tomatoes, celery, citrus fruits) Eat potassium-rich foods (like avocados, bananas, oranges, sweet potatoes, spinach, broccoli, squash, beets, and certain beans and legumes) Sprinkle your favorite type of salt on your food Add a pinch of salt to your water Hydrate before/after spending time in the heat or before/after a workout by drinking water with electrolytes Consider a magnesium supplement"

Key Takeaways — What’s the Fastest Way to Rehydrate?

To rehydrate fast, you should consume fluid with an optimal amount of electrolytes, but if you’re experiencing severe dehydration, you need medical attention.
Your body becomes dehydrated when you lose too much fluid for it to keep functioning properly, resulting in potential symptoms of fatigue, lightheadedness, thirst, muscle cramping, and more.
Fluid loss can also flush out your body’s electrolytes, which are crucial for nerve and muscle function and more.
Your speed of rehydration will depend on several factors, including why you’re dehydrated and how much fluid and electrolytes you’ve lost.

Frequently Asked Questions About Rehydrating Fast

Q: What is the fastest way to cure dehydration?

The quickest way to cure mild-to-moderate dehydration on your own is to consume water with an optimal amount of electrolytes, including sodium, chloride, potassium, and magnesium. The fastest way to cure severe dehydration, which is a medical emergency, is with IV fluids.

Q: How long does it take to rehydrate your body?

Rehydration if you are mildly or moderately dehydrated can take 45 minutes to several hours, depending on how dehydrated you are, your electrolyte status, why you became dehydrated, and other factors. More severe dehydration can require several days to get your body fully rehydrated.

Q: How do you hydrate your body as fast as possible?

To hydrate your body as fast as possible, consume water with optimal amounts of electrolytes, including sodium, chloride, potassium, and magnesium. If you’re experiencing severe dehydration, you may need IV fluids to hydrate your body as fast as possible.

Q: What are the warning signs of dehydration?

The warning signs of dehydration include dry mouth or throat, dark or less frequent urine, fatigue, headache, dizziness, nausea, weakness, and muscle cramps. You may also have dry skin and experience substantial drops in physical or cognitive performance.

Signs of severe dehydration, which requires immediate medical attention, include a rapid heartbeat (tachycardia), confusion, fainting, hallucinations, high fever, loss of consciousness, seizures, hypotension (low blood pressure), unusually dark urine, or lack of sweating even when you’re hot.

Q: What hydrates you faster than water?

Consuming water with electrolytes — sodium, chloride, potassium, and magnesium — will hydrate you faster than drinking plain water by itself. You can make yourOpens in a new tab own mixture of water with electrolytes or use LMNT or another electrolyte drink mix.

Q: Is water alone enough to hydrate quickly?

Plain water will not hydrate you as quickly as water with added electrolytes. Drinking water is fine for general everyday thirst, but if you are experiencing mild or moderate dehydration, using LMNT or another electrolyte drink mix can help you hydrate faster than drinking water alone.

Q: Are sports drinks better than water for quick hydration?

Sports drinks usually have a small amount of sodium and often have high levels of sugar, which may be more helpful than plain water for light activity where some extra carbs are useful. Sports drinks might rehydrate you a little faster than plain water, but for more strenuous exercise or any activities involving a lot of sweating, drinking water with a meaningful amount of electrolytes — roughly 500–1,000 mg of sodium per liter — can often be the fastest way to rehydrate.

Q: Can I hydrate quickly with water-rich foods?

You cannot rehydrate quickly by eating water-rich foods because fluid absorption is slowed downOpens in a new tab as your body digests the foodOpens in a new tab. Regularly eating water-rich foods might help you avoid getting dehydrated or slow down how fast you get dehydrated, but hydrating quickly requires consuming fluids, ideally water mixed with electrolytes if you are already mildly dehydrated.

Q: Can dehydration cause nausea?

Yes, nausea is a common sign of dehydrationOpens in a new tab, and severe dehydration can result in vomiting. Other common signs that you are mildly or moderately dehydrated are a dry mouth or throat, infrequent urination or dark urine, headache, fatigue, dizziness, weakness, and muscle cramps.

Updated August 2026