Staying properly hydrated can enhance your running performance—or derail it completely if you don’t get it right. Too little, and you’re dragging through miles, dizzy, fatigued, and cramping. Too much, and you’re dealing with stomach slosh or, in extreme cases, hyponatremia (we’ll get to this later).
For short runs, you don’t need to overthink it. Unless it’s blazing hot and humid out, you can just replenish fluids afterward. But once you start logging longer miles, hydration becomes a crucial part of your training and racing strategy.
I personally make sure to drink water on any run over 60 minutes—it keeps me feeling strong and avoids that dreaded post-run dehydration headache.
And yes, there’s such a thing as too much water. Overhydrating can throw off your electrolyte balance, leading to nausea, bloating, and, in extreme cases, serious medical issues.
So, how do you strike the right balance?
In this guide to hydration for runners, we’ll break down exactly how to fuel your runs with the right amount of fluids and electrolytes, so you can stay hydrated and energized for your long runs, workouts, and races.
How Much Water Should Runners Drink Daily?
The daily water intake for runners will vary and depends on a few different factors such as body size, training volume, sweat rate, and climate, but here are some general guidelines:
General Baseline Hydration
A good starting point for staying well-hydrated is the general recommendation of 8–10 cups of water per day. From there, you can adjust based on the factors above.
If you engage in high-intensity exercise, run long distances, or live in a hot and humid environment, your fluid needs will be higher to compensate for increased sweat loss.
Keep in mind that hydration isn’t just about plain water—fluids from sources like coffee, tea, milk, juice, and even water-rich foods also contribute to your daily intake.
Listen to your body and stay proactive in replenishing fluids throughout the day.
Prehydrating Between Intense Workouts and Races
If it’s been less than 12 hours between intense workouts or races, you’ll want to pre-hydrate about 4 hours prior.
For pre-hydration, slowly consume 0.17-0.23 oz (5-7 ml) of fluid per 2.2 lb (1 kg) body weight. This is roughly the equivalent of a large glass of water for a 165 lb. (75 kg) person.
If you are concerned about hydration during your workout or event, you can add some sodium-containing snacks or fluids with your pre-hydration routine to help with water retention.
Do you always need to pre-hydrate? Not necessarily—if it’s been more than 12 hours since your last workout or you’re already well-hydrated, extra pre-hydration isn’t crucial. However, checking in on your hydration status before a hard run or race is always a smart move.
How to Measure & Match Your Fluid Needs During Exercise
If you’re looking for an actual quantity of recommended fluid so you can plan your hydration needs in advance, here’s the average consumption:
In general, it’s recommended that athletes aim to drink 0.4-0.8 liters per hour (L/h) or 8-16 ounces per hour (oz/h). To get even more precise, you can calculate your sweat rate.
How To Calculate Your Sweat Rate
New technology, like the Nix Hydration Biosensor, now allows athletes to track sweat and electrolyte loss in real-time. This wearable patch monitors hydration levels during exercise and sends live data to an app, helping runners and endurance athletes stay ahead of dehydration and electrolyte depletion.
For those who don’t have access to this type of technology, a simple at-home sweat test can provide a general idea of how much fluid you lose per hour, helping you fine-tune your hydration strategy.
Understanding your sweat rate helps you dial in your hydration strategy so you can avoid dehydration and overhydration during long runs and races.
Here’s how to calculate your sweat rate with a simple 1-hour sweat test:
Sweat Test
- Weigh yourself before your run without your cloths or shoes on.
- Record your weight.
- Run for 1 hour at a typical training pace. During your run, do not consume or expel any liquid…so in simpler terms: no drinking or peeing! This will throw off your calculation.
- Towel off and weigh yourself again: Immediately after finishing, towel off excess sweat and weigh yourself without clothing.
- Record your post-run weight.
- Calculate your sweat rate.
Use this formula:
Sweat Rate (oz/hr) = Pre-run weight – Post-run weight
Take your pre-run weight and subtract your post-run weight. The outcome will be the amount you sweat per hour while you run. Let’s take a look at a couple of examples:
Pounds:
125 lb. (pre-run weight) – 122 lb. (post-run weight) = 3 lb. = 48 oz per hour
Kilos:
50 kilos (pre-run weight) – 48.5 kilos (post-run weight) = 1.5 kilos = 1.5 liters per hour
If you are calculating this for race day, try to replicate conditions so you can estimate your fluid needs for the temperature and humidity you’ll likely experience.
How Often Should I Drink Fluids While Running?
It’s important to remember that some dehydration is normal during prolonged exercise, and attempting to replace your exact fluid quantity during exercise can be counter-productive and lead to stomach slosh: follow the sip rule and rehydrate the rest when you cross the finish line.
This means sipping your fluids instead of chugging them down. You want a constant flow of hydration instead of consuming it in large quantities all at once.
You can set alarms on your running watch for every 10 minutes or whatever time interval feels right for you and take a sip. This way, you won’t forget.
The goal after a workout, long run, or race is to replace lost fluids to maintain proper hydration and prevent dehydration.
Ideally, your post-run weight should be the same as your pre-run weight, meaning you’ve replenished fluids at a 1:1 ratio to what was lost (this also includes what you replenish after your run, as consuming 100% during a race or workout is nearly impossible for most).
If electrolytes were depleted, be sure to restore those as well before transitioning back to your regular daily hydration routine.
What Are Electrolytes?
When your sweat rate begins to increase, you’ll want to start adding essential minerals (called electrolytes) to your hydration routine and fluid intake to replace lost minerals in sweat loss.
You know how sweat is salty? It’s because you’re excreting these minerals.
Electrolytes are minerals considered essential for proper functioning of the human body and they are often lost through sweat. They are essential for cellular function and help to regulate pH in the body, and for proper nerve and muscle function (including the heart muscle).
Electrolyte minerals exist as charged ions and include sodium, calcium, magnesium, and potassium (some lists include chloride and phosphorus as well).
#1: Sodium
Sodium helps regulate proper fluid and electrolyte mineral balance so you don’t get dehydrated. It also assists with muscle contractions and nerve function.
#2: Potassium
Potassium is used in various vital bodily functions, such as regulating fluid and electrolyte balance, nerve signals, and muscle contractions. It also promotes glycogen storage and aids in the transportation of nutrients.
For us runners, if we don’t have enough potassium, it will be impossible for our muscles to properly contract, leading us to cramp up.
#3: Magnesium
Magnesium is used for energy production, metabolism, muscle and nerve contractions, muscle recovery, and general bone health.
It also helps avoid cramping.
With increased sweat rate, there is an increase in loss of these minerals.
The amount of sweat people lose during workouts can be highly individual, as well as the mineral makeup of their sweat. Some people’s sodium levels dip lower than others when they sweat, so it’s important to learn more about your body’s individual sweat rate.
If you know that you’re going to be doing a race or event in a hot and/or humid climate that you’re not used to, take some time to acclimate yourself beforehand to not only perform better, but also to help your body adjust to new hydration needs.
Hydration For Runners: The Best Options
There are many different hydration options available to runners and fitness enthusiasts, and sometimes choosing can be overwhelming.
But we’re going to break down the main types of hydration products available and what products are best for you and your fitness needs.
When Does Just Plain Water Do The Trick?
Plain water is the best thing to start with for regular daily hydration. For most people and recreational exercisers, plain water will suffice for hydration if your workouts are:
1) Moderate in intensity
2) Last less than 1 hour
3) Are in cool temperatures and low humidity
When Should You Add Electrolytes?
Once you start to increase your workout length, intensity, ambient temperature, or humidity, your hydration needs change based on an increased sweat rate and greater loss of electrolytes and minerals through your sweat.
When any (or all) of these factors change and your sweat rate increases, you’ll need to start adding electrolytes to your hydration regimen to replace lost minerals since water alone won’t be enough.
Electrolytes come in several different forms for you to choose from:
- Pre-mixed drinks (Nuun Instant, Gatorade, Powerade, Propel, Pedialyte Sport)
- Powders or tablets you mix with water (Nuun Sport Tablets, Tailwind Nutrition Endurance Fuel, Skratch Labs Sport Hydration Mix, GU Roctane Energy Drink Mix)
- Capsules you swallow as a supplement (SaltStick Caps, Hammer Nutrition Endurolytes, GU Roctane Electrolyte Capsules)
- Chewable tablets (SaltStick FastChews, Nuun Instant Quick Hydration, GU Energy Chews, Skratch Labs Energy Chews)
- Electrolytes mixed into energy chews and gels (Clif Bloks Energy Chews, GU Energy Gels, Honey Stinger Energy Chews, Maurten)
The type of electrolyte you choose will depend on your workout, your palate, your fueling needs, and how you plan to carry your hydration during your workouts.
Also, every brand of electrolyte replacement has a different formulation. Some brands will have more sodium, others will have more potassium, and still others will have trace minerals like selenium and copper (I’ve found my body really likes these ones).
Try out and research a variety of different brands to see which ones work the best for your body.
Most electrolyte powders have a sugar-free option, so if your workouts aren’t long or you plan on having a separate fueling plan with carbohydrate chews, gels, or actual food, then the sugar-free electrolyte drink mixes will work well for you.
If your workouts are going to be long and you will be able to refill a water bottle, it’s great to keep electrolyte drink mix packets or tablets (like Propel or Nuun) with you to add to water at your convenience.
If your workout isn’t going to be long, but you need electrolytes because it’s hot or you’re a heavy sweater, then you can take a small bottle of pre-mixed electrolytes with you or a few electrolyte chewables if you’re not taking very much liquid with you.
It’s important to note that while you may like the idea of a chewable tablet or capsule, if you’re running a race, you might not be able to stomach a chewable or be able to easily swallow a capsule.
Make sure to always train with your planned hydration methods before racing. Don’t try new electrolyte or hydration methods during a race that you haven’t tried beforehand during training sessions.
Remember: this all takes practice to figure out an electrolyte replenishment strategy that will work for you. Have some fun trying out some new methods and brands during your training runs to see what works best.
Related: How Frequently Should You Take Energy Gels During Races?
Sports drinks that contain carbohydrates and sugar
Sports drinks that contain carbs can be a useful fueling tool for endurance running, but they aren’t always necessary for every workout. If you’re running for less than 90 minutes at moderate intensity, plain water is usually sufficient.
However, for long runs over 90 minutes or races, sports drinks can provide easily digestible carbohydrates and electrolytes to help sustain energy and maintain hydration levels.
When choosing a carbohydrate-based sports drink, look for one that contains multiple types of sugar (such as glucose and fructose), which allows for better absorption and reduces the risk of stomach distress.
Keep in mind that not all sports drinks are created equal, and certain sugars—especially fructose—can be difficult to digest for some runners, particularly those with IBS or sensitive stomachs. Testing different brands and formulations during training will help you find what works best for you.
If you struggle to consume solid foods, gels, or chews during long runs or races, sports drinks can be an effective alternative to meet your carbohydrate fueling needs.
However, be mindful not to overload on carbs all at once, as consuming too much too quickly can lead to GI distress and an upset stomach while running. Instead, space out your intake and factor sports drinks into your overall fueling strategy to maintain steady energy levels.
The key to using sports drinks effectively is to plan ahead, experiment in training, and listen to your body.
What Are The Risks of poor hydration?
Making sure that you pay attention to your hydration is not only important for optimal athletic performance, but it’s crucial to your health and wellbeing.
Dehydration
Most people aren’t going to get dehydrated to the point of serious health consequences or death, but many do experience signs of dehydration like lethargy, muscle cramping, dizziness, confusion, dark urine color, high heart rate, increased body temperature, etc.
Mild dehydration (1%-2% loss of body weight) is normal during exercise, especially during endurance events like marathons.
But your goal should be to manage mild dehydration and keep it from becoming severe dehydration that can result in serious complications like seizures.
What Are The Signs Of Dehydration In Runners?
Other symptoms of dehydration include:
- Dry mouth and excessive thirst
- Dark yellow urine
- Dizziness or lightheadedness
- Elevated heart rate
- Reduced sweat production
- Nausea or stomachache
- Decreased performance
- Fatigue
- Muscle cramps
- Headache
Is Overhydration A Concern For Runners?
Hyponatremia
One aspect of hydration that people don’t often address is hyponatremia, which is overhydrating.
Hyponatremia is defined as an abnormally low concentration of blood sodium and it can occur when someone drinks too much low-sodium fluids over long periods of time compared to their sweat rate.
The greatest predictor of hyponatremia is an increase in weight during the duration of a workout, meaning you have consumed an excess of fluids.
Runners who are exercising at low to moderate intensity for long periods of time and who have a low body mass index are more susceptible to hyponatremia, while high intensity exercisers are more likely to suffer from dehydration.
To prevent this, make sure that you are consuming moderate amounts of liquids for your needs during exercise, and you are also including sodium and electrolytes in your hydration routine when you’re running for longer periods (over 1-2 hours)
How Can I Prevent Dehydration While Running?
Once you’ve figured out how you want to stay hydrated for your training runs and races, the next task is figuring out how you can stay hydrated during your runs.
Here are some hydration tips so you can plan for your running workouts or races:
- Plan out your route to go by places with water (like drinking fountains). If you need to do a longer run but can’t carry water with you, create loop routes where you can come back to a water bottle regularly.
- Check out running vests, running belts, and handheld bottles to take with you so you never lack the necessary amount of fluid you need to stay hydrated.
- Ensure you are hydrated on a daily basis to support not only your running, but overall health.
For more information on electrolytes, check out this next guide:
