Sep 20, 2015 | Uncategorized

Hydration for Runners

Last summer I hit on the ideas of hydration and overhydration, as general recommendations on hydration. Today, I want to dive in a little deeper and talk about hydration and electrolytes for runners.

Yesterday, I completed the big 20-mile training run, as part of my preparation for the 2015 Chicago Marathon. Want to know more about why I’m running? Check out my fundraising page here. Yesterday’s run reminded me of what a difference 20 degrees makes. Two weeks ago, the temps and humidity were up. Yesterday was perfect running weather. My experiences couldn’t have been more different.

An early fall marathon means intense summer training. Some of you are used to painful heat and humidity – Houston (Tex.) and Richmond (Va.) come to mind – but this has been my first running experience with both real heat and real humidity. Dallas was hot, don’t get me wrong, but less humid. Plus, when it’s 90 degrees at 6am, who is really splitting hairs over whether it’s the heat or humidity that’s sucking the life out of you?

Staying properly hydrated during a training run or a race can make the difference between finishing and not, or the difference between Boston-qualifying, and “better luck next year”. Like most things for endurance athletes, cramming won’t cut it. Just like you can’t jump from 5 miles to 25 miles, you shouldn’t start a run dehydrated and just drink a gallon of water on your run.

Days Before

Make sure you’re getting in enough water before the long run. Wondering how much that is? Review adequate hydration here. For those of you who are regularly training, especially in the summer, this just boils down to ALWAYS thinking about hydration. The good news is that it will eventually become second nature. But it might take some intentional efforts in the beginning. Check out Pinterest for inspiration on flavor-infused water.

An Hour Before

About an hour before the run or race, aim for 16 ounces of water. This is equivalent to 2 cups or a pint glass of water. Drinking more water, or drinking it too much later will likely just cause you to have to pee – depending on travel time to the race, this may be inconvenient.

During the Run

Everything should be customized to you knowing your body, but a good rule of thumb is 4-6 ounces of water for every 20 minutes of activity. A little more if you’re a fast runner (less than 8 minutes/mile). Another way to think about it that doesn’t involve math: grab a cup of water at aid stations every 2-3 miles.

A hot and humid day is going to require more, while a cooler or less humid day will need less. Two weeks ago, I needed about 2 liters of water to feel good. Yesterday, I ran longer but needed only about half as much.

After the Run

Depending on how things went on the run, you want to drink between 8-20 ounces for recovery. You should need to pee within an hour of finishing. Keep up the hydration until your urine is the desired light yellow.

Sweat Rate

The above is definitely a general recommendation, and a good place to start. But that doesn’t mean it’s universal information that will work perfectly for everyone.

One way to think about how much water you need is to find out how much water you’re losing. This is also called your sweat rate. Most people know intuitively if they are heavy sweaters or not. But to get more scientific about it, you simply need to weigh yourself before and after your run. You want to do this without wearing any clothes (sweat on your clothes will add weight).

One pound of weight loss is equal to 16 ounces of water. Say you run for 2 hours, and come home to discover you’ve lost 2 pounds. What does that mean? You lost 32 ounces over 2 hours (about 1/4 ounce per minute). For now, drink those 32 ounces! For future reference, the next run in similar conditions will require an additional 4 ounces each 15 minutes to maintain good hydration. 

Doing this test a couple of times can help you fine-tune your personal water needs. Also, you’ll learn how to get the amount of fluid in your system without feeling it sloshing around during a run. For instance, drinking 8 ounces every 30 minutes might feel really different than 4 ounces every 15 minutes, even though you’ll end up drinking the same amount of water.


For workouts under one hour, electrolytes aren’t usually a significant factor. Water should do the trick for you, and normal eating patterns will replace any losses. But once you get into the longer runs or rides, you need to replace mid-workout.

But remember, each person has a different rate of sweat, and a different amount of electrolytes lost in their sweat. If you find your skin or clothes caked in white deposits or sweat lines after a run, you need to pay special attention to electrolytes.

Activity lasting 1-4 hours requires some electrolyte replacement. You can get this in the form of a sports drink (Gatorade, Powerade), tablets (Nuun, SIS), gels (Cliff Shots, PowerBar Gel), or a homemade concoction.

The sports drinks, tablets (diluted according to instructions), and homemade concoction can all be consumed in place of water. You’re getting 2-for-1 hydration and electrolytes. If you are choosing gels, add about 1 per hour. You want to front-load them, meaning you have one at the beginning of each hour, not the end (i.e. at the start of the run and 1 hour into it for a 2-hour run). To avoid cramping, bloating or other GI distress, make sure to drink water with it as part of your hydration plan.

Bring it with You

If you’re not competing in a supported race, you’re most likely out and about, responsible for your own water – those aid station tips aren’t going to help you out. Find the hydration system that works best for you, whether it’s a belt or a backpack.

For runs over 10 miles, I love my hydration backpack. I’ve been made fun of plenty for it. Some people have said I look like I’m in basic training, or taking things too seriously. But for me, being able to take a sip or two at a time is a convenience that I appreciate. Plus, my “look” while I run isn’t my top concern. Additionally, my pack has pockets that I can access while I’m moving, where I store my fuel, keys and phone. Here is the updated version of mine.  

Don’t forget – these are general recommendations. If you find yourself struggling to get it right, or want more professional advice, contact me or find a dietitian in your area.

Want to learn more about pregnancy or prenatal nutrition?
Schedule your free discovery call today!



Motherhood doesn’t have to be so complicated. Schedule your free discovery call today!



I’m Katie Goldberg (AKA The Pregnancy Dietitian), mom of 2 little humans, health coach, and registered dietitian nutritionist. I can guide you through the research and best practices (and avoid all the B.S.) to help you confidently nourish your body and your baby during this unique season of life.

Get your Free guide!


Not all prenatals are equal and deciding which is best for you can be difficult.

Download my FREE guide to help simplify the process.


The Ultimate Guide to Prenatal Vitamins

The Ultimate Guide to Prenatal Vitamins

It’s probably not news to you that you should take a prenatal vitamin. Many OB/GYNs encourage taking one before you are pregnant, and it’s certainly addressed at the first appointment. But beyond “you should take one,” do you really know how to choose one? How do you...

Protein Needs During Pregnancy

Protein Needs During Pregnancy

Did you know that protein needs increase during pregnancy? Since many women experience some form of food aversions or nausea, getting in enough protein can feel a bit daunting. Let's talk about how much protein you really need, and how to make that happen when you're...

How Much Water Should You Drink During Pregnancy?

How Much Water Should You Drink During Pregnancy?

We've all heard that it's important to stay hydrated. But how much water should you drink during pregnancy? Does that 8 glasses a day rule still apply? And do other liquids count, or just water? Once again, something that has always felt pretty simple, is suddenly...

Pin It on Pinterest

Share This