Marathon Hydration

Marathon Hydration

I have run 20 marathons and have learned what hydration plans work and don’t work for me during a race. I have run multiple races in India, where I was already sweating in the start corral and races in the desert with 20% humidity. I live in Minnesota, where it can be -20f and 100f. Here are my experiences with hydration and nutrition in the marathon.

Hydration is the most important thing you need to pay attention to before, during after your marathon. Everyone’s body is different, and everyone will react differently during training. Marathon hydration is even more important and sometimes tricky to figure out. Here are some helpful tips that have worked for me and some that don’t work. Remember, everyone is different, and everybody has different needs. I am covering marathon hydration and nutrition here with a focus on Tailwind Nutrition. The following are items of which I have had success.

Pre-race marathon hydration

It is essential to stay hydrated while you are training. If you are in a hot climate, you need to take even more liquids, electrolytes, and carbohydrates. A good rule of thumb is to weigh yourself before and after a long run. Before I realized the importance, I would find myself down as much as 10 pounds after a long hot run! Because heat and humidity affect the amount of water you lose, there is no exact formula on what you need.

Calculating sweat rate

  1. Urinate, then weigh yourself completely naked. (A)
  2. Run and record any water you drink (i.e., I drank 500ml of water). If you want to get exact (As described on TrainingPeaks), you can weigh the water you didn’t drink as well.
  3. Weigh yourself again (Naked!)
  4. Your weight loss will be C=A-B
  5. 1 liter of water equals 1kg (Z)
  6. Your calculated sweat rate will be (C+Z)/time

The entire process is described on the TrainingPeaks Blog here

Calculating sweat rate and understanding a general number for yourself can help you make small adjustments. Testing yourself in “average” conditions will allow you to scale up or down depending on race conditions.

Meghan Peyton, professional runner and coach

Always drink water (When not running)

Pre marathon hydration needs to start every day you run. Make sure you have formed a good habit of drinking enough water daily. The Mayo Clinic recommends the following:

  • About 15.5 cups (3.7 liters) of fluids a day for men
  • About 11.5 cups (2.7 liters) of fluids a day for women

As you exercise, you need to supplement the above numbers. You will need water, even if it’s cold out. You will still sweat!

Race Day

The following are some items that I have had success with marathon hydration on race day. I have had plenty of fluids the week up to the race. I stopped drinking alcohol or at least drastically cut back. The morning of the race, I would have an 8oz cup of coffee and water. I would also mix up a 16oz bottle of Tailwind (non-caffeinated), and I would drink this 45 minutes before starting the race. My goal is to have to pee right before the start of the race, and this will tell me that I have adequately hydrated. (At least for my body).

My coach Meghan Peyton recently told me that I should be taking nutrition sooner in the race than I had been doing. Traditionally I might wait until 45 minutes to take some nutrition. To help combat this, I have run with a 2-liter hydration pack but will add a considerable amount of weight. On the plus side, your hydration pack allows you to “Sip” as needed and stay hydrated. The other option I have done with Tailwind is to concentrate the mixture into my two 16 oz water bottles that I carry on my belt. You can even get smaller “flasks” that you can focus your mix even further. The goal is to start fueling and not put your body into a nutrition deficit or, even worse, a marathon hydration deficit.

How much and how often?

How much water do you need to have success in your marathon hydration plan? What you need is up to your body and how it reacts to the environment on that day. Drink when you feel thirsty is the first thing, and take some nutrition along with your water.

Elite runners have the luxury of having their bottles out on a table. As a non-elite, I have to carry it with me or depend on the race to have what I need. I try to drink at least every other water stop and take nutrition every 45 minutes. I will do this to the end of the race.

To much water (Hyponatremia)

You can drink too much, and this can be dangerous. Hyponatremia occurs when the concentration of sodium in your blood is abnormally low. I avoid this by taking electrolytes in my drink but also as supplements. I also avoid drinking water at every water stop.


Tailwind does include electrolytes, but if you are going to drink only water, you will want to consider another electrolyte source. Most gels and blocks have electrolytes, and you can also get electrolytic tablets. Races also typically offer some sports drink that includes electrolytes. My only caution is that you should know what the drink is, and you should have tested it during one of your long runs before taking it in a race.

Know when you are dehydrated

The Mayo Clinic states one of the most common causes of dehydration is vigorous exercise during hot weather. One of the best ways to combat dehydration is to drink water! When you are thirsty, you are slightly dehydrated already, so a good hydration plan is vital. Dehydration can cause fatigue and happens at the end of your marathon. Watch out for these subtle indications and take care to drink enough water. Additional signs can include dizzyness and confusion. The best defense against this is to practice your marathon hydration strategy during your training runs. And always remember, you can get dehydrated when it’s cold out.

Caffeine or not?

Tailwind writes your name on your package!

I have tried all sorts of caffeinated gels, blocks, and liquids during my marathons. In 2017, I ran the Berlin Marathon and the Chicago Marathon two weeks apart. In both races, I thought taking caffeine during the entire race was the right choice. In both races, at about the 2.5-hour mark, I felt my chest tighten and ended up dumping out any liquids I had left that were caffeinated. In my recent race in Nevada, I had a small Tailwind Colorado Cola bottle that I started taking after 21 miles. This combination worked great for me, and I had a huge PR and worked for my marathon hydration plan.

Everyone is different, and everyone reacts differently to caffeine. I get the most significant benefit as a boost towards the end of my race. You can try this with caffeinated Clif Blocks or even Hammer Gels (I like these)

Whether you want something in your drink or you take a gel, the goal is to get an energy boost towards the end of your race.

Post race marathon hydration

I have started using the Tailwind rebuild recovery drink after a long run and especially after a marathon. I will put a shaker bottle into my drop bag and a serving of the recovery drink and mix some water that I get at the finish. It is a great way to get some post-marathon hydration along with some protein.

The rest of your day

Your dehydration levels are different depending on your race and the day. It is important to drink plenty of fluids throughout the day. My goal is to get myself to urinate a couple of hours after the race. Typically, I can go to the bathroom once, but it could take sometime later into the day. If your urine is dark yellow, you are dehydrated. I limit the amount of alcohol and coffee I drink after a long race and focus on water. (I might have a coke or iced tea)




4 responses to “Marathon Hydration”

  1. Great tips from someone who has clearly learned lots of lessons along the way. I have played with the caffeine combo. I learned it works towards the end, let’s say miles 19 and then every 30 minutes or longer to get the “wake up call” but anything before that just jacks me up. Great blog post!!

    1. Thank you, Janice! Go Fly Girls!

  2. It is very a pity to me, that I can help nothing to you.

  3. Amusing state of affairs

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