Dehydration Red Flags That Every Runner Should Know

Ashley Lauretta
by Ashley Lauretta
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Dehydration Red Flags That Every Runner Should Know

Here’s an alarming statistic: Studies show that 75% of Americans are walking around dehydrated. If you fall into that category — and you’re a runner — starting a workout in a dehydrated state may mean you are putting yourself in danger.

Dehydration is a much talked about issue in the summer months, but the truth is, you can get dehydrated no matter the weather. Your sweat rate and heat have an impact, of course, but aren’t the only contributing factors.

The recommendations of how many cups you should drink per day often vary, but there is a simple rule of thumb you can follow to help stay hydrated. “Drink when you are thirsty,” states Jess Underhill, a running coach and founder of the Race Pace Run Club. “Listen to the cues your body is giving and — if you are a runner — don’t ignore them in lieu of running a faster mile or saving time by not making a pit stop for a water fountain.”


There are some telltale signs of dehydration — and the easiest one to recognize is thirst. Being thirsty may seem like a normal part of everyday life, but you should be drinking enough water throughout the day that you don’t feel the need to chug water to satiate yourself.

“Feeling thirsty happens after you are dehydrated,” explains Dr. Martha Pyron, MD of Medicine in Motion. “You should try to prevent feeling thirsty.”

Other common symptoms of dehydration include fatigue, dry eyes, dry mouth, cramps, headache and muscle spasms. Underhill also notes that runners may notice they may stop sweating while on a run when they previously were sweating.

These, of course, are all of the signs of dehydration that you may experience as it sets in, however, it is important to know that there are more serious effects that can be felt should the issue not be addressed as soon as possible.

“Even moderate dehydration can cause fainting, confusion and convulsion,” adds Dr. Billy Holt D.O., owner of VIP Medical Services. “Dehydration can rapidly progress to heat exhaustion or heat stroke that can lead to hypovolaemic shock and ultimately death.”


You can feel the effects of dehydration long after you first experience symptoms, which can impact your day and, in a runner’s case, any workouts you have planned that day or even that week. The amount of time you’ll notice an impact depends on how severe your dehydration and resulting symptoms were.

“If the rehydration process is not started after the run, dehydration can continue to negatively impact the body for hours or even days after the workout,” notes Dr. Holt. “This is why regular everyday hydration is important, but also pre-, mid-, and post-workout hydration, as well.”

It should be noted that dehydration can have negative consequences for your recovery from a workout, as well. Underhill explains that because of this addition to the length of recovery, your next day’s workout will be impacted.

This is all in terms of dehydration that is resolved quickly. If you have severe dehydration that leads to heat stroke, for example, the effects will be felt much longer.

“If you push yourself into full-on heat stroke, it could take weeks for your body to recover — and it may not completely recover,” shares Dr. Pyron. “Dehydration can affect the rest of your athletic career, especially if it is severe enough to lead to heat stroke.”



Dr. Holt reiterates that you always want to stay hydrated for optimal health and body function, and for runners, this means replenishing fluids after any exercise. This doesn’t necessarily mean just drinking water, however.

“It’s important to replace fluid loss and replenish glycogen stores after a run to diminish the impact of dehydration,” adds Underhill.

Though most people are OK to drink just water, if you are running long distances or are new to physical activity, you’ll want to add an electrolyte drink to your hydration routine during and post-run.

“Electrolyte drinks may be needed to keep salt levels in balance,” explains Dr. Pyron. “If you sweat out salt water and only replace it with pure water, you may change the salt concentration in your blood, which can also be bad. So, an average solution is to drink every third drink as an electrolyte drink and the rest can be water.”

It is also important to note that it is absolutely possible to drink too much water, which is known as hyponatremia. Underhill explains that this is a serious medical condition that occurs if there is too much water in the body and not enough sodium. Due to the effects, overhydration can be just as dangerous as dehydration.

To avoid taking in too much water during or after a run, knowing your sweat rate — on hot days especially — can help you meet specific hydration needs. “In order to do this, you need to weigh yourself immediately before your run, keep track of your fluid intake during your run and then weigh yourself immediately after your run,” notes Underhill. “Then, you calculate your sweat rate using this formula: Pre-run weight in ounces – post-run weight in ounces + fluid intake in ounces during your run = your sweat rate.”

About the Author

Ashley Lauretta
Ashley Lauretta

Ashley is a journalist based in Austin, Texas. She is the assistant editor at LAVA and her work appears in The Atlantic, ELLE, GOOD Sports, espnW, VICE Sports, Health, Men’s Journal, Women’s Running and more. Find her on Twitter at @ashley_lauretta.


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