Running and Electrolytes: What Runners Get Wrong

September 25, 2026

A male distance runner in athletic gear running along a dirt path through green fields, illustrating how runners need both hydration and electrolytes to sustain endurance training.

By Monica N. for Stacked Fitness Hydration

SEPTEMBER 25, 2026 • 9 MIN READ

Key Takeaways

Sodium is the electrolyte runners lose in the largest quantities through sweat, and research on multi-stage ultramarathons shows plasma sodium can decline steadily over a race even without any symptoms showing up.
Drinking only plain water on long runs can dilute blood sodium and raise the risk of exercise-associated hyponatremia, which the New England Journal of Medicine has linked to real cases among Boston Marathon finishers.
Creatine is not just a strength-training supplement. It also helps muscle cells hold onto water, which is why pairing it with electrolytes supports endurance runners, not only lifters.
Stacked Fitness Hydration's TONE pairs 5g of creatine with 980mg of electrolytes in a single daily stick, built for runners who need more than water alone can give them.

Runners obsess over pace and mileage, but sodium, water, and creatine research tells a different story about what actually gets you through mile eighteen.

The Sweat Rate Myth: Why "Drink to Thirst" Isn't One Size Fits All

Every runner sweats differently, and that single fact is why generic hydration advice keeps failing people who log serious weekly mileage.

Sweat rate depends on your pace, the heat, the humidity, and your own physiology. So two runners on the same course can lose wildly different amounts of fluid and sodium in the same hour.

The foundational American College of Sports Medicine (ACSM) position stand on exercise and fluid replacement established this decades ago. It still shapes how coaches think about hydration today.

That variability is exactly why a single bottle of water rarely covers what a long run actually costs your body. Once you are out past 60 to 90 minutes, especially in heat, the conversation has to include electrolytes, not just fluid volume.

Heat and humidity make the gap even wider. Your body works harder to cool itself, and that cooling happens almost entirely through sweat. A humid summer long run can pull far more sodium out of your system than the same distance on a cool, dry morning, even at an identical pace.

Altitude and fitness level shift the numbers too. That is exactly why "drink eight glasses a day" style advice was never built with runners in mind.

Source: Precision Hydration analysis of over 30,000 individual sweat tests

Sodium Loss During Long Runs: What the Research Actually Shows

Sodium is the electrolyte runners lose in the largest amounts, and newer research shows just how much is genuinely at stake.

A study on a 45-kilometer mountain ultramarathon found measurable electrolyte imbalance and acid-base disturbances in the runners who finished it. That confirms sodium losses during long efforts are real and significant, not a theoretical concern. A separate 2025 study followed female athletes through a seven-stage ultramarathon and found plasma sodium declining steadily across the race, even in runners who never developed symptoms.

That is the part most runners get wrong. You do not need to feel sick for sodium loss to be happening. If you want a fuller picture of what your own sweat is costing you, it helps to know how much sodium you actually lose in a typical workout.

Potassium and magnesium drop too, just in smaller amounts. All three work together to keep muscles firing correctly.

This matters most on back-to-back training days. Sodium you lose on Tuesday's tempo run does not fully replace itself by Wednesday morning if your diet and drinks are not accounting for it.

Runners training for a marathon or ultramarathon are essentially running a slow, ongoing sodium deficit. Correcting for it needs to happen week after week, not just on race day.

The Overhydration Danger Runners Underestimate

Drinking too much plain water during a long run can be just as dangerous as drinking too little.

The classic example comes from the New England Journal of Medicine's study of hyponatremia among Boston Marathon runners. It documented real cases of dangerously low blood sodium among finishers who had been drinking heavily throughout the race.

A 2017 consensus update on exercise-associated hyponatremia confirmed the same pattern. This condition develops when someone drinks more fluid than their kidneys can process, diluting the sodium already in their blood.

This is why some coaches now favor thirst-driven drinking over rigid drinking schedules. A recent narrative review of hydration strategies in ultra-endurance running covers this debate in detail. The safest approach usually combines drinking to thirst with proactively replacing sodium, rather than chasing water volume alone.

Early symptoms of exercise-associated hyponatremia can look a lot like ordinary fatigue: nausea, confusion, and bloating are common warning signs. That overlap is part of what makes it so easy to miss mid-race. Knowing that overhydration is a real risk, not just underhydration, changes how a runner should think about the water station at every mile marker.

Source: Almond et al., Hyponatremia among Runners in the Boston Marathon, New England Journal of Medicine. Most cases were mild.

A man runs along a sunlit forest path, the kind of distance run where electrolyte losses build up gradually.

Why Water Alone Falls Short on Race Day

Plain water rehydrates your total fluid volume, but it does nothing to replace the sodium and potassium your body loses mile after mile.

Electrolytes are what allow muscles to contract, nerves to fire, and fluid to actually stay inside your cells instead of passing straight through you. A 2025 review of sodium intake recommendations for athletes before, during, and after exercise laid this out clearly. Sodium replacement matters for anyone training or racing for more than an hour.

This also explains why so many runners chase cramp prevention in the wrong place. If you have ever wondered why your legs seize up on a hot long run, the research has an answer.

Our deeper look at electrolytes and muscle cramps shows it usually comes down to sodium balance, not stretching or pace. Water gets you halfway there. Electrolytes finish the job.

Electrolytes also speed up how quickly fluid leaves your stomach and reaches the muscles that need it. A well-formulated electrolyte drink can hydrate you faster than plain water during a hard effort, not just more completely. That is a real advantage in the final miles of a long run, when absorption speed matters as much as total volume.

Electrolytes and Creatine: The Stack Endurance Runners Are Missing

Runners fixate on hydration and sodium, but creatine is the piece of the puzzle most endurance athletes overlook entirely.

Creatine is not just a strength-training supplement. It earns its place in a runner's routine for a different reason than it earns one in a lifter's.

It draws water into muscle cells, supporting cellular hydration. It also helps replenish the energy stores your muscles burn through on long runs, which contributes to faster recovery between hard sessions.

That is the exact idea behind stacking creatine with electrolytes instead of treating them as separate categories. Stacked Fitness Hydration built TONE around this principle, combining 5g of creatine with 980mg of electrolytes in one stick. A runner gets sodium replacement and creatine support from a single scoop, rather than juggling two separate products before a long run.

Timing does not need to be complicated either. Most runners do well taking their creatine and electrolyte stack daily, regardless of whether that particular day includes a hard workout. Creatine works by building up in the muscle over time, not by delivering a one-time boost, so consistency matters more than perfect timing around any single run.

Stacked Fitness Hydration

TONE: Creatine + Electrolyte Hydration Mix

Runners lose sodium and other electrolytes every mile. TONE pairs 5g of creatine with 980mg of electrolytes in one stick, so rehydration and recovery support happen together.

Shop TONE

Source: Kreider et al., International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation

Getting It Right: A Practical Electrolyte Strategy for Runners

None of this research has to be complicated once you translate it into a simple plan for your next run.

Start by treating any run past 60 to 90 minutes as an electrolyte event, not just a hydration one. Before you head out, have a plan for sodium during the run, not just water, especially in heat or humidity. Here is a simple runner's checklist worth keeping in mind:

Drink to thirst rather than forcing down water on a rigid schedule
Replace sodium during any effort longer than 60 to 90 minutes, especially in the heat
Pair your electrolyte routine with a daily creatine dose so cellular hydration and recovery are both covered
Pay attention to how you feel late in a run, sluggishness and cramping are often sodium problems, not fitness problems

Young man running alone on a deserted road, illustrating the daily consistency electrolyte and creatine hydration habits require

Between the sweat rate research, the sodium studies, and the hyponatremia data, the throughline is the same: water matters, but it was never meant to work alone. Electrolytes and creatine round out what your body actually needs to perform and recover, run after run.

None of this means hydration has to become a science project before every run. It means treating sodium as seriously as you treat pace, and respecting that overhydration carries its own risks. It also means giving your muscles the creatine and electrolyte support they need to recover between sessions.

Get those three pieces right, and the research suggests everything else, from cramping to fatigue to how you feel on your last mile, tends to fall into place.

For more on this, see Electrolytes 101 and how much sodium you actually lose in a workout.

Frequently asked questions

Do runners really need electrolytes, or is water enough?+

Water covers fluid volume, but it does not replace the sodium and potassium sweat carries away. For runs under an hour in mild conditions, water is usually enough. Past that, especially in heat, electrolyte replacement matters more, which is exactly why TONE pairs electrolytes with creatine in a single daily stick built for active training days.

What is exercise-associated hyponatremia and should I worry about it?+

It is a drop in blood sodium caused by drinking more fluid than your body can process during long exercise, and it has been documented in marathon and ultramarathon runners. It is most common on long, slow efforts where people over-drink plain water. Replacing sodium alongside fluids, rather than water alone, lowers the risk considerably.

Can creatine actually help endurance runners, not just lifters?+

Yes. Creatine draws water into muscle cells, which supports cellular hydration, and it helps replenish the energy your muscles use on long runs. That combination supports recovery between hard training days, not just single-effort strength or power output, which is why more endurance athletes are adding it to their routine.

Why do my legs cramp on long runs even when I drink plenty of water?+

Cramping is usually tied to sodium balance rather than fitness or stretching, according to the research covered in our deeper look at electrolytes and muscle cramps. Drinking water without replacing sodium can dilute what is left in your system, making cramps more likely, not less, on long or hot runs.