What electrolytes do you need for running?

Electrolytes are often talked about in running circles, yet they’re also widely misunderstood. Many runners know they “should” be taking electrolytes, especially for long or sweaty sessions, but fewer understand which electrolytes matter, why they matter, and how much is actually helpful. More isn’t always better (as some electrolyte brands lead you to believe), and neither is taking too little.

So what does the research tell us about what electrolytes do, why runners need them, the risks of electrolyte imbalance, and how to think about electrolyte intake in a practical, evidence-informed way, particularly for long-distance running?

What are electrolytes and what do they do?

Electrolytes are minerals that carry an electrical charge when dissolved in fluid. In the human body, they are essential for:

Muscle contraction and relaxation
Nerve signalling
Maintaining fluid balance
Regulating blood pressure
Supporting heart rhythm

The key electrolytes for runners are sodium, potassium, calcium, magnesium, and chloride. Each plays a slightly different role, but they work together as a system meaning balance matters just as much as total intake.

Sodium and chloride help regulate fluid balance and blood volume and are the primary electrolytes lost in sweat.

Potassium supports muscle contraction and nerve transmission and helps counter-balance sodium in cells.

Calcium is required for muscle contraction and bone health.

Magnesium plays a role in muscle relaxation, energy production, and nerve function, and supports calcium regulation.

When electrolyte balance is disrupted, performance and health can suffer.

Why do runners need to take electrolytes?

Running, especially for long durations, leads to electrolyte loss primarily through sweat. While water loss is often the most obvious concern, electrolytes are lost alongside fluids, and replacing water alone can dilute remaining electrolytes in the body leading to health and performance issues, some of which can be serious.

Research shows that prolonged endurance exercise increases electrolyte demands, particularly sodium, due to sweat losses that can range from 300 mg to over 2000 mg of sodium per litre of sweat. However, electrolyte needs can vary considerably from one runner to another, with factors influencing how much electrolytes a runner may need including sweat rate, gender, climate, intensity, body size, and genetics.

Electrolytes are especially important for:

Long-distance running (typically >90 minutes)
Hot or humid conditions
High sweat rates or salty sweaters
Back-to-back training days

Without adequate electrolyte replacement, runners may experience declines in performance, coordination, and recovery.

The risks of not taking enough electrolytes

Failing to replace electrolytes during long or intense runs can lead to a range of issues. These include:

Muscle cramps and weakness

Low sodium, potassium, calcium, or magnesium levels can impair normal muscle contraction and relaxation, increasing the likelihood of cramps and fatigue.

Hyponatremia (low blood sodium)

Drinking large amounts of water without sodium replacement can dilute blood sodium levels. Exercise-associated hyponatremia has been well documented in endurance events and can cause symptoms ranging from nausea and confusion to seizures in severe cases.

Impaired nerve function and coordination

Electrolytes are critical for nerve signalling. Imbalances can affect reaction time, coordination, and perceived exertion.

Reduced endurance and performance

Electrolyte imbalance can disrupt cardiovascular function and increase the overall physiological strain of running, making effort feel harder than it should.

Why taking too much can also be a problem

Just as electrolyte deficiency can be harmful, excessive intake can also create issues. Some commercial products recommend 1000 mg of sodium per hour, which may be appropriate for certain high-sweat individuals, but isn’t appropriate for everyone and can actually be excessive for many runners, causing them issues.

Potential risks of taking excessive electrolytes include:

Gastrointestinal distress
Excess fluid retention or bloating
Increased blood pressure (particularly with chronic high sodium intake)
Disrupted electrolyte ratios, which can impair absorption and function

Research consistently highlights that electrolyte balance, and not maximum intake, is key. Every runner’s sweat composition and physiology is different and so there isn’t a single “perfect” dose for everyone.

How much and which electrolytes should you take?

While individual needs vary, research-informed guidelines can help runners avoid both deficiency and excess. Based on current evidence and practical application, a moderate, balanced approach is often most effective for long runs.

Recommended hourly intake while running

For many runners, an effective but not excessive dosage during prolonged runs is:

Sodium: ~500 mg per hour
Potassium: ~200 mg per hour
Magnesium: ~60 mg per hour
Calcium: ~60 mg per hour
Chloride: ~600mg (included naturally alongside sodium as sodium chloride)

This approach sits below the very high sodium recommendations seen in some products while still providing meaningful replacement for endurance runners.

These amounts can also be easily adjusted based on personal experience, sweat rate, environmental conditions, and gastrointestinal tolerance.

The importance of calcium and magnesium balance

Calcium and magnesium deserve special attention because of their close physiological relationship.

Research indicates that magnesium helps regulate calcium transport and absorption, meaning the two minerals work best when consumed together in balanced amounts. Several studies suggest that a 1:1 ratio of magnesium to calcium supports optimal neuromuscular function, which is why we’ve taken this approach in Sustain.

In fact, taking calcium and magnesium together while avoiding excessive doses of either, may help support muscle function, reduce neuromuscular fatigue, and improve overall electrolyte utilisation.

With evidence linking a 2:1 calcium-to-magnesium ratio with increased markers of inflammation and impaired metabolic function, particularly when magnesium intake is relatively low, it’s important to steer clear of a 2:1 calcium-to-magnesium ratio in electrolyte products.

Individual variability matters

One of the most important takeaways from electrolyte research is that there is no universal formula, even if some brands suggest there is! Factors that influence electrolyte needs include:

Sweat rate and sweat sodium concentration
Body size and sex
Running pace and duration
Climate and altitude
Diet and baseline mineral intake

Some runners may genuinely need more sodium, while others may perform better with lower doses together with balanced potassium, magnesium, and calcium intake.

The goal is to replace enough to support function without overwhelming the system and this is the approach we’ve taken with Sustain.

Choosing the right electrolyte powder for you

Besides the ratio of electrolytes which we have discussed at length, there are a number of other considerations when choosing an electrolyte powder. These include:

Sugar or no sugar? Electrolytes do not require sugar to be effective. While carbohydrate (from sugar) can be useful during long or high-intensity sessions where additional energy is needed, many runners already obtain sufficient fuel from energy gels, chews, or whole-food sources. Adding sugar to electrolytes can increase the risk of gastrointestinal distress, particularly during running, when blood flow to the gut is reduced. For runners who prefer to separate hydration and electrolyte replacement from fuelling, a no-sugar electrolyte allows for more precise control over carbohydrate intake, supports fluid absorption, and reduces the risk of overconsumption. A no-sugar electrolyte is also healthier when taken outside of runs.

Artificial or natural? Electrolyte powders vary widely in their use of artificial colours, flavours, bulking agents and sweeteners. While these ingredients may improve taste, they offer no physiological benefit and can contribute to gut discomfort for some runners, particularly during prolonged exercise. Choosing an electrolyte made with natural ingredients and minimal additives can improve tolerance, reduce the likelihood of nausea or bloating, and make the product easier to consume consistently over time. A simple ingredient list also makes it easier to understand exactly what you’re taking in. Be ingredient list aware however, as some brands claim natural ingredients but when reviewed, the ingredients are unlikely to be sourced from nature. Sustain is probably the most natural and bioavailable electrolyte powder on the market with ingredients of coconut water powder, sea salt, seawater magnesium and marine algae calcium. Its natural ingredients are highly absorbable and sustainable (unlike minerals sourced from rocks).

Flavoured or unflavoured? Whether you choose an electrolyte powder that has a flavour or is unflavoured is simply down to personal choice, although factors influencing your decision include how easily you experience taste fatigue, and your running distance. Ultrarunners, for instance, may opt for unflavoured electrolytes as a particular flavour which may have first been enjoyed, may prove hard to tolerate after many hours of running.

Finding the right balance

Electrolytes are essential for running performance, particularly over longer distances, but more is not always better. Taking too little increases the risk of cramps, fatigue, and hyponatremia, while taking too much can cause gastrointestinal distress, disrupt mineral balance and risk hypernatremia (unusually high sodium levels that can lead to muscle weakness, lethargy, vomiting and worse).

A moderate, balanced intake - around 500 mg sodium per hour alongside potassium, magnesium, calcium, and chloride - is supported by research and may suit many runners. However, individual experimentation, guided by symptoms and performance, is key to finding the perfect electrolyte intake for each runner.

Ultimately, effective electrolyte use isn’t about chasing extremes but is about finding the amount that works for your body, run after run.

Learn more about our Sustain natural electrolyte powder here https://proteinrebel.com/products/sustain-natural-electrolyte

References:

Dai, Q., et al. (2019).
Calcium to magnesium ratio higher than optimal across age groups.
Nutrients, 11(4), 909.
https://pmc.ncbi.nlm.nih.gov/articles/PMC6574898/
→ Demonstrates associations between higher calcium-to-magnesium ratios (≥2:1) and increased inflammation and metabolic risk.
Noakes, T. D., et al. (2019).
Exercise-associated hyponatremia in endurance and ultra-endurance performance.
Medicina, 55(9), 537.
https://doi.org/10.3390/medicina55090537
→ Foundational review on sodium dilution, over-hydration, and electrolyte imbalance in endurance athletes.
Hew-Butler, T., et al. (2017).
Exercise-associated hyponatremia: 2017 update.
Frontiers in Medicine, 4, 21.
https://www.frontiersin.org/articles/10.3389/fmed.2017.00021/full
→ Updated consensus on mechanisms, risk factors, and prevention of hyponatremia.
Shirreffs, S. M., Armstrong, L. E., & Cheuvront, S. N. (2019).
Normative data for sweating rate, sweat sodium concentration, and sweat sodium loss rates.
Journal of Sports Sciences, 37(10), 1115–1123.
→ Quantifies sodium loss variability and supports individualised replacement strategies.
Murphy, G. R., et al. (2019).
Electrolyte composition of sweat during exercise.
PLoS ONE, 14(10), e0223381.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0223381
→ Confirms sodium and chloride as dominant sweat electrolytes, with smaller but measurable potassium, calcium, and magnesium losses.
Baker, L. B. (2017).
Sweat sodium concentration, sweat rate, and fluid replacement needs in athletes.
Sports Medicine, 47(Suppl 1), 111–128.
→ Gold-standard review supporting moderate, tailored sodium replacement.
Costa, R. J. S., et al. (2021).
Systematic review of electrolyte supplementation during endurance exercise.
Applied Sciences, 11(19), 9093.
https://www.mdpi.com/2076-3417/11/19/9093
→ Reviews evidence for sodium and potassium supplementation and cautions against excessive dosing.

Peters, E. M., & Goetzsche, J. M. (2020).
Exercise-associated electrolyte disorders.
Current Opinion in Endocrine and Metabolic Research, 12, 45–50.
→ Clinical overview of electrolyte disturbances in endurance sport.
Zoller, H., & Schaefer, B. (2021).
Magnesium and exercise.
Nutrients, 13(5), 1487.
→ Strong mechanistic support for magnesium’s role in muscle function and energy metabolism.
Volpe, S. L. (2015).
Magnesium in disease prevention and overall health.
Advances in Nutrition, 6(3), 378S–383S.
→ Supports magnesium’s regulatory role in calcium metabolism.