Hydration Drinks for Marathon Runners: A Buyer's Guide

What 26.2 Miles Does to Your Fluid and Electrolyte Balance

Choosing among hydration drinks for marathon runners starts with understanding what a marathon does to your body. It is hours of continuous sweating, and sweat is not just water. It carries electrolytes, and sodium is first among them.⁶  Over 26.2 miles you lose both fluid volume and the minerals that help your body hold onto that fluid, and the deficit builds quietly across the distance before it may ever register as thirst.

The physiology worth understanding is simple. Sodium is the #1 electrolyte lost during sweat.⁶ Endurance runners lose meaningful fluid and sodium every hour of running, and sweat sodium concentration varies widely between individuals, commonly cited around 1,000 mg (roughly 1 gram) per liter of sweat on average, with high individual variation.⁶ And the cost starts early: being dehydrated as little as 1 to 2% can negatively impact performance, and we often cannot feel 1 to 2% dehydration, so performance may suffer before we understand why.⁷

What you drink on a run has to replace more than water. This guide breaks down how to choose a drink that actually does, and shows how Liquid I.V.®’s HYDRASCIENCE™ fits along the way.

Why Water Alone Falls Short Over Marathon Distances

Plain water replaces fluid volume, but not the electrolytes that drive absorption and retention. On a long run, water alone may not fully replace the fluid and electrolytes lost through sweat. 

For runners, under-replacing electrolytes is a big miss. Water alone replaces fluid but not the electrolytes lost in sweat, and sodium is the electrolyte that helps increase fluid retention and helps distribute water to maintain fluid balance.³ 

Runners might also drink too much plain water. Drinking large volumes without replacing sodium can dilute the body's sodium balance, which is why endurance guidance emphasizes electrolytes alongside fluid.⁷ 

This is where a purpose-built formula earns its place. Liquid I.V. Hydration Multiplier® is clinically proven to hydrate faster than water alone,²,5 and compared to water it delivers longer lasting hydration and better fluid retention.³ The goal on a long run is not just more fluid; it is fluid your body can absorb and hold.

Electrolyte Drink vs Sugary Sports Drink vs Plain Water

Runners typically reach for one of three things. Here is what each does well, and where each can fall short for endurance.

One clarification on sugar: the issue with many full-sugar sports drinks is the volume of sugar relative to the hydration task, not sugar itself. Glucose is a functional ingredient in a true oral rehydration solution, driving glucose-sodium co-transport, the mechanism that pulls water across the gut wall so you hydrate faster.8,9  The right amount, matched to the job, is the point.

A dedicated electrolyte drink pulls ahead on density and evidence. Liquid I.V. Hydration Multiplier delivers 3x the electrolytes of the leading sports drink. The endurance sweet spot is a drink built to replace electrolytes and absorb quickly, with a sugar profile matched to the job.

What to Look For in an Endurance Hydration Drink

This is the heart of the buyer's guide: a decision-factor checklist you can carry into any purchase.

1. Sodium content first. Sodium is the electrolyte you lose most in sweat⁶ and the one that drives fluid retention, so look for a meaningful level, not a trace. For reference, Liquid I.V. Hydration Multiplier provides about 500 mg sodium and 370 mg potassium, roughly 870 mg total electrolytes per serving; the Sugar-Free version provides about 500 mg of sodium and 370 of potassium. (Source: product Nutrition Facts.)

2. A balanced electrolyte profile, not just sodium. Sodium leads, but potassium supports the balance of fluid inside and outside your cells.

3. Fast, clinically backed absorption. Prefer a formula clinically studied as a finished product, not just a list of ingredients. Liquid I.V. Hydration Multiplier is clinically proven to hydrate faster than water alone²,5 and is scientifically formulated for rapid rehydration. 2,⁵

4. Retention, so hydration lasts across the miles. Delivering hydration is not the same as holding it. Liquid I.V. helps the body retain more fluid than water alone  for up to 4 hours*.³

5. A sugar profile matched to the job.  An oral rehydration solution uses glucose functionally rather than as filler. The carbohydrates aid both fluid absorption and help fuel race day efforts. Additionally, any run over an hour long benefits from the fuel an oral rehydration solution provides.7 A sugar-free option can suit shorter daily training or runners managing sugar intake. Liquid I.V. Hydration Multiplier Sugar-Free uses a Patent-Pending Amino Acid Allulose Blend, which functions like glucose and hydrates faster than water alone.¹,2. It’s also Keto-Friendly.⁴ 

6. Format and portability. Single-serve sticks travel with you; a tub and scoop do not. (More below.)

7. A mindful label. Look for no artificial sweeteners or colors and a real nutrient contribution. Liquid I.V. Hydration Multiplier carries 8 vitamins and nutrients with no artificial sweeteners or colors.

A drink that satisfies all seven is a short list. Most cover only two or three.

Before, During, and After: A Marathon Hydration Timeline

According to the American College of Sports Medicine (ACSM), this is a general before, during, and after hydration structure you can adapt to suit your specific needs, sweat rate, and race plan.

Before (the days and hours prior). Arrive hydrated, not scrambling. Steady daily hydration up to 2-4 hours before race-time beats a last-minute chug. Also, feeling thirsty may indicate you are already dehydrated,⁷ so do not use thirst as your only cue. An electrolyte serving including sodium can help retain the consumed fluid.  Liquid I.V. Hydration Multiplier can be used up to 2 sticks per day, so feel free to adapt to your training and pre-race  schedule.* 

During (on the run). Replace fluid and electrolytes at intervals (if available) rather than waiting for thirst. The goal is to prevent excessive dehydration (>2% body weight loss from water) and electrolyte imbalance.7 Sodium is the priority because it is lost most⁶ and drives fluid retention³, however other electrolytes like potassium are also important.7 Match intake to individual conditions such as sweat rate, run duration, intensity, and weather, since hotter and longer runs mean more loss. A possible starting point given by the ACSM suggests drinking 0.4-0.8 Liters per hour and to defer to your own individualized race plan for where you fall in that range.7 

After (recovery). Rehydrate to replace what the race drained (both fluid and electrolytes) so you can bounce back. Liquid I.V. supports rapid rehydration after exercise² and helps the body retain more fluid  for up to 4 hours*.³ Rehydration strategies are strongly determined by how you end the race so think proactively. 

Format and Portability for Long Runs and Race Day

Here is a factor runners underrate: on a long run, the drink you can actually carry is the one that helps. A tub of powder with a scoop does not travel, and consistent dosing matters when you are tired and moving.

Look for convenient, travel-friendly, single-serving sticks that fit a running belt, pocket, or gear bag and mix into a bottle at an aid station without measuring. Liquid I.V. Hydration Multiplier comes in single-serve sticks built for exactly that, it is the #1 powdered hydration brand in America, and it comes in a wide range of refreshing flavors. Taste helps drive intake, and the drink you enjoy is the one you keep reaching for at mile 20.

Compare formats and flavors: explore all hydration options.

Where Liquid I.V. Fits for Marathon Runners

For race day and post-run recovery, Liquid I.V. Hydration Multiplier is the perfect hydration choice. Liquid I.V.'s Hydration Multiplier is a commercial ORS designed to support water absorption and rehydration with a combination of electrolytes and sugar.8,9 . It is clinically proven to hydrate faster than water alone,²,5 delivers 3x the electrolytes of the leading sports drink, and is scientifically formulated for rapid rehydration .2,⁵ Its glucose is functional, driving glucose-sodium together for rapid rehydration, not added as filler.

For sugar-conscious runners, Liquid I.V. Hydration Multiplier Sugar-Free is the everyday option. It is clinically proven to hydrate faster than water alone,² is Keto-Friendly,⁴ and uses the Patent-Pending Amino Acid Allulose Blend. The amino acids do the functional work that sugar used to do. Allulose along with L-glutamine and L-alanine help improve water absorption when paired with electrolytes in the absence of sugar,2 opening an amino-acid co-transport pathway in place of the sodium-glucose one.

Both versions carry 8 vitamins and nutrients with no artificial sweeteners or colors. Find your fit for marathon training on the Liquid I.V. website.

Choosing Your Endurance Hydration Drink

A marathon drains fluid and sodium for hours, and plain water alone does not replace everything  you lose. The runner who wins the hydration decision picks a drink with a beneficial electrolyte profile including sodium and potassium, clinically backed fast absorption 2, retention across the miles 3, and a format they can actually carry.

Keep this in mind: sodium is the #1 electrolyte lost during sweat,⁶ as little as 1 to 2% dehydration can quietly impair performance,⁷ and electrolytes, not water alone, drive absorption and retention.³ Liquid I.V. Hydration Multiplier can help combat with all three of these as an oral rehydration solution, and it is the #1 powdered hydration brand in America.

Frequently Asked Questions

How much sodium do marathon runners lose in sweat? It varies widely by individual.7 Sodium is the electrolyte lost the most in sweat,⁶ which is why runners prioritize replacing it, and losses depend on your sweat rate, the heat, and how long you run among other factors.7 Treat general figures as a starting point and calibrate to your own sweat rate and race plan. 

Is plain water enough for a marathon? Over marathon distances water usually is not enough to replace the fluid and electrolytes lost in sweat. Drinking water with glucose and electrolytes, specifically sodium, are what help your body absorb and hold the fluid you take in.2,3

Electrolyte drink or sports drink for long runs? A dedicated electrolyte drink prioritizes sodium and fast absorption, which is what endurance demands. Many full-sugar sports drinks carry more sugar than the hydration job needs, though sugar itself is not the problem; glucose is a functional ingredient in an oral rehydration solution. The question is whether the sugar volume matches the task.

When should I hydrate before, during, and after a marathon? The American College of Sports Medicine (ACSM) provides general guidelines as a starting point.7 Key takeaways are to arrive hydrated by building steady daily hydration in the lead-up. During the run, replace fluid and electrolytes at intervals rather than waiting for thirst. Afterwards, rehydrate to recover. Defer to your own race plan and practice during training so you’re not thrown off guard on race day. 

Should I use sugar-free or regular hydration for running? Original Hydration Multiplier, which can be considered an oral rehydration solution with glucose as a functional ingredient, suits race day and rapid rehydration.2,8,9, Liquid I.V. Hydration Multiplier Sugar-Free can suit shorter, daily training and sugar-conscious runners. Many runners keep both on hand and match the product to their needs on that day.

Does Liquid I.V. work for marathon training? Liquid I.V. Hydration Multiplier is clinically demonstrated to hydrate faster than water alone,²,5 delivers 3x the electrolytes of the leading sports drink, and supports rapid rehydration after exercise.²,5 That combination of fast absorption, electrolyte composition, and fluid retention is well matched to endurance training.7

Explore Hydration Multiplier to build your training and race-day routine.

References 

1. Bloomer RJ, Pence J, Hellenbrand J, et al. Randomized trial to assess the safety and tolerability of daily intake of an allulose amino acid-based hydration beverage in men and women. Nutrients. 2024;16(11):1766. doi:10.3390/nu16111766

2. Gopalakrishnan ST, Kooima PK, Kavouras IE, et al. Novel allulose amino acid-containing sugar-free beverage results in rapid ad-libitum rehydration following exercise-induced dehydration. Med Sci Sports Exerc. 2025;57:789-790. (Manuscript in preparation.)

3. Bloomer R, Lelko M, et al. Oral rehydration solutions improve measures of hydration over a 4-hour period in healthy men and women. Curr Dev Nutr. 2025;9:106656.

4. U.S. Food and Drug Administration. Guidance for industry: the declaration of allulose and calories from allulose on nutrition and supplement facts labels. https://www.fda.gov/media/123342/download

5. Manuscript in preparation.

6. Baker LB. Sweating rate and sweat sodium concentration in athletes: a review of methodology and intra/interindividual variability. Sports Med. 2017;47(suppl 1):111-128. doi:10.1007/s40279-017-0691-5

7. Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc. 2007;39(2):377-390. doi:10.1249/mss.0b013e31802ca597

8. National Cancer Institute. Definition of oral rehydration solution [Internet]. National Institutes of Health. Published date unknown. Accessed August 20, 2026. https://www.cancer.gov/publications/dictionaries/cancer-drug/def/oral-rehydration-solution-os-1

9. Pérez-Castillo ÍM, Williams JA, López-Chicharro J, Mihic N, Rueda R, Bouzamondo H, Horswill CA. Compositional aspects of beverages designed to promote hydration before, during, and after exercise: concepts revisited. _Nutrients._2024;16(1):17. doi:10.3390/nu16010017.

In-line source note: Nutrition figures (sodium, potassium, calories, vitamins) are cited to product Nutrition Facts / product pages. The "#1 powdered hydration brand in America" and "3x the electrolytes of the leading sports drink" claims are brand/market and clinical-program claims; per the citation rule they are sourced in-line and not folded into the References list above.

*Disclaimer: For educational purposes only. This content is not medical advice. Consult a physician and follow your own race and hydration plan for personal targets.