How to Hydrate Before, During, and After Your Workout

Hydration has had a moment.

From multi-coloured jumbo Stanley cups to Yeti and Owala bottles (affectionately dubbed "emotional support bottles"), the way we carry our water became a whole personality.  Then came #WaterTok, and even a Liquid IV storyline in the beloved Off Campus series. Hydration officially crossed over into pop culture.

But here's what all that hype doesn't tell you: how much to actually drink, when to drink it, and whether plain water is even enough.

Spoiler: Sometimes it may not be. That's where the real questions begin.

Whether you're training for your first 10K, building up to a triathlon, or deep in HYROX prep, the core takeaway is this: hydration is one of the highest-leverage things you can get right before race day. As a registered sports dietitian, I've watched solid race performances unravel because of something as fixable as this. So let's break it down before, during, and after.

Before Exercise: Start Ahead, Not Behind

Here's the thing about hydration: by the time you're thirsty, you're already playing catch-up.

Your goal going into any workout or race is to show up already well-hydrated. That doesn't mean chugging a litre of water right before you start. It just means not showing up dehydrated in the first place.

What to aim for:

• In the 2–4 hours before exercise, drink about 5–7 mL of fluid per kilogram of body weight. For a 65 kg person, that's roughly 325–650 mL (about 1–2 standard water bottles). ¹
• About 15–30 minutes before you start, top up with another 150–250 mL if you feel like you need it. ¹
• Pale yellow urine (think lemonade, not apple juice) is your green light. ²

Pro tip: On race morning, coffee counts. A regular coffee contributes to your fluid intake, and for most people, the mild diuretic effect is negligible at habitual intake levels. No need to skip your ritual. ³

During Exercise: Match Your Sweat Rate (Roughly)

You don’t need fancy equipment for this. Just weigh yourself before and after your workout, without clothes, to get a good idea of your sweat rate. For every kilogram you lose, that’s about one litre of fluid.¹ Try to keep your test under 2 to 3 hours, since longer workouts can throw off the calculation.

Some dehydration during exercise is normal. The goal is to avoid losses greater than 2-3% of body weight, which is where performance starts to take a hit. Elite athletes in endurance events may exceed this threshold simply because their fluid needs outpace what's realistic to consume at race pace.

General hydration guidelines based on how long you exercise:

• Under 45–60 minutes: Plain water is enough. You don’t need electrolytes or carbs.⁴
• 60–90+ minutes: This is where electrolytes, especially sodium, start to earn their place. Sodium helps your body keep fluid, which helps prevent the drop in performance that comes with dehydration. Worth noting: Sodium isn't a performance booster in the traditional sense; it's more of a performance protector.⁵
• Longer efforts or hot/humid conditions: You'll want fluid, electrolytes, and, depending on intensity, carbohydrates too.¹
• Cold or high altitude: You might need more fluids than expected. Heavy clothing increases sweat losses in the cold, and dry air at altitude means you lose more water just breathing. If you're new to high altitude, pay extra attention as your body adjusts.

A good place to start is to drink 400 to 800 mL of fluid per hour during moderate exercise. Drink more if it’s hot or if you sweat a lot. It’s better to sip regularly than to drink a lot all at once at aid stations.¹

This is where a well-planned fuelling kit makes a real difference. Having your hydration tabs, gels, or drink mix already portioned means you can execute your plan without scrambling on course.

After Exercise: Rebuild, Don't Just Rehydrate

Recovery hydration is less about drinking a specific amount in the moment and more about giving your body what it needs to actually recover.

The basics:

• Aim to replace 125–150% of fluid losses over the 2–4 hours after exercise. If you lost 1 kg of body weight, drink approximately 1.25-1.5 L of fluid. ¹
• Include sodium through salty foods, an electrolyte drink, or both. Sodium helps you retain the fluid you're drinking rather than flushing it straight through. ⁶
• Pair your fluids with a carb-and-protein recovery snack or meal within 30–60 minutes of finishing. Hydration and recovery nutrition work together. ⁷ This strategy is crucial if you compete or train multiple times in the same day (for example, think soccer tournaments, track meets, or morning and evening triathlon training sessions). 8

What counts as fluid? Pretty much anything that's liquid at room temperature: water, milk, smoothies, broth, sports drinks, even fruit. You don't need to rely solely on plain water after your workout. ¹

A Quick Cheat Sheet

The Bottom Line

Staying hydrated is simple, but it takes some planning. The athletes who succeed on race day aren’t always the fastest or most naturally gifted. They’re the ones who come prepared and stick to their plan. This is just as true for nutrition and hydration as it is for pacing.

If you’re unsure how to begin, our curated fuelling kits are here to help. Each kit has everything you need, already portioned and ready, so you can focus on your race when the day comes.

This post was researched and drafted with Claude (Anthropic) and edited for accuracy by Ashley Leone, Registered Sports Dietitian and founder of Fuel Kit. 

Disclaimer: This post is intended for general educational purposes. Individual hydration needs vary. If you have a specific health condition or are unsure about your needs, consult a registered dietitian or healthcare provider.

References

 

1. Thomas DT, Erdman KA, Burke LM. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. Journal of the Academy of Nutrition and Dietetics. 2016;116(3):501–528. https://doi.org/10.1016/j.jand.2015.12.006
2. Kostelnik, S. B., Davy, K. P., Hedrick, V. E., Thomas, D. T., & Davy, B. M. (2021). The Validity of Urine Color as a Hydration Biomarker within the General Adult Population and Athletes: A Systematic Review. Journal of the American College of Nutrition. 2021;40(2), 172–179. https://doi.org/10.1080/07315724.2020.1750073
3. Killer SC, Blannin AK, Jeukendrup AE. No evidence of dehydration with moderate daily coffee intake: a counterbalanced cross-over study in a free-living population. PLOS ONE. 2014;9(1):e84154. https://doi.org/10.1371/journal.pone.0084154
4. Sawka MN, Burke LM, Eichner ER, et al. American College of Sports Medicine position stand: Exercise and fluid replacement. Medicine & Science in Sports & Exercise. 2007;39(2):377–390. https://doi.org/10.1249/mss.0b013e31802ca597
5. Hew-Butler T, Loi V, Pani A, Rosner MH. Exercise-associated hyponatremia: 2017 update. Frontiers in Medicine. 2017;4:21. https://doi.org/10.3389/fmed.2017.00021
6. Shirreffs SM, Maughan RJ. Volume repletion after exercise-induced volume depletion in humans: replacement of water and sodium losses. American Journal of Physiology. 1998;274(5):F868–F875. https://doi.org/10.1152/ajprenal.1998.274.5.F868
7. Margolis LM, Allen JT, Hatch-McChesney A, Pasiakos SM. Coingestion of Carbohydrate and Protein on Muscle Glycogen Synthesis after Exercise: A Meta-analysis. Med Sci Sports Exerc. 2021 Feb 1;53(2):384-393. doi: 10.1249/MSS.0000000000002476. PMID: 32826640; PMCID: PMC7803445.
   
8. Naderi A, Rothschild JA, Santos HO, Hamidvand A, Koozehchian MS, Ghazzagh A, Berjisian E, Podlogar T. Nutritional Strategies to Improve Post-exercise Recovery and Subsequent Exercise Performance: A Narrative Review. Sports Med. 2025 Jul;55(7):1559-1577. doi: 10.1007/s40279-025-02213-6. Epub 2025 Apr 12. PMID: 40221559; PMCID: PMC12297025.