Written by Mo, Foundi CSO, PhD · Updated 11 November 2026
Short answer: For most relaxed 5Ks, no. Water before and after, plus your normal meals, is plenty. The National Athletic Trainers' Association notes that active people eating a balanced diet usually don't need to add anything to their fluids. The picture changes with longer, hotter and sweatier runs, such as a half marathon on a warm day, where some sodium and carbohydrate become worth planning.
This is written for weekend and park runners, not elite racers. Here's the reasoning, and where the line sits.
Why is water enough for most 5Ks?
A 5K is short enough that sweat losses usually stay small, and your meals already supply the minerals. The National Athletic Trainers' Association (NATA) position statement on fluid replacement says that under normal circumstances, physically active people eating a well-balanced diet "should not need to add specific ingredients to their fluids before, during, or after activity". Researchers quoted by the American Heart Association suggest that electrolyte supplementation isn't needed for exercise lasting under about 75 minutes at moderate intensity. For most relaxed runners, a 5K falls well inside that.
What should you drink before and after a 5K?
Start the run having had your usual fluids that day, and drink water afterwards. The American College of Sports Medicine (ACSM) position stand on exercise and fluid replacement describes the aim of pre-exercise drinking as starting the activity normally hydrated. When extra drinking is needed, it suggests doing it several hours before so the body has time to absorb the fluid. In practice, for a morning 5K:
- Drink normally the day before and at breakfast. No need to force litres.
- Bring water if it's hot or if you'll be waiting around at the start.
- Drink water afterwards and eat a normal meal. Food restores the minerals. (See Where most of your electrolytes already come from: food.)
When does a longer run change the answer?
The longer, hotter and sweatier the run, the more sodium and carbohydrate become worth planning for. Sweat varies enormously between people: NATA reports adult sweat rates during exercise from 0.5 to 4.0 litres an hour and sweat sodium concentrations from 10 to 100 mEq/L. ACSM recommends individual fluid plans for that reason, rather than one rule.
| Run | What tends to be enough | Why |
|---|---|---|
| Relaxed 5K, mild weather | Water before and after | Short duration, small losses |
| 5K–10K in summer heat | Water, with attention to drinking enough | Heat raises sweat rate |
| Half marathon or 90+ minutes, especially warm | Fluids plus some sodium, often with carbohydrate | Larger sweat-sodium losses; NATA notes carbohydrate and sodium in the drink can help maintain blood glucose and electrolyte balance |
| Feeling unwell, a health condition, or medication that affects fluids | Ask a pharmacist or doctor | A different question from training routine |
If you're stepping up to a half marathon, practise your drinking plan on long training runs rather than trying something new on race day. Running clubs and race organisers usually publish where water stations are. (More on drink types: Electrolyte mixes, sports drinks and energy drinks.)
How can you tell if you're a heavy or salty sweater?
You can get a rough sense without a lab. Notice whether your shirt is soaked after long runs, or whether white, salty marks dry on your cap or clothes. Both suggest you sit toward the higher end of the range NATA describes. That's useful to know before longer, warmer races. It isn't a reason to change anything for a 5K.
Common questions
Should I drink electrolytes before a 5K? Most relaxed runners don't need to. Your usual fluids and meals are enough. Bring water if it's hot.
Do I need electrolytes after running? After a short run, water and a normal meal usually cover it. After long, hot or very sweaty runs, some sodium with your fluids can make sense.
Do I need electrolytes for a half marathon? Often worth planning for, especially in warm weather or if you sweat heavily. A half marathon takes long enough that sodium and carbohydrate start to matter. Practise your plan in training.
What's the best time to drink electrolytes for running? If you use them, they're most relevant during and after long or hot runs. (See Is there a best time to drink electrolytes?.)
Sources
- McDermott BP et al. National Athletic Trainers' Association Position Statement: Fluid Replacement for the Physically Active. https://www.nata.org/sites/default/files/2025-08/fluid_replacement_for_the_physically_active.pdf. Accessed 9 Nov 2026.
- American College of Sports Medicine; Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. Exercise and fluid replacement (position stand). Med Sci Sports Exerc. 2007;39(2):377–390. https://pubmed.ncbi.nlm.nih.gov/17277604/. Accessed 9 Nov 2026.
- American Heart Association News. Electrolytes can give the body a charge, but try not to overdo it (19 Jun 2024). https://www.heart.org/en/news/2024/06/19/electrolytes-can-give-the-body-a-charge-but-try-not-to-overdo-it. Accessed 9 Nov 2026.
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