Should You Use Energy Drinks Before or During Workouts?

Attractive young black woman on sportswear and with braided hairstyle drinks water next to a car before she starts her training. She's outdoors next to a park in the daytime in a summer morning.

Jimena Roquero / Stocksy

The use of high-caffeine energy drinks before and during exercise has become increasingly popular, but energy drinks don't always mix well with exercise. While the caffeine and taurine they deliver might improve performance in endurance exercise, these drinks can't replace sports drinks that provide energy and electrolytes. Dietitian Dee Rollins, PhD, warns that energy drinks can lead to dehydration if you don't ensure you're getting enough fluids.

Sports Drinks vs. Energy Drinks

Traditional sports drinks such as Gatorade and Powerade include water, sodium, sugars, and sometimes potassium in proportions that help the body absorb fluids and salts lost in sweat and breath while exercising. The sugars not only help the body take in the water, but also provide fuel for muscles that need sugars to keep performing well during long walks, runs, or bike rides.

A small amount of salt helps protect the body from hyponatremia (also known as water intoxication), which can happen if you drink a large amount of water without any salt.

Energy drinks, on the other hand, are formulated to deliver caffeine and other stimulants, such as guarana or ginseng, to give a rush of energy. They may also contain taurine, an amino acid that may boost performance during exercise by helping muscular contraction and the removal of waste products.

But energy drinks are not designed to replace lost fluids during exercise. Some products come in small cans that deliver a large amount of caffeine in a small amount of fluid. Many are carbonated, which can lead exercisers to experience burping, nausea, and a bloated feeling.

Marketing at Athletic Events

The energy drink Red Bull is often handed out at running and walking events by marketers, which might lead people to think that it is a sports drink. "Most people assume that if you stick something in their hand while they are exercising, that it is good for them," says Rollins.

But Red Bull comes in small cans that pack as much caffeine as a cup of coffee (80 milligrams) and more than a can of cola (40 milligrams). Caffeine is a mild diuretic that can cause a frequent urge to urinate in the short term, if you're not experienced with caffeine.

Dangers of Too Much Caffeine and Exercise

Rollins notes that if you have already had a cup or two of coffee in the morning, adding a can of energy drink can put you over the amount of caffeine most dietitians think is a reasonable limit for the day.

Studies show that having the right amount of caffeine onboard may improve performance for endurance exercises such as running and for muscle strength and endurance. According to a review of 34 studies, it appears caffeine plays a role in improving performance. But it must be taken in moderate doses, about 5 mg to 6 mg per kilogram of body weight.

The International Society of Sports Nutrition recommends 3 mg/kg to 9 mg/kg of caffeine. The U.S. Food and Drug Administration reports toxic effects at 1200 mg.

If exercisers rely on energy drinks, they may drink two to three small cans, thinking they haven't had enough fluids. If they drink a larger can, it may contain two servings. Many pain medications, sinus medications, and other beverages also contain caffeine.

"People may be in more trouble than they realize," said Rollins. She says a general consensus is that 250 milligrams per day of caffeine should be the limit. Drinking more than 400 milligrams a day—two cups of coffee and an energy drink—can lead to jitters, nausea, or even heart palpitations.

Effects of Caffeine When Exercising

Caffeine is a mild diuretic, which can stimulate an urge to urinate. This removes water from the body, especially if you are not accustomed to caffeine. However, this doesn't affect overall hydration.

Caffeine can also have a laxative effect. "When you walk or run, you make your whole GI tract move, from mouth to rectum," noted Rollins. This can lead to needing a restroom more often, or with more urgency (runner's trots).

Preventing Dehydration

There is no magic formula for determining how much water and sports drink you need to prevent dehydration while exercising. Everyone reacts a little differently. The recommendation from the American College of Sports Medicine (ACSM) for walkers and runners is to pre-hydrate (i.e., being sure you are adequately hydrated before you even start exercising), and then drink during and after exercise to replace water lost through sweat.

Contrary to what many people believe, thirst is not a reliable indicator of dehydration, especially during exercise.

Don't ignore hunger pangs; some people will feel hungry rather than thirsty when they're dehydrated.

Weighing yourself before and after a workout can tell you whether you are hydrating correctly. You should neither gain nor lose weight over the course of a single workout. If you lose weight, you are dehydrated. A 2% or greater weight loss is when your performance begins being compromised. A 4% or greater weight loss can lead to illness. If you gain weight, you are drinking too much and may put yourself at risk of hyponatremia.

Recommendations for Endurance Exercise

The American College of Sports Medicine (ACSM) offers tips to help ensure proper hydration during endurance exercise. Staying properly hydrated before, during, and after exercise is imperative to optimize athletic performance and safety.

Here are some general guidelines recommended by the ACSM:

  • Before exercise: Make an effort to start hydrating several hours prior to your planned activity. Aim to 5 to 6 milliliters of fluid intake per kilogram of body weight.
  • During exercise: If you're exercising for more than 60 minutes, or in warm weather, select a fluid replacement beverage (sports drink) that contains sodium (20 to 30 meq/L), potassium (2 to 5 meq/L), and carbohydrate (5% to 10%) for maximum hydration.
  • After exercise: Consume similar sports beverages or drink water and eat foods that contain some sodium for proper rehydration. For each kilogram of body weight lost during exercise, slowly consume 1.5 liters of fluid.

Water is generally considered the best form of hydration. However, for endurance exercise, sports drinks can be more effective at getting your body to absorb fluid quickly. Unlike sports drinks, energy drinks are not considered a proper source of hydration, especially in regards to endurance activities when hydration is paramount.

9 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Southward K, Rutherfurd-Markwick KJ, Ali A. The effect of acute caffeine ingestion on endurance performance: A systematic review and meta-analysis. Sports Med. 2018;48(8):1913-1928. doi:10.1007/s40279-018-0939-8

  2. Cleveland Clinic. Hyponatremia.

  3. Higgins JP, Babu K, Deuster PA, Shearer J. Energy drinks: A contemporary issues paper. Curr Sports Med Rep. 2018;17(2):65-72. doi: 10.1249/JSR.0000000000000454

  4. Souza DB, Coso JD, Casonatto J, Polito MD. Acute effects of caffeine-containing energy drinks on physical performance: A systematic review and meta-analysis. Eur J Nutr. 2017;56(1):13-27. doi:10.1007/s00394-016-1331-9

  5. Goldstein ER, Ziegenfuss T, Kalman D, et al. International Society of Sports Nutrition position stand: Caffeine and performanceJ Int Soc Sports Nutr. 2010;7(1):5. doi:10.1186/1550-2783-7-5

  6. U.S. Food and Drug Administration. Spilling the beans: How much caffeine is too much?

  7. Killer SC, Blannin AK, Jeukendrup AE. No evidence of dehydration with moderate daily coffee intake: A counterbalanced cross-over study in a free-living populationPLoS ONE. 2014;9(1):e84154. doi:10.1371/journal.pone.0084154

  8. Kenefick RW. Drinking strategies: Planned drinking versus drinking to thirst. Sports Med. 2018;48(Suppl 1):31-37. doi:10.1007/s40279-017-0844-6

  9. Amin S, Liguori G. FACSM principles of hydration. ACSM's Health & Fitness Journal. 2019;23(2):5-7. doi:10.1249/FIT.0000000000000459

By Wendy Bumgardner
Wendy Bumgardner is a freelance writer covering walking and other health and fitness topics and has competed in more than 1,000 walking events.