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acute vs. chronic dehydration

Acute Vs. Chronic Dehydration: Causes, Symptoms, Prevention, And Treatment

Acute Vs. Chronic Dehydration Key Points:

  • Dehydration Overview: Affects everyone, causing symptoms from mild to severe, and can be either acute (short-term) or chronic (long-term).
  • Causes and Risk Factors: Includes insufficient fluid intake, high sweat rates, hot climates, and diuretics. Chronic risks include extensive exercise, inadequate water access, and specific conditions like pregnancy.
  • Symptoms: Acute signs include thirst, dry mouth, dizziness, rapid heartbeat, and dark urine. Chronic symptoms add muscle fatigue, dry skin, headaches, and potential kidney issues.
  • Prevention: Drink fluids consistently, especially before, during, and after exercise. Simple tests like urine color checks help monitor hydration.
  • Treatment: Address dehydration by drinking water, electrolytes, and sports drinks. Severe cases may require medical intervention, such as IV fluids.
  • Hydration Strategies: Effective methods include drinking on a schedule or drinking to thirst, and considering environmental and individual factors for optimal hydration.

    Dehydration Doesn't Discriminate

    Dehydration doesn't pick favorites. It can strike anyone—from elite athletes to weekend warriors, to folks who prefer the couch. Symptoms range from mild discomfort to severe, even life-threatening conditions.

    While most people think of dehydration as just being thirsty, it's more like your body drying out like a grape in the sun. But there’s more to it, and knowing other signs can help you prevent it.

    Dehydration comes in two flavors: acute and chronic. Let’s dive into what sets them apart, what to watch for, how to prevent dehydration, and what to do if it happens to you.

    WHAT IS DEHYDRATION?

    According to the American College of Sports Medicine (ACSM), dehydration is simply losing body water. But let’s narrow it down to exercise-induced dehydration since we're talking about athletes here.

    Exercise-induced dehydration occurs when:

    • You lose 2% or more of your body weight from existing water deficits before exercise.
    • You don’t drink enough fluids during exercise to counteract this loss.

    HOW DOES DEHYDRATION AFFECT ATHLETES?

    When athletes lose 2% or more of their body weight through sweat, several unpleasant things can happen:

    • Impaired performance
    • Increased heart rate
    • Reduced blood flow
    • Increased lactate production
    • Electrolyte imbalances
    • Increased skin temperature
    • Heat exhaustion
    • Heatstroke
    • Rhabdomyolysis (muscle damage)
    • Death

    Yes, that last one is serious. Dehydration is like playing a high-stakes poker game with your health.

    ACUTE DEHYDRATION

    Acute dehydration happens quickly, when you lose more fluid than you take in. It’s as simple as:

    Fluid out > Fluid in

    Acute dehydration can mess with your body’s functions and performance, but it’s easy to spot and prevent.

    CAUSES OF ACUTE DEHYDRATION

    • Not drinking enough fluids during the day or exercise.
    • Living in hot and humid climates.
    • Not being acclimated to heat.
    • Taking diuretics.
    • High sweat rate.

    SIGNS & SYMPTOMS OF ACUTE DEHYDRATION

    • Increased thirst
    • Dry mouth and tongue
    • Headache
    • Dizziness
    • Rapid heartbeat and breathing
    • Dry, cool skin
    • Darker urine or less frequent peeing
    • Muscle cramps

    TESTING FOR ACUTE DEHYDRATION

    • Check urine color: Clear or pale yellow means you're hydrated; darker means you need more fluids.
    • Measure urine specific gravity: A medical professional or a refractometer can tell you how concentrated your urine is.

    TREATMENT FOR ACUTE DEHYDRATION

    • Drink fluids: Water, electrolytes, and sports drinks. Avoid caffeine and soda, as they can increase urine output.
    • Cool off: Find shade or go indoors to reduce your body temperature and sweat rate.

    RECOVERY TIME FOR ACUTE DEHYDRATION

    Generally, you can recover in 30-60 minutes once you start drinking enough fluids.

    CHRONIC DEHYDRATION

    Chronic dehydration is long-term and occurs when you consistently don’t drink enough water to replace daily losses from bodily functions, activities, and exercise. Left untreated, it can cause serious health issues needing immediate medical attention.

    CAUSES OF CHRONIC DEHYDRATION

    • Similar to acute causes, plus:
    • Living in hot or humid climates.
    • Spending lots of time exercising or working outdoors.
    • Lack of access to water.
    • Frequent diarrhea or GI distress.
    • Pregnancy and breastfeeding.

    SIGNS & SYMPTOMS OF CHRONIC DEHYDRATION

    • Constant intense thirst
    • Dizziness and confusion
    • Dark-colored urine
    • Extreme muscle fatigue
    • Very dry, flaky skin
    • Persistent headaches
    • High blood pressure
    • Kidney stones
    • Digestive issues like constipation and acid reflux
    • Sunken eyes

    TESTING FOR CHRONIC DEHYDRATION

    • Urinalysis: Tests urine production and concentration.
    • Blood tests: Check electrolyte levels and kidney function.

    TREATMENT FOR CHRONIC DEHYDRATION

    • Drinking water alone often isn’t enough. You might need electrolyte drinks.
    • Follow a drinking schedule to ensure consistent fluid intake.
    • Severe cases might require IV fluids.
    • Reduce alcohol, caffeine, and diuretic medications.

    RECOVERY TIME FOR CHRONIC DEHYDRATION 

    Recovery depends on how long you've been dehydrated and why. Doctors may monitor your hydration over 60 days to ensure you return to normal hydration levels.

    PREVENTING ACUTE AND CHRONIC DEHYDRATION

    The International Society of Sports Nutrition suggests these tips:

    GENERAL HYDRATION GUIDELINES

    • Drink 13-20 ounces of fluid (about one average-sized water bottle) every 2-3 hours.

    BEFORE EXERCISE

    • Drink 16-20 ounces of fluid 2-3 hours before exercise and 6-10 ounces 10-20 minutes before starting.

    DURING EXERCISE

    • Drink 6-10 ounces of fluid every 10-20 minutes.
    • For exercise under an hour, water or electrolyte drinks are fine.
    • For over an hour, use a carb/electrolyte sports drink.

    AFTER EXERCISE

    • Drink 50 ounces of fluid for every kilogram (2.2 lbs) of weight lost.

    STAYING HYDRATED

    There are two main strategies: drinking on a schedule and drinking to thirst. Both have been shown to effectively prevent dehydration.

    DRINKING ON A SCHEDULE

    • Drink at specific intervals during training or racing, e.g., every 10-15 minutes.

    DRINK TO THIRST

    • Drink when you’re thirsty and stop when you’re not. Research shows this is as effective as scheduled drinking.

    DO YOU NEED TO REPLACE ALL FLUIDS LOST?

    Not entirely. It’s difficult to replace every drop of sweat lost during exercise, and that’s okay. Following hydration strategies can prevent performance dips even with some fluid loss.

    FACTORS AFFECTING DEHYDRATION

    • Physical activity: Duration and intensity impact sweat loss.
    • Individual variability: Body weight, genetics, heat acclimation, and metabolic efficiency play roles.
    • Environment: Hot and humid conditions speed up dehydration.
    • Clothing/equipment: Light, breathable, moisture-wicking clothes help.
    • Sweat rate: Some people sweat more and need to drink more fluids.

    CALCULATING FLUID NEEDS

    Use this formula to estimate your hourly sweat rate:

    16 x [(weight before exercise) – (weight after 1-hour exercise)] + [fluids consumed during exercise] = sweat loss in ounces/hour.

    EXERCISING IN HOT WEATHER

    • Exercise early or late in the day.
    • Avoid midday sun.
    • Wear a hat and light-colored clothes.
    • Exercise indoors if it’s too hot outside.

    HYPERHYDRATION AND HYPONATREMIA

    Drinking too much can also be harmful. Hyponatremia occurs when you drink so much water that it dilutes your body's electrolytes, leading to headaches, nausea, confusion, fatigue, and in severe cases, coma, seizures, and death.

    SUPPLEMENTS FOR HYDRATION

    • Electrolytes: Help retain water and maintain blood volume.
    • Creatine: Promotes water uptake in muscles.
    • Betaine: Aids in water retention in cells.
    • Glycerol: Helps cells absorb more water.

    BOTTOM LINE

    Both acute and chronic dehydration can mess up your athletic performance and health. Follow the tips above to stay hydrated and perform at your best.

    About The Author Matt Mosman - Spearfish, South Dakota

    Matt Mosman (MS, CISSN, CSCS) is a research scientist, endurance athlete, and the founder and Chief Science Officer at Simply Good Supplements. Matt holds his B.S. in Exercise Science from Creighton University and his M.S. in Exercise Physiology from the University of California. Matt and his family reside in Spearfish South Dakota where they enjoy running, mountain biking, camping, and all the outdoor adventures Spearfish has to offer.

    References:

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    • Smith-Ryan, A., & Antonio, J. (Eds.). (2013). Sports Nutrition & Performance Enhancing Supplements. Linus Learning.
    • Casa, D. J., Armstrong, L. E., Hillman, S. K., Montain, S. J., Reiff, R. V., Rich, B. S., ... & Stone, J. A. (2000). National Athletic Trainers' Association position statement: fluid replacement for athletes. Journal of athletic training,35(2), 212.
    • Roberts W. FIMS Position Statement. 2012 Fluid replacement for sports safety and performance. International Sportmed Journal, June 2012;13(2):39-42.
    • Goulet, E. D., & Hoffman, M. D. (2019). Impact of Ad Libitum Versus Programmed Drinking on Endurance Performance: A Systematic Review with Meta-Analysis. Sports Medicine, 1-12.