A snowboarder standing on a snowy mountain summit, gazing out over a vast, cloud‑shrouded alpine landscape.

Dehydration and Altitude Sickness: How to Avoid It With Proper Hydration

If your adventures include reaching for the sky on the peaks of Kilimanjaro, K2, or Machu Picchu, you may be familiar with altitude sickness. This common ailment affects many climbers, hikers, and even skiers, sometimes at elevations as low as 8,000 feet. 

In its mildest form, altitude sickness is an unpleasant experience that resolves quickly. However, in severe cases it could cause serious health complications. 

Before your next adventure in the great outdoors this winter, learn more about how to treat altitude sickness, the connection between altitude sickness and hydration, and what you can do to prevent it.

Key Takeaways:

  • High altitude can increase fluid loss through dry air, faster breathing, physical activity, and changes in urination.
  • Dehydration and altitude sickness are different conditions, but they can cause similar symptoms, including headache, dizziness, fatigue, and nausea.
  • Gradual ascent and acclimatization are the primary ways to reduce the risk of severe altitude sickness, but proper hydration can help.
  • Electrolytes can support hydration and replace minerals lost during physical activity.

Travel Hazards at High Elevations

Environments high above sea level carry numerous risks for travelers, including: 

  • Cold temperatures
  • Low humidity
  • Increased ultraviolet radiation
  • Low air pressure
  • Low oxygen.¹ 

The level of hypoxic stress depends on many factors such as the rate of ascent, elevation, and duration of exposure. The human body is highly adaptable to different environments, provided it has the time to adjust properly. Acute acclimatization, or the body's adjustment to environmental changes over a short duration, typically takes three to five days.¹ 

On a climb or hike, this involves stopping for a few days at 8,000 feet before moving on to higher elevations. Taking this time allows proper acclimatization to improve comfort, enhance athletic performance, and mitigate altitude sickness.

Nearly half of all athletes ascending to 8,000-14,000 feet experience headache, malaise, and decreased appetite as a result of altitude sickness.³ It's even possible to get altitude sickness at lower elevations due to different genetic factors. 

Many preexisting medical conditions, such as sickle cell disease, myocardial ischemia, heart failure, obstructive sleep apnea, and any form of hypoxemia, can increase the risk of altitude sickness.¹

Why Does Being at a High Altitude Dehydrate You?

At high altitudes, the air is thinner and contains less oxygen, and it's also much drier. This dry air increases fluid loss through respiration.² Every breath you take at altitude causes you to lose more water than you would at sea level. When combined with exertion, sweat, and more frequent urination, dehydration can become a real risk. Even if you're not sweating excessively, you're still losing water at a higher rate.

Altitude also affects your kidneys. In low-oxygen conditions, the kidneys undergo renal adaptations that increase bicarbonate excretion to help maintain blood pH, which leads to increased urination.⁵ This natural diuretic effect can leave you dehydrated even if you feel like you've been drinking regularly. 

For more information, learn exactly how long altitude sickness lasts.

Can Dehydration Cause Altitude Sickness?

Dehydration and altitude sickness can happen at the same time, but dehydration is not considered a proven cause of acute mountain sickness (AMS). AMS develops in response to exposure to lower oxygen pressure at altitude, with risk influenced strongly by factors such as how quickly you ascend, the elevation reached, and your individual susceptibility.⁶

Types of Altitude Sickness

Altitude sickness is divided into three types.⁴

Acute Mountain Sickness (AMS)

AMS is the most common form of altitude sickness. Its symptoms most closely resemble hangovers, including headache, fatigue, nausea, and vomiting.⁵ The symptoms typically resolve with 24 to 72 hours of acclimatization.

High-Altitude Cerebral Edema (HACE)

If AMS progresses, it can turn into HACE. During HACE, fluid builds up in the brain, which is a potentially fatal condition. The symptoms of HACE consist of: 

  • Headache
  • Dizziness
  • Blurred vision
  • Disorientation
  • Severe nausea
  • Vomiting

In advanced cases, people with HACE can't keep water down or adequately rehydrate. Though rare, HACE can become life-threatening within hours.

High-Altitude Pulmonary Edema (HAPE)

Like HACE, HAPE is a more advanced form of AMS and causes a buildup of fluid in the lungs. It can affect any individual traveling above 8,000 feet, including experienced climbers and athletes. Mild HAPE symptoms can look like a dry cough, but severe symptoms may include shortness of breath at rest, fever, and confusion. HAPE can also be fatal.

General Symptoms of Altitude Sickness

Headache, dizziness, and overwhelming fatigue are hallmark symptoms of altitude sickness. They can strike unexpectedly as your body struggles to adjust.

Symptoms range from mild to severe and typically develop between 6 and 24 hours in a high-altitude environment.⁵ Mimicking the symptoms of dehydration or a hangover, the signs may present as follows:

  • Headache
  • Malaise
  • Dizziness
  • Fatigue
  • Loss of appetite
  • Shortness of breath
  • Symptoms that worsen at night

Diagnosis and Treatment of Altitude Sickness

Both AMS and HACE produce symptoms that mimic other conditions, making diagnosis more challenging. In many cases, the descent is enough to relieve the symptoms of HACE quickly. Oxygen supplementation is used to relieve the headache of AMS, if available.¹ People affected by mild altitude sickness can also stay at their current elevation and treat with medications as an altitude sickness cure.

In the case of HAPE, the symptoms are clearer but may still indicate other conditions like pulmonary embolism, pneumonia, and myocardial infarction. With HAPE, the descent is urgent and necessary to relieve symptoms.

Dehydration and Altitude Sickness: How to Tell the Difference

Dehydration and altitude sickness have overlapping symptoms, so it isn't always possible to tell them apart based on a headache or fatigue alone. In fact, current altitude sickness medical guidelines specifically recommend considering dehydration and electrolyte disorders when evaluating someone who appears to have AMS.⁶

Symptom or sign Dehydration Acute mountain sickness
Headache Can occur Common
Fatigue Can occur Common
Dizziness Can occur Common
Nausea Can occur Common
Thirst or dry mouth More suggestive of dehydration Not required for AMS
Dark or infrequent urine Can suggest inadequate hydration Not a defining feature
Symptoms beginning after ascent May occur if fluid intake is inadequate Characteristic of AMS
Improvement from drinking fluids May improve dehydration-related symptoms Rehydration does not treat AMS itself

A key distinction is that rehydrating treats dehydration, not acute mountain sickness itself.⁶ If symptoms continue or worsen despite adequate hydration, altitude illness should not be dismissed as “just dehydration.”

Dehydration and Altitude Sickness: How Much Water to Drink to Replenish Fluids

As a general rule of thumb, about 4–5 liters of fluid per day may be appropriate during altitude training and physical activity. However, individual needs vary based on exertion, sweat and fluid losses, environmental conditions, and other factors.⁷ During mountain activities, general recommendations suggest approximately 400–800 mL of fluid per hour.

A young man outdoors in a white T‑shirt drinking from a reusable water bottle to rehydrate during exercise.

Preventing Altitude Sickness

Acute Acclimatization

As discussed, acute acclimatization is the best way to prevent altitude sickness. Ideally, give your body two or three days of slow descent or rest to adjust before continuing higher. When driving and flying, it's best to rest for 24 hours at lower altitudes. On foot, plan stopping points at lower elevations and travel no more than 1,000 feet each day, including rest days every 3,000 feet.

Climb High, Sleep Low

"Climb high, sleep low" is an old climber's saying with more than a little truth to it. Altitude sickness is more of a concern when sleeping at elevation. It's important to take day trips for acclimatization, but sleep at lower elevations to get the necessary oxygen. 

If you're experiencing any symptoms of altitude sickness, do not sleep at altitude. Descend immediately so you can sleep at a lower elevation with more substantial air.

Pay Attention to Your Diet

A high-carbohydrate diet is best for adaptation to elevations and lowering the risk of altitude sickness.³ Some people experience a drop in appetite that may lead to protein loss over extended periods of time. 

Iron is also necessary for health and performance at elevation. Iron is a major component of hemoglobin, a type of protein that carries oxygen from the lungs to the cells of the body. Without adequate iron intake, there aren't enough red blood cells to transport oxygen effectively, leading to fatigue. 

Take Ibuprofen

Over-the-counter NSAIDs, including ibuprofen and aspirin, are among the preventative measures used to reduce the effects of altitude sickness on performance.³ Ibuprofen can treat the headaches and pain commonly associated with altitude sickness.

Take It Easy

Regardless of physical condition prior to altitude trips, it's important to take it slow and avoid overexertion. Trying to push your physical limits too much, especially during acclimatization, can increase the risk of altitude sickness, dehydration, and edema. While training and fitness are an important part of trip preparation, some athletes don't have the adaptability or erythropoietin (EPO) levels, a type of cytokine that stimulates red cell production, to adjust to elevation quickly.

How Electrolytes Help With Dehydration and Altitude Sickness

A proper balance of electrolytes and hydration is vital to overall health, especially at high altitudes where dehydration can occur rapidly. Climbing, hiking, skiing, and snowboarding already take a toll on the body, leading to increased sweat and water loss, which needs to be replenished. 

In addition, the body's efforts to adjust to low-oxygen environments at altitude can disrupt the balance of electrolytes and water in the body. Studies show that ascent to altitude is associated with changes in fluid and electrolyte composition in test subjects, many of whom later developed altitude sickness.² Individuals at high altitudes may experience severe salt and water retention, which contributes to altitude sickness.

The best way to tell whether you're taking in enough water is by paying attention to your urine. Ideally, your urine should be light yellow and of adequate volume. If urine output decreases or urine is dark and concentrated, it's important to drink more. Between urination and sweat, your body dumps a lot of electrolytes. To combat electrolyte loss and imbalances, or low sodium levels, take an electrolyte supplement like Buoy to replenish your minerals and nutrients.

Do Electrolytes Prevent Altitude Sickness?

Electrolytes can help support hydration and replace sodium, potassium, and other minerals lost during physical activity. However, dehydration and altitude sickness are different conditions, and electrolyte supplements have not been shown to prevent or treat acute mountain sickness (AMS).⁶ Gradual ascent and proper acclimatization remain the primary strategies for reducing altitude-sickness risk.

Avoid high-sodium foods while taking an electrolyte supplement to ensure that the balance is maintained. You can monitor your electrolyte balance, too. If you’re frequently urinating and it’s clear, that may be a sign you’re overhydrated. Learn what electrolytes are good for and how they can help restore that balance. 

Your Secret Weapon Against Altitude Sickness: Buoy Hydration Drops

With so many variables and risk factors, it's difficult to predict the body's response to high altitudes. Preparation is the best defense, giving your body a chance to adjust to the environmental changes. 

For your next high-altitude adventure, bring some Buoy Hydration Drops along. The portable, squeezable bottle is packed with electrolytes and dissolves completely in your favorite drink for on-the-go electrolytes when you need them. Give Buoy a try today! 

References

¹High-Altitude Travel & Altitude Illness - Chapter 3 - 2020 Yellow Book. https://wwwnc.cdc.gov/travel/yellowbook/2020/noninfectious-health-risks/high-altitude-travel-and-altitude-illness

²Institute of Medicine (US) Committee on Military Nutrition Research. (1996, January 1). Fluid Metabolism at High Altitudes. Nutritional Needs In Cold And In High-Altitude Environments: Applications for Military Personnel in Field Operations. https://www.ncbi.nlm.nih.gov/books/NBK232881/

³Misner, W. (Ph.D.). Sickness at Altitude. Hammer Nutrition Endurance Library. https://www.hammernutrition.com/knowledge/endurance-library/sickness-at-altitude

⁴NHS. Altitude sickness. https://www.nhs.uk/conditions/altitude-sickness/

⁵Taylor, A.T. (2011, January 31). High-Altitude Illnesses: Physiology, Risk Factors, Prevention, and Treatment. Rambam Maimonides Medical Journal, 2(1), e0022. https://pmc.ncbi.nlm.nih.gov/articles/PMC3678789/

⁶ Luks, A. M., Beidleman, B. A., Freer, L., Grissom, C. K., Keyes, L. E., McIntosh, S. E., Rodway, G. W., Schoene, R. B., Zafren, K., & Hackett, P. H. (2024). Wilderness Medical Society Clinical Practice Guidelines for the Prevention, Diagnosis, and Treatment of Acute Altitude Illness: 2024 Update. Wilderness & Environmental Medicine, 35(1 Suppl), 2S–19S. https://doi.org/10.1016/j.wem.2023.05.013

⁷ Karpęcka-Gałka, E., & Frączek, B. (2024). Nutrition, hydration and supplementation considerations for mountaineers in high-altitude conditions: a narrative review. Frontiers in Sports and Active Living, 6, 1435494. https://doi.org/10.3389/fspor.2024.1435494

⁸ Castellani, J. W., Muza, S. R., Cheuvront, S. N., Sils, I. V., Fulco, C. S., Kenefick, R. W., Beidleman, B. A., & Sawka, M. N. (2010). Effect of hypohydration and altitude exposure on aerobic exercise performance and acute mountain sickness. Journal of Applied Physiology, 109(6), 1792–1800. https://doi.org/10.1152/japplphysiol.00517.2010

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