Learn About Preventing Altitude Sickness When Traveling High

Understanding Altitude Sickness: What Happens to Your Body at High Elevations

Altitude sickness, also called acute mountain sickness (AMS), occurs when your body doesn't have enough oxygen at high elevations. As you climb higher, the air becomes thinner, meaning there are fewer oxygen molecules in each breath you take. At sea level, the air contains about 21% oxygen. At 8,000 feet above sea level, that same 21% is spread across a larger space, so each breath delivers less oxygen to your lungs and bloodstream.

Free Career Quiz Guide for Job Seekers →

Your body normally maintains a careful balance of oxygen and carbon dioxide. When oxygen levels drop, your body goes into compensation mode. Your heart beats faster to pump more blood. Your breathing becomes deeper and more frequent. Your body also produces more red blood cells to carry oxygen more efficiently. These changes take time—usually 1 to 3 days—which is why altitude sickness typically appears after arrival at high elevation, not immediately.

The risk of altitude sickness increases significantly above 8,000 feet. According to medical research, about 25% of people traveling to 8,000 feet experience some symptoms of AMS. At 12,000 feet, roughly 50% of visitors report symptoms. At 14,500 feet and higher, the percentage climbs even more steeply. However, altitude sickness is not a sign of weakness or poor fitness—even athletes can develop symptoms, while some sedentary people may not.

Symptoms typically include headache, fatigue, nausea, dizziness, and shortness of breath. Some people also report difficulty sleeping, loss of appetite, or a general feeling of malaise. Mild symptoms often resolve within 24 to 48 hours as your body acclimates. However, symptoms can worsen into more serious conditions like high altitude cerebral edema (HACE) or high altitude pulmonary edema (HAPE), both of which require immediate medical attention and descent to lower elevation.

Practical Takeaway: Understanding that altitude sickness results from your body's struggle to get enough oxygen helps explain why prevention strategies focus on giving your body time to adjust. Recognizing that this condition affects many people—regardless of fitness level—removes shame from the experience and encourages people to take preventive measures seriously.

Gradual Ascent: The Most Effective Prevention Strategy

The single most reliable way to prevent altitude sickness is ascending gradually. This allows your body time to acclimatize—to produce more red blood cells, adjust breathing patterns, and stabilize fluid levels in your tissues. Studies show that people who ascend slowly experience altitude sickness at significantly lower rates than rapid ascenders.

Free Guide to Diarrhea Causes and Home Remedies →

The general guideline for safe ascent is to gain no more than 1,000 to 1,500 feet per day above 8,000 feet elevation. Some mountaineers use the saying "climb high, sleep low," meaning you can hike to a higher elevation during the day but should sleep at a lower elevation to allow your body to recover overnight. This strategy lets you experience higher altitudes while giving your body the nighttime hours to adjust.

For trekking in mountain regions, many outfitters and guide services build in acclimatization days. For example, a trek to Machu Picchu in Peru at 7,970 feet might include 2 to 3 days in Cusco at 11,150 feet before hiking higher. A trek to Everest Base Camp in Nepal at 17,598 feet typically spans 12 to 14 days, with scheduled rest days built in. These rest days aren't wasted time—they're essential for your body's adaptation process.

If your travel plans require reaching high elevation quickly (such as flying directly to Denver at 5,280 feet or to Bogotá at 8,660 feet), you can still reduce altitude sickness risk by limiting strenuous activity on your first day and taking additional time for acclimatization before engaging in intense exercise or climbing even higher.

Practical Takeaway: When planning mountain travel, build in extra days for gradual ascent rather than rushing to your final destination. If you must arrive at high elevation quickly due to flight schedules, plan lighter activities for the first 24 to 48 hours and avoid strenuous exertion until your body has begun adapting.

Hydration and Nutrition: Supporting Your Body's Adjustment

Proper hydration is critical at high altitude because your body loses water more rapidly than at sea level. The air at high elevations contains less moisture, and you breathe faster and deeper when adjusting to altitude, both of which increase water loss through respiration. Additionally, some medications used to prevent altitude sickness increase urination, further depleting your body's fluid stores. Dehydration worsens altitude sickness symptoms and slows acclimatization.

Get Your Free Denver Apartment Rental Guide →

The recommendation is to drink 3 to 4 liters of water daily when at high altitude, more if you're very active. A practical way to monitor hydration is checking your urine color—pale yellow indicates good hydration, while dark yellow suggests you need more fluids. At high altitude, you may not feel as thirsty as you normally would, so you need to drink deliberately and regularly rather than waiting for thirst signals.

Nutrition also matters significantly. Your body burns more calories at altitude as it works harder to process oxygen and maintain body temperature. Eating regular meals and snacks provides the energy your body needs for acclimatization. Carbohydrates are particularly important—they require less oxygen to metabolize than fats or proteins. Many mountaineers eat frequent, small, carbohydrate-rich meals rather than large meals spaced far apart.

Avoid alcohol at high altitude. Alcohol increases urination, leading to dehydration, and it can mask symptoms of altitude sickness, delaying recognition of a serious problem. Similarly, limiting caffeine on your first days at altitude may help, though some people find that avoiding caffeine altogether worsens headaches caused by altitude adjustment.

Practical Takeaway: Pack a water bottle and drink consistently throughout each day at high altitude. Bring shelf-stable snacks like nuts, dried fruit, energy bars, and crackers. Plan to eat something every 2 to 3 hours rather than waiting for scheduled meals. These simple practices provide your body the fluids and calories it needs to acclimatize successfully.

Medications and Supplements: Options to Consider with Medical Guidance

Several medications can reduce altitude sickness risk or severity. Acetazolamide, commonly known by the brand name Diamox, is the most widely studied and used preventive medication. It works by altering the body's chemistry to reduce fluid accumulation in tissues and improve breathing patterns. Studies show acetazolamide reduces the risk of altitude sickness by approximately 50% when taken before and during ascent. A typical preventive dose is 125 milligrams twice daily, starting one day before ascent and continuing for two to three days at high elevation.

Free Guide to AARP Flight Discount Options and Air Travel Savings →

Dexamethasone, a corticosteroid, is another medication shown to prevent and treat altitude sickness. It works through a different mechanism than acetazolamide and may be preferred for people who cannot tolerate acetazolamide's side effects. Common side effects of acetazolamide include tingling in fingers, toes, and lips, altered taste (especially carbonated beverages), and increased urination. These side effects are generally mild and temporary but can be bothersome for some travelers.

Ibuprofen, a common over-the-counter pain reliever, has shown modest benefit in reducing headache associated with altitude sickness. Some research suggests it may reduce overall AMS symptoms slightly when taken before and during ascent, though it's not as effective as acetazolamide.

Ginkgo biloba is a herbal supplement that some travelers use, though scientific evidence for its effectiveness is mixed. Studies show conflicting results, with some suggesting modest benefit and others showing no significant advantage over placebo. If you choose to use supplements, inform your doctor, as some may interact with other medications.

Any medication consideration should involve conversation with your healthcare provider. Your doctor can assess your personal health situation, discuss potential side effects, and determine whether preventive medication makes sense for your planned travel. Medications are most beneficial for people traveling to very high altitudes quickly or those with a history of altitude sickness.

Practical Takeaway: Schedule a pre-travel visit