Many friends plan to travel far to the west or high-altitude areas to experience the journey and unwind. Some of them, having never been to high-altitude regions before, feel uncertain and under great pressure. In past activities, there have also been dangerous incidents caused by a lack of sufficient knowledge about high-altitude acclimatization.



I. What Is High Altitude?

According to internationally accepted altitude classification standards:

1500–3500 meters is considered high altitude. At this height, most people can adapt if given enough time.
3500–5500 meters is considered very high altitude. At this height, individual differences determine whether one can adapt.
Above 5500 meters is considered extremely high altitude. At this height, bodily functions severely decline, and some damage may be irreversible. No one can stay at this altitude for a full year. Even Tibetans and Sherpas generally live below 5500 meters.


From a practical standpoint, people from low-altitude areas generally feel normal with no obvious reactions at altitudes below 2400 meters. Above 2400 meters, with a reasonable altitude progression and enough time, it is still possible to gradually adapt. However, above 5500 meters, no amount of time will allow for full adaptation.



II. What Is Altitude Sickness?

Altitude sickness refers to a series of natural physiological responses that occur when the body adapts to changes such as air pressure differences, lower oxygen levels, and dry air after reaching a certain altitude.

Symptoms of altitude sickness commonly appear after exceeding an altitude of 2700 meters. Arriving rapidly (such as by plane) above 3000 meters makes altitude sickness more likely.

Altitude sickness generally occurs 6–12 hours after reaching high altitude, though in some cases it may appear 1–3 days later. Recovery usually takes 3–7 days, but in severe cases, it may take over two weeks.

Common symptoms of altitude sickness include chest tightness, shortness of breath, dry cough, headache, dizziness, fatigue, loss of appetite, nausea, vomiting, drowsiness, insomnia, and mild fever. Most people will have bluish lips and nail beds due to oxygen deprivation, while others may experience dry skin, chapped lips, or nosebleeds due to the dry air. Severe cases may involve dulled senses, emotional instability, mental agitation, impaired thinking and memory, abnormal hearing, vision, smell, or taste, hallucinations, as well as possible edema, shock, or convulsions.

The symptoms and severity of altitude sickness vary from person to person. Some may only experience one or a few of the above symptoms, while others may have more. Some react sensitively and intensely, while others have milder reactions or almost none. I’ve seen highly sensitive individuals experience mild altitude sickness at just 1700 meters, and I’ve also met people climbing 6000-meter-level snow mountains with very weak altitude reactions. It’s truly remarkable how different people can be.



III. What Factors Affect Altitude Sickness?

Generally speaking, the main factors affecting the severity and incidence of altitude sickness include:


(1) Altitude

The higher the altitude you enter, the stronger the altitude sickness and the greater the probability of various mountain sicknesses. It has been reported that the incidence rate below 3500 meters is 37%–51%, while between 3600 and 5000 meters, it reaches 50%.


(2) Method of Ascent

The speed and extent of ascent into high altitude directly affect the severity of altitude sickness. A rapid increase in altitude leads to stronger reactions than a gradual “step-up” ascent, and the incidence of mountain sickness is higher.

It has been reported that arriving at 4200 meters from sea level within three days results in an 83.5% acute mountain sickness incidence rate, whereas ascending via step acclimatization from 2261 meters and arriving at 4200 meters within 7–15 days results in only a 52.7% incidence rate.


(3) Region and Season

Different regions, even at the same or higher altitudes, may have milder reactions in areas with dense vegetation compared to those with sparse vegetation. Similarly, within the same region, places with good air circulation fare better than those with poor airflow (such as valleys), and daytime conditions are better than nighttime.

In terms of seasons, entering high-altitude areas in winter has a higher incidence rate than other seasons. This is because the cold in winter lowers temperatures and atmospheric pressure, further reducing oxygen levels. Moreover, the cold stimulates metabolism, increasing the body’s oxygen consumption and making respiratory infections more likely.


(4) Individual Constitution

A person’s adaptability to oxygen deprivation mostly depends on innate individual constitution. Factors related to individual constitution include race, place of residence, health status, gender, age, body type, and mental state.

Regarding individual constitution, aside from racial and regional differences, there’s a saying about altitude sickness: “It targets men, not women; the overweight, not the slim; the tall, not the short; the active, not the sedentary.” While not absolute, this has some basis in reality. The reason likely relates to differences in hematocrit levels, oxygen demand, and oxygen consumption among individuals.

An individual’s mental state is also very important. Optimistic people often have milder reactions. Some who don’t understand the high-altitude environment and have heard inappropriate information may experience excessive psychological pressure. At the slightest discomfort, they become nervous or even fearful, which worsens their reaction.

Additionally, those who have had previous high-altitude experience, especially if it was recent, generally experience milder altitude sickness.



IV. Who Should Not Travel to High Altitudes

Before planning to go to high altitudes, you must have a comprehensive and accurate understanding of your own physical condition—don’t be blindly overconfident. Especially for first-time high-altitude travelers, it’s best to undergo a thorough medical check-up and decide whether to proceed based on the results and your doctor’s advice.

Generally speaking, individuals with obvious heart, lung, brain, liver, or kidney diseases, severe anemia, hypertension, retinal diseases, and pregnant women should not enter high-altitude areas.

Those currently suffering from upper respiratory infections with a fever of 38°C or above—or even if below 38°C but with significant respiratory or systemic symptoms—should postpone their trip to high altitudes.

Children are in a critical period of physical development, with relatively weak overall resistance and high sensitivity to the low-oxygen environment of high altitudes. They are more prone to altitude sickness than adults when oxygen-deprived, and the consequences can be more serious and long-lasting. Based on relevant research and experience, it is advised to avoid bringing children under 10 to high altitudes. A safer age is over ten, and I generally follow the standard of around 14 years old.

Elderly individuals who are advanced in age and in poor health are also unsuitable for high-altitude travel. Due to the overall decline in physical functions, weakened immunity, and reduced ability to cope with special environments, they are more susceptible to colds or gastrointestinal issues and are more likely to develop acute altitude sickness.



V. Preparations Before Going to High Altitudes

Before ascending to high altitudes, you should make adequate preparations in the following aspects:


(I) Psychological Preparation

Practice has proven that a strong psychological mindset is a crucial asset in overcoming and conquering altitude sickness. Regarding altitude sickness, you should take a strategic view of it as insignificant but a tactical view of it as important. Don’t let the mere thought of going to high altitudes weigh you down with anxiety, as if you’re heading into battle.

First, you should know that altitude sickness is a normal physiological phenomenon. Most people can adapt to high altitudes and overcome altitude sickness through adjustments. Every year, many people—men, women, young, and old—travel to high altitudes and return safely and smoothly.

Second, don’t overly exaggerate the suffering caused by altitude sickness. The previously mentioned symptoms of altitude sickness do not all occur in one person; everyone’s experience and severity vary, and not everyone will have obvious reactions. If the route and altitude progression are well planned, and the individual has strong adaptability, the symptoms can be minimal or even non-existent. Even if there are some reactions, they are usually within the tolerable range for most people and can be adapted to, alleviated, or disappear with effective measures.


(II) Physical Preparation

Before going to high altitudes, you must ensure your body is in optimal condition.

As previously mentioned, undergoing a medical check-up is essential. If you have any conditions that make high-altitude travel unsuitable, do not push yourself or be blindly overconfident. After all, health and life come first.

If you have minor illnesses, try to treat them as soon as possible before departure.

If your trip to high altitudes involves strenuous activities such as mountaineering or trekking, systematic and advance training is essential. Make sure your physical stamina meets the demands of the activity and has a sufficient surplus.

Many people take preventive health supplements such as inosine, rhodiola, or American ginseng before going to high altitudes to combat hypoxia and boost immunity, which can be somewhat helpful. However, it is not recommended to
take multiple types of these supplements simultaneously.

Based on my personal experience, “inosine oral solution” works faster and more directly against altitude sickness, and it is more affordable. It can generally be taken 2–3 days before departure and continued at high altitudes. Especially when altitude sickness is severe, combining it with “Xinnao Shu oral solution” or “glucose oral solution” yields good relief. It is also one of the commonly prescribed remedies in Tibetan hospitals for altitude sickness. Rhodiola (often labeled as “Nuodikang capsules” in pharmacies), supported by biological and medical experiments and applications, is proven to help combat fatigue and alleviate altitude sickness, but its effects are slower and it is expensive. If using rhodiola, it is generally advised to start taking it at least 7 days before ascending and continue usage.


(III) Knowledge Preparation

Gaining advance knowledge about life, movement, medical care, climate, customs, and other related aspects at high altitudes is very important for any traveler, especially team leaders. Needless to say.

It must be emphasized that before going to high altitudes, thoroughly understanding acclimatization, altitude sickness, and related topics is essential and necessary for both the team and every individual traveler.

(IV) Material Preparation

For high-altitude activities, prepare the appropriate and sufficient materials according to the mode of travel, whether hiking, cycling, or driving.

Whether you are driving or hiking, whether traveling solo or in a group, it is recommended to carry as much basic survival and emergency gear as possible. Leave behind luxury items, indulgent gear, or anything that is non-essential.

On a personal level, focus on preparing your ID, money, basic daily necessities, protective equipment, and essential medications—no need to elaborate further here.

For group activities, if there are many newcomers, it is advisable to bring supplemental oxygen or portable oxygen generators. If reaching very high altitudes with sparse population, it may also be necessary to carry a few doses of “dexamethasone”—provided you know when and how to use it.