Acclimatization Guide on High Altitude

If you want to conquer the adventurous trails of the Himalayas, you need an acclimatization guide for high altitudes. Acclimatization is crucial for a safe high-altitude venture, whether you are a beginner or a seasoned trekker.

High altitude is generally defined as elevations above 2,500 meters (8,200 feet), where reduced oxygen levels can pose significant challenges to the human body. As altitude increases, the air becomes thinner, and air pressure also decreases. If proper precautions are not taken, lower oxygen availability can result in altitude sickness. Acclimatization plays a crucial role in avoiding or minimizing altitude-related risk. It helps your body adapt to high altitudes and changing surroundings. 

During high-altitude treks, such as the Everest Base Camp Trek, Annapurna Circuit Trek, and Annapurna Base Camp, trekkers often experience various symptoms of altitude sickness. These may start as minor symptoms but can quickly progress and become fatal. According to the news by The Himalayan Times, 21 deaths were reported due to altitude sickness by Annapurna Conservation Area in the fiscal year 2080-81 BS. This shows how dangerous high altitudes can be.

To prevent such unfortunate scenarios, every trekker must learn about acclimatization and plan an ideal itinerary depending on their fitness level. In this guide, we will do our best to explain everything related to acclimatization. So, without further ado, let us dive right into our acclimatization guide on high altitude.

Effects of High Altitude on the Human Body

The oxygen level in the atmosphere starts to decrease from 2500 meters (8202 feet). The human body functions best at sea level, where the atmospheric pressure is 101,325 Pa. It gradually decreases as you move to higher altitudes. At 5000 meters, the oxygen in the atmosphere is half of what is at sea level. The human body starts to struggle and cannot function properly. 

When you get to a higher altitude, your body produces more red blood cells to make up for the low oxygen level. Your metabolism also increases, but you will feel less hungry and thirsty. The demanding trails also cause frequent sweating, leading to loss of fluid in the body. As a result, many trekkers suffer from dehydration, which can further expose them to the risk of altitude sickness. Depending on the symptoms, altitude sickness can be categorized into three types: 

Acute Mountain Sickness (AMS)

AMS is the mildest and most common form of altitude sickness. Over 25% of trekkers experience Acute Mountain Sickness after ascending to an altitude above 2500 meters. Symptoms include nausea, headache, fatigue, dizziness, insomnia, shortness of breath, and swelling. Usually, trekkers experience these symptoms within a few hours or days of ascending to a higher altitude. 

High Altitude Pulmonary Edema (HAPE)

Compared to AMS, HAPE is more severe and life-threatening. It is the progressive form of Acute Mountain Sickness. High Altitude Pulmonary Edema occurs when the lack of oxygen in the body leads to fluids accumulating in the brain. Its symptoms include nausea, severe headache, vomiting, disorientation, lack of coordination, dry cough, rapid heartbeat, tightness in the chest, and cyanosis (a blue or purple tinge on lips, nails, or skin). 

The symptoms of HAPE start to develop two to four days after climbing to a high altitude. However, they can also develop earlier, so trekkers must be aware of these symptoms. 

High Altitude Cerebral Edema (HACE)

The most dangerous and severe form of altitude sickness is High Altitude Cerebral Edema (HACE). When the lack of oxygen in the body leads to fluid accumulating in the brain, it causes HACE. Its symptoms are neurological and can even threaten one’s life. HACE’s symptoms include extreme fatigue, severe headache, nausea, vomiting, hallucination, slurred speech, disorientation, blurred vision, psychotic behavior, and loss of coordination. 

The symptoms of HACE can develop in one to three days. Anyone suffering from these symptoms must descend to a lower altitude of at least 1000 meters and seek immediate medical attention. 

Acclimatization Strategies

Acclimatization strategies are crucial for minimizing the risks of altitude sickness and ensuring a smooth adjustment to high-altitude environments. Taking an acclimatization day gives your body adequate time to adapt to the growing atmosphere, changing temperature, and humidity. 

Below, we list some key acclimatization strategies for a safe high-altitude journey. When followed correctly, these strategies can help trekkers, climbers, and high-altitude travelers adapt safely while reducing the risk of severe altitude-related complications.

Ascend gradually

A gradual ascent is the most effective method of minimizing the risk of altitude sickness. Experts recommend ascending to higher altitudes, no more than 300-500 meters per day once above 3,000 meters. This gives your body adequate time to adapt to the changes. Rapid ascents can overwhelm the body, increasing the likelihood of altitude-related illnesses. Similarly, resting every few days is equally important, as it gives the body time to stabilize oxygen levels. Taking acclimatization days enhances respiratory efficiency and adjusts metabolic processes. 

Climb high, sleep low

The “Climb High, Sleep Low” technique is where trekkers ascend to a higher altitude during the day but descend to a lower elevation to sleep. This technique aids in acclimatization by stimulating red blood cell production and oxygen efficiency without overexerting the body. It is a popular strategy for high-altitude trekking acclimatization. 

Stay well-hydrated and eat a nutritious diet

As we mentioned before, trekkers can easily suffer from dehydration during high-altitude journeys. Due to the increased metabolism, trekkers feel less hungry and thirsty. Thus, many trekkers get dehydrated or feel extreme fatigue. As a result, it is important to drink at least 4 to 5 litres of water daily and eat a nutritious diet. You can also drink soups, lemon and ginger teas, and warm fluids. Eat a high-carb and high-protein diet that helps to enegerize your body. Avoid caffeine and alcoholic beverages, as they can disrupt sleep patterns and cause dehydration.

Listen to your body

It is normal to feel tired after a long day of hiking during a high-altitude journey. However, extreme weakness can be dangerous. Do not overexert yourself while ascending to higher altitudes. Pay attention to your body and stay on high alert for symptoms of altitude sickness. If you start feeling unwell, stop and rest. Your body is giving you warning signals. Also, let your trek guide know immediately; they will provide the necessary attention. If the altitude-related sickness symptoms persist or worsen, descend to a lower altitude immediately. 

Take Medication

You can also take medications as an acclimatization strategy. There are medicines like acetazolamide or diamox, nifedipine, dexamethasone, etc., to treat altitude sickness symptoms. Trekkers commonly use Acetazolamide as it aids in speeding acclimatization by improving oxygen absorption in the body. Meanwhile, nifedipine is used for emergency treatment of HAPE, and dexamethasone is used for HACE’s emergency treatment. Before taking any medication, it is important to consult with health professionals. 

Oxygen and Hydration Management

Proper oxygen and hydration management are essential for acclimatization and overall well-being at high altitudes. Staying well-hydrated helps maintain blood circulation, oxygen delivery, and metabolic functions, reducing the risk of altitude sickness. Due to increased respiration and dry air, dehydration is a common issue at high elevations. Therefore, it is recommended that trekkers drink at least 4-5 liters of water daily.

It is crucial to avoid alcohol and excessive caffeine. They can contribute to dehydration and impair the body’s ability to adapt by affecting oxygen absorption and sleep quality. During a high-altitude journey, it is important to monitor oxygen levels regularly. Slow and deep breathing helps maximize oxygen intake. Overexertion will make breathing difficult, so move at a steady pace. 

Supplemental oxygen may be necessary to relieve symptoms in severe cases of altitude sickness, especially in cases of High-Altitude Pulmonary Edema (HAPE) or High-Altitude Cerebral Edema (HACE). It should be used under medical guidance. When symptoms persist despite descent or other treatments, supplemental oxygen is used to stabilize oxygen levels before further medical intervention or evacuation. 

Nutrition and Diet for High-Altitude Acclimatization

Proper nutrition plays a vital role in high-altitude acclimatization, helping the body cope with reduced oxygen levels and increased energy demands. A high-carbohydrate diet is essential as carbohydrates provide a quick and efficient energy source. These foods require less oxygen for metabolism compared to fats and proteins. Consuming iron-rich foods is equally important, as iron supports red blood cell production and enhances oxygen transport in the blood. 

Similarly, foods such as lean meats, beans, spinach, and fortified cereals help prevent anemia, which can worsen altitude sickness. Additionally, vitamin C aids in iron absorption, making citrus fruits, tomatoes, and bell peppers valuable dietary additions. Hydrating foods like soups and fruits help combat dehydration. Meanwhile, supplements like iron, vitamin B12, and antioxidants can further support acclimatization. A well-balanced, nutrient-dense diet ensures sustained energy levels and optimal physiological adaptation to high-altitude conditions.

Physical and Mental Preparation

Physical and mental preparation is essential for successfully adapting to high-altitude environments and minimizing altitude-related health risks. Pre-trip altitude training, such as using hypoxic tents or engaging in high-altitude hikes, helps the body gradually adapt to lower oxygen levels by stimulating red blood cell production and improving oxygen utilization. Strength and endurance exercises, including cardiovascular workouts like running, cycling, and hiking, enhance lung capacity and overall fitness. It makes it easier for trekkers to cope with physical exertion at high elevations.

Additionally, mental resilience plays a crucial role in managing stress and discomfort at high altitudes. Techniques such as mindfulness, controlled breathing, and visualization can help climbers and trekkers stay calm, focused, and adaptable in challenging conditions. Researching the journey and its challenges is essential so trekkers can better prepare for the venture. Proper preparation of both body and mind ensures a safer and more enjoyable high-altitude experience.

Recognizing and Managing Altitude Sickness

Recognizing and managing altitude sickness is crucial for ensuring safety at high elevations. The early warning signs of Acute Mountain Sickness (AMS) include headaches, dizziness, nausea, fatigue, and difficulty sleeping. If left untreated, AMS can progress to more severe conditions like High-Altitude Pulmonary Edema (HAPE), characterized by breathlessness, coughing, and chest tightness, or High-Altitude Cerebral Edema (HACE), which involves confusion, loss of coordination, and altered consciousness. 

The best treatment for altitude sickness is immediate descent to a lower altitude. Symptoms often improve with increased oxygen availability. Medications like Diamox (acetazolamide) can help prevent and alleviate mild AMS by speeding up acclimatization, while oxygen therapy can stabilize oxygen levels in moderate to severe cases. In life-threatening situations, emergency protocols include rapid descent, administration of supplemental oxygen, and the use of a portable hyperbaric chamber to simulate lower altitudes. Recognizing symptoms early and taking prompt action can prevent complications and save lives in high-altitude environments.

Acclimatization Guide for Extreme Altitudes (Above 8,000m)

Acclimatization at extreme altitudes, particularly above 8,000 meters (often referred to as the “Death Zone”), requires special considerations due to the extreme lack of oxygen. In this zone, the oxygen levels are so low that the body cannot fully recover overnight. The oxygen level at this altitude is one-third of sea level, and human life cannot be sustained for a long time. As a result, it can lead to a progressive deterioration in physical performance.

Supplementary oxygen is typically used to maintain adequate oxygen levels in the body and prevent severe altitude sickness. High-altitude camps are strategically set up to allow climbers to gradually acclimatize, with periods of ascent to higher camps followed by descents to lower ones to rest and adjust. In these extreme conditions, climbers typically follow a “climb high, sleep low” strategy, ensuring they don’t push too hard without allowing the body to adapt. 

Many climbers do rotation climbs to get their bodies used to the high altitude. They will ascend to higher camps and return to lower camps a few times. Likewise, many 8000-meter expedition teams spend weeks at base camps situated at 4500 to 6000 meters. They also climb training peaks of 5000 to 6000 meters to train their bodies. It aids climbers in pre-acclimatization, and their bodies can function well in low oxygen. Acclimatization to extreme altitude ensures your survival and safety in the infamous death zones of the mountains. 

Conclusion

Successful high-altitude trekking or climbing requires a combination of key acclimatization techniques. These techniques help the body adjust to lower oxygen levels and reduce the risk of altitude sickness. Gradual ascent, following the recommended 300-500 meters per day, is critical, along with utilizing the “climb high, sleep low” approach to stimulate acclimatization while minimizing strain. Staying well-hydrated, maintaining a high-carb diet, and consuming iron-rich foods enhance energy efficiency and oxygen transport. 

Pre-trip physical conditioning, both in terms of endurance and mental resilience, is equally vital for managing the physical and psychological demands of high-altitude environments. We hope you find our acclimatization guide on high altitudes helpful. Good luck with your high-altitude venture, and make sure you follow these strategies for a safe and memorable journey!