What Is Acute Mountain Sickness? Its Causes, Symptoms, And Prevention Tips

February 6, 2025

Mountain Sickness & Acclimatization, Trekking & Hiking Tips

Today, I will explain Acute Mountain Sickness(AMS). A most common high-altitude illness that can be treated with appropriate knowledge and preventive practices. In this article, I will share information about the types of AMS, symptoms, causes, and share some life-saving tips to avoid them.

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Understanding Altitude Sickness

In layman’s terms, altitude sickness is a condition in which your body struggles to keep up with the high-altitude environment of 8,000 feet (2400 meters). Due to the low pressure at higher elevations, the air becomes thinner. The lack of sufficient air reduces the oxygen level in your blood, often leading to symptoms like headaches, dizziness, shortness of breath, fatigue, and nausea.

Mountain sickness commonly occurs when trekkers ascend too quickly without allowing their bodies enough time to acclimatize properly. If left untreated, it can get worse and may lead to severe forms of altitude sickness like HAPE & HACE.

But don’t worry, most of the AMS cases can be easily avoided with, treatment, resting, and gradually adjusting to the altitude can help manage the symptoms. With that keeping in mind, let’s discuss types of altitude sickness:

What Is Acute Mountain Sickness (AMS)?

Starting with Acute Mountain Sickness or AMS is an initial condition of altitude sickness. It can happen to anyone even if you are physically fit for the trek. We have seen that 3-5 out of 20 trekkers in every group experience AMS which is quite common and can be easily handled with proper guidance.

Why Does AMS Happen?

As you trek higher in the mountains above 8,000 feet, the air becomes thinner, meaning there is less oxygen available. Your body needs time to adapt to this change, and if it doesn’t get enough time, AMS can set in.

One of the most common reasons for developing Acute Mountain Sickness is ignoring early symptoms. Many trekkers, even experienced ones, dismiss the initial signs of altitude sickness and continue trekking, which can worsen their condition, often leading to HAPE or HACE. I’ll be discussing these serious complications in the following sections.

Who Is At Risk Of Getting AMS?

The AMS is not about how much you can run or lift weight, instead it’s about how well your body can adjust itself to low oxygen levels. However, factors like rapid ascent, lack of acclimatization, and dehydration.

How To Identify The Symptoms Of AMS?

AMS symptoms typically develop within a few hours of reaching high altitude, though some trekkers may begin experiencing them early in their ascent. On the other hand, some individuals may not feel the effects until they start descending from the summit. To help you identify AMS, here’s a list of key symptoms to watch out for:

Headache
Nausea or vomiting
Dizziness or lightheadedness
Fatigue and weakness
Shortness of breath
Loss of appetite
Trouble in sleeping
Tiredness

Headache is considered the main sign of Acute Mountain Sickness(AMS), and it is accompanied by nausea, dizziness, and shortness of breath very quickly. However, in some cases, trekkers have developed AMS without experiencing a headache. If you notice any of these symptoms, it is crucial to take immediate action and begin your recovery measures to prevent further complications.

How To Prevent Acute Mountain Sickness?

Be Vigilant About The Symptoms: Always look for signs of headache, bad stomach feeling, or loss of appetite.

Alert Your Guide/Friends: If you experience any of these symptoms, inform the people around you. It’s best to tell your guide and begin the curative course Diamox and you should be able to recover in one hour. In case, signs of AMS persist then it’s better to descend at a safer altitude.

Carry a Pulse Oximeter: It’s highly recommended to bring a reliable pulse oximeter to regularly monitor your blood oxygen levels while trekking at high altitudes. A reading of 85 is generally considered safe, but if it drops below this threshold, it’s a clear sign to take preventive measures against Acute Mountain Sickness (AMS) before symptoms worsen. Most importantly, always listen to your body. If you are gasping for air and experiencing dizziness, then it’s time to seek help.

What Is High Altitude Pulmonary Edema (HAPE)?

HAPE (High-Altitude Pulmonary Edema) is a severe condition of AMS (Acute Mountain Sickness) that typically develops when trekkers ignore early symptoms. As HAPE progresses, fluid builds up in the lungs, reducing oxygen absorption, and it can feel like trying to breathe underwater.

This is a critical high-altitude emergency that requires immediate attention from a trained trekking guide, proper high-altitude sickness treatment, and possibly evacuation to a lower altitude for stabilization.

Trekking at high altitudes requires vigilance and ignoring the earlier signs of AMS can lead to dangerous conditions like HAPE. However, incorporating safety measures and altitude acclimatization tips can help prevent these life-threatening conditions, ensuring a safer and more enjoyable trek.

Who Is At Risk Of Getting HAPE?

Only a few trekkers can develop HAPE! Trekkers who have ignored their AMS and continued to climb up without medications are more prone to HAPE. But if you are continuously in check with your symptoms of AMS then you can not have HAPE.

What Are The Symptoms Of HAPE?

So, the question is, how can you recognize the warning signs of high-altitude pulmonary edema?

Here’s a list of key symptoms to watch for:

Fatigue
Breathlessness
Dry Cough
Blue Nails & Lips
Heave Movements
Rattling Sounds From The Chest

Trekkers with HAPE show the common signs of laborious movements, fatigue, gasping for breath, and dry cough. However, in severe cases of HAPE, you will notice blue nails and lips. Also, you can hear gurgling noises with each breath. If you experience any of these symptoms or you have noticed someone, coughing and gasping a lot for even while sitting.

Then it’s time to take curative medicine and descend back to the base camp. As you walk downhill you will feel better but do not stop unless you have descended to at least 8,000 feet.

Essential Steps to Take If You Experience HAPE Signs

Here are the essential precautionary measures to follow when you notice HAPE signs during your high-altitude trek:

Inform your guide Or friends/fellow trekkers
Start a curative course under your guide’s instruction
Descend and lose as much altitude as possible in the next 3-4 hours
Keep your symptoms in check while descending

What Is High Altitude Cerebral Edema (HACE)?

HACE is brain-related high-altitude mountain sickness in which a trekker’s brain starts to swell. This happens due to the dilation of blood vessels in your brain. It typically occurs at altitudes above 12,000 feet (3,600 meters) causing persistent headache, dizziness, pukey feeling, loss of appetite, etc.

Who Is At Risk Of Developing HACE?

While the risk of developing High Altitude Cerebral Edema (HACE) is rare, it remains a serious and life-threatening condition for high-altitude trekkers. This extreme mountain illness may not affect most adventurers, but understanding its causes, symptoms, and prevention is crucial for safe high-altitude trekking. Being informed can help you recognize early warning signs and take necessary precautions during your Himalayan trekking expedition.

HACE Symptoms: Early Signs & Warning Signals

Here is a list of warning signs you should monitor closely:

Dizziness and difficulty in navigating
Queasy feeling
Headache which remains persistent after medications
Forgetting things
Difficulty in completing daily tasks
Irrational talking

High Altitude Safety Prevent And Manage HACE

The chances of developing HACE are rare, but knowing these life-saving tips can make all the difference:

Keep monitoring your symptoms
Inform your guide Or friends/fellow trekkers
Start curative course under guide’s instruction
Descend down and lose as much altitude as possible in the next 3-4 hours
Do not stop until you reach 8,000 ft

Conclusion

I hope this article will be a helpful guide for trekkers navigating high-altitude challenges. I highly recommend checking out this article in which I have explained how you can treat AMS, HAPE, & HACE. And make sure to share it with your fellow trekkers. Explore with courage, trek with caution, and enjoy the journey of your dream trek.

Mountain Sickness & Acclimatization