Altitude sickness can turn an exciting mountain trip into a miserable, and sometimes dangerous, experience. The best way to combat it is to ascend slowly, allowing your body time to adapt to thinner air. If symptoms do appear, the only reliable treatment is to stop climbing and descend to a lower elevation.
What Exactly Happens to Your Body at High Altitude?
At higher elevations, the air pressure drops. This means each breath you take contains fewer oxygen molecules. Your body notices this change and starts working harder to keep your organs supplied with oxygen.
Your breathing rate increases. Your heart beats faster. Over days, your kidneys produce more of a hormone that stimulates red blood cell production. These are normal, healthy adaptations. Acute mountain sickness (AMS) happens when your body struggles to adjust quickly enough.
The condition typically begins above 8,000 feet (2,400 meters). Most people can visit this elevation without trouble. Problems usually start when you sleep at that height or go higher.
What Are the First Warning Signs?
Symptoms usually appear 6 to 12 hours after arriving at altitude. The most common early signs are a headache plus at least one other symptom. That other symptom might be fatigue, dizziness, nausea, or trouble sleeping.
Other early signs include:
- Loss of appetite
- Vomiting
- Feeling short of breath with mild activity
- Difficulty falling asleep or waking frequently
A mild headache that fades with rest is common. It does not always mean you have altitude sickness. But a headache combined with other symptoms should be taken seriously. Do not push through these symptoms to reach a summit. That decision can turn a mild illness into a life-threatening emergency.
How To Combat Altitude Sickness With a Smart Ascent Plan
Slow ascent is the single most effective prevention strategy. Research consistently shows that gradual gain in elevation reduces both the frequency and severity of altitude sickness.
The standard guidance is simple. Once you are above 8,000 feet, do not increase your sleeping elevation by more than 1,600 feet (about 500 meters) per day. Every 3,000 to 4,000 feet of gain, take a rest day. On that rest day, sleep at the same elevation both nights.
You can climb higher during the day and return to sleep at a lower elevation. This is often called “climb high, sleep low.” It allows you to see the views and gain fitness while giving your body a lower, easier night.
Ascending too quickly is the main risk factor. If you fly directly to a high-altitude destination like Cusco, Peru (11,200 feet) or Leadville, Colorado (10,200 feet), plan a rest day before any strenuous activity. Your body needs time to catch up.
Does Acetazolamide (Diamox) Help Prevent It?
Yes. Acetazolamide, sold under the brand name Diamox, is a prescription medication proven to prevent and reduce symptoms of altitude sickness. It works by making your blood slightly more acidic, which triggers your brain to breathe faster and deeper. This helps you take in more oxygen at altitude.
Clinical guidelines recommend it for people with a history of altitude sickness and for anyone making rapid ascents above 10,000 feet. It is also useful when terrain forces a faster climb than recommended.
The typical dose is 125 mg taken twice daily, starting one day before ascent and continuing for the first two days at altitude. Doses should only be taken as prescribed by your doctor. Side effects include tingling in the fingers and toes, changes in taste, and increased urination.
Some people take ibuprofen or other anti-inflammatory drugs to prevent altitude headaches. Some studies suggest these may reduce headache risk. However, they do not treat the underlying problem of altitude sickness. They only mask one symptom.
What Is the Only Real Treatment for Symptoms?
If you develop symptoms of altitude sickness, the treatment is descent. Do not wait to see if you feel better. Do not take painkillers and continue climbing.
The rule is simple: if symptoms are mild, stop ascending. Rest at the same elevation and allow your body to acclimatize. If symptoms do not improve within a day, descend at least 1,000 to 2,000 feet.
If symptoms are moderate or severe — severe headache, vomiting, confusion, or difficulty walking — descend immediately. Do not sleep at that elevation. Descend even if it is night or the weather is poor.
Supplemental oxygen and a portable hyperbaric chamber can provide temporary relief. These are useful tools for rescue situations. But they are not a substitute for descent. Symptoms return when the oxygen or pressure is removed.
How Do You Know It Is Becoming Dangerous?
Most cases of altitude sickness are mild and resolve with rest or descent. But two severe forms can develop. Both are medical emergencies.
High altitude cerebral edema (HACE) is fluid buildup in the brain. Symptoms include confusion, drowsiness, loss of coordination, and personality changes. A person with HACE may seem drunk, stagger when walking, or be unable to think clearly.
High altitude pulmonary edema (HAPE) is fluid buildup in the lungs. Symptoms include shortness of breath at rest, a persistent cough, and coughing up pink or frothy sputum. A person with HAPE may feel like they are drowning.
Both conditions can be fatal within hours if untreated. The only effective treatment is immediate descent. Anyone showing confusion, inability to walk in a straight line, or breathlessness at rest needs to go down right away.
These conditions can occur together. They can also occur without obvious warning signs of mild AMS beforehand.
What Makes Some People More Vulnerable?
Your fitness level does not protect you. In fact, highly fit people sometimes push harder and end up in trouble. Age and sex do not strongly predict who gets sick.
The strongest predictor is your personal history. If you have had altitude sickness before, you are more likely to get it again. A previous episode of HACE or HAPE makes future episodes more likely.
Certain medical conditions increase risk. People with heart or lung disease should talk to their doctor before traveling to high elevation. Sleep apnea can worsen at altitude. Pregnancy does not automatically prevent travel to altitude, but it does require a discussion with your obstetrician.
Children can develop altitude sickness too. The same rules of slow ascent apply. Watch children closely for symptoms like fussiness, poor appetite, or vomiting, which they may not be able to describe.
Does Hydration or Diet Make a Difference?
Dehydration is common at altitude because the air is dry and you breathe faster. Drink enough fluids so your urine stays light yellow. But do not overdo it. Drinking excessive water does not prevent altitude sickness.
Avoid alcohol for the first 48 hours at altitude. Alcohol suppresses your breathing and can worsen the effects of low oxygen. It also disrupts sleep, which is already difficult at altitude.
Avoid sleeping pills and sedatives for the same reason. They reduce your breathing rate during sleep, which can lower your blood oxygen further. If you normally take a sleep aid, ask your doctor whether you should continue it at altitude.
Eating regular meals is helpful. Loss of appetite is an early symptom of AMS. If you have no appetite, that is a warning sign, not a reason to skip food.
Can You Train in Advance to Prevent It?
No training program fully prevents altitude sickness. If you live at sea level and fly to 12,000 feet, you will feel the effects regardless of your fitness.
However, being in good cardiovascular shape helps in practical ways. You will be able to hike with less effort, which reduces the strain on your body. Strong leg muscles and good aerobic fitness make the physical work of climbing easier.
Some people try “hypoxic training” using masks or tents that simulate altitude. Evidence on whether this helps prevent AMS is limited. Some studies suggest it may improve performance at altitude, but results are mixed. It is not a reliable substitute for slow ascent.
If you have time, arriving a few days early and doing short day hikes at moderate altitude before your main climb is the most practical preparation.
Frequently Asked Questions
How fast does altitude sickness go away after descending?
Mild symptoms usually improve within hours of descending 1,000 to 2,000 feet. Severe symptoms like confusion or fluid in the lungs require immediate medical care and a larger descent.
Can ibuprofen treat altitude sickness?
Ibuprofen may reduce headache pain but it does not treat the underlying altitude illness. If you have other symptoms like nausea or fatigue, you need rest or descent, not just pain relief.
Is it safe to sleep at high altitude on the first night?
Sleeping at a new high elevation is the most stressful part of acclimatization. It is safer to spend your first night at a lower elevation and climb higher during the day.
Does being physically fit prevent altitude sickness?
No. Fitness does not protect you from altitude sickness. Anyone ascending too quickly can develop symptoms regardless of their exercise level.
