What Causes Altitude Sickness?

Understanding Altitude Sickness

Altitude sickness, also known as acute mountain sickness (AMS), occurs when your body struggles to adjust to lower oxygen levels at high elevations. This condition is most common when ascending to altitudes over 2,500 metres (8,000 feet) too quickly, preventing your body from acclimatising properly.

Key Takeaways

Altitude sickness happens when there's less oxygen.

If you go too high too fast (above 2,500 metres), your body doesn’t have time to adjust, making you feel dizzy, sick, or tired.

You can prevent altitude sickness.

Climb slowly, drink lots of water, eat light meals, and avoid alcohol and smoking to help your body adjust to the altitude.

If you feel unwell, go lower!

The best way to feel better is to descend to a lower altitude. If symptoms get worse, seek medical help immediately.

Why Does Altitude Sickness Happen?

The air becomes thinner as you go higher above sea level, meaning there is less oxygen available with each breath. Your body is accustomed to a certain level of oxygen at lower altitudes, and when you ascend too quickly, it doesn't have enough time to adapt. This oxygen deprivation can cause symptoms such as headaches, nausea, dizziness, and shortness of breath.

Can You Get Altitude Sickness in the UK?

It is highly unlikely to experience altitude sickness in the UK, as the country’s highest mountain, Ben Nevis, stands at just 1,345 metres (4,413 feet). Typically, altitude sickness symptoms begin at elevations above 2,500–3,000 metres (8,000–10,000 feet), meaning you are more likely to encounter it in mountainous regions like the Alps, Andes, Himalayas, or Rockies.

Symptoms of Altitude Sickness

If you ascend to high altitudes too quickly, you may experience a range of symptoms, usually within 6 to 24 hours after reaching an elevation over 2,500 metres. These symptoms include:

• Headache – One of the earliest signs of altitude sickness.

• Nausea and Vomiting – Feeling sick or being physically sick.

• Dizziness or Lightheadedness – A feeling of instability or difficulty maintaining balance.

• Shortness of Breath – Struggling to breathe, even when resting.

• Fatigue – Extreme tiredness and weakness.

• Loss of Appetite – Feeling less hungry than usual.

• Disturbed Sleep – Trouble falling or staying asleep.

In severe cases, altitude sickness can lead to dangerous complications such as high-altitude pulmonary oedema (HAPE) or high-altitude cerebral oedema (HACE), both of which require immediate medical attention.

Risk Factors for Altitude Sickness

Altitude sickness can affect anyone, regardless of age, sex, or fitness level. However, certain factors increase the likelihood of experiencing symptoms:

• Rapid Ascent – Climbing too quickly without allowing time to acclimatise.

• Lack of Acclimatisation – Not giving your body enough time to adjust to higher altitudes.

• Previous Experience – If you have had altitude sickness before, you are more likely to get it again.

• Dehydration – Not drinking enough fluids can make symptoms worse.

• Alcohol or Smoking – Both can affect oxygen levels and worsen symptoms.

• Strenuous Activity – Overexerting yourself at high altitudes increases the risk of developing symptoms.

How to Prevent Altitude Sickness

Prevention is always better than cure. If you are planning a trip to high-altitude locations, follow these steps to reduce your risk:

1. Ascend Gradually

• Where possible, avoid flying directly to high-altitude locations.

• Increase altitude slowly, no more than 500 metres (1,640 feet) per day once above 2,500 metres.

• Take rest days every 3 to 4 days to allow your body to adjust.

2. Stay Hydrated

• Drink plenty of water (3-4 litres per day).

• Avoid alcohol and caffeine, as they can lead to dehydration.

3. Eat a Balanced Diet

• Consume light but high-energy meals, such as carbohydrates, to provide sustained energy.

• Avoid heavy, fatty, or greasy foods, which can be harder to digest at high altitudes.

4. Limit Physical Exertion

• Take it easy in the first 24–48 hours after arriving at high altitude.

• Avoid intense exercise until your body has had time to adjust.

5. Consider Medication

• Acetazolamide (Diamox) is a commonly prescribed medication to help prevent and reduce altitude sickness symptoms.

• Painkillers such as ibuprofen or paracetamol can help relieve headaches.

How to Treat Altitude Sickness

If you develop symptoms of altitude sickness, it is important to act quickly to prevent it from worsening.

1. Descend to a Lower Altitude

• The most effective way to relieve symptoms is to move to a lower elevation as soon as possible.

• A descent of 500–1,000 metres (1,640–3,280 feet) can significantly improve symptoms.

2. Rest and Acclimatise

• Stop ascending for at least 24–48 hours.

• Allow your body time to adjust before continuing your climb.

3. Stay Hydrated and Avoid Alcohol

• Drink plenty of fluids to prevent dehydration.

• Avoid smoking, alcohol, or sleeping pills, as they can worsen symptoms.

4. Use Supplemental Oxygen

• If available, using an oxygen supply can help alleviate severe symptoms.

• Some high-altitude destinations provide oxygen enrichment rooms or portable oxygen tanks.

5. Take Medication

• Acetazolamide (Diamox) can help speed up acclimatisation and ease symptoms.

• Painkillers can relieve headaches and muscle pain.

• Anti-nausea medication can help manage sickness and vomiting.

When to Seek Medical Help

If symptoms worsen or do not improve after 24 hours, it is essential to seek medical assistance immediately. You should descend immediately and seek emergency medical care if you experience:

• Severe breathlessness, even at rest.

• Confusion, difficulty walking, or loss of coordination.

• A persistent, worsening headache that does not improve with painkillers.

• Bluish skin or lips, which indicate a lack of oxygen.

These could be signs of HAPE (fluid in the lungs) or HACE (fluid in the brain), both of which can be fatal without prompt treatment.

Final Thoughts

Altitude sickness can affect anyone travelling to high elevations, but by taking the right precautions, you can significantly lower your risk. The key to preventing altitude sickness is gradual ascent, hydration, proper rest, and awareness of symptoms. If you are planning a trip to high-altitude regions, consider speaking to a healthcare professional about altitude sickness prevention medication, such as Acetazolamide, which is available from UK Meds.