Altitude Sickness Prevention: How to Stay Safe When Trekking Abroad

Altitude sickness, also known as Acute Mountain Sickness (AMS), is a collection of symptoms encountered when you travel to elevations above 2,500 metres (approximately 8,000 feet) too quickly. At these heights, the atmospheric pressure decreases, meaning there is less oxygen available in every breath you take.

For British travellers heading to destinations like the Andes, the Himalayas, or Mount Kilimanjaro, understanding how the body adapts to hypoxia (low oxygen) is essential. While most cases remain mild, if the body fails to acclimatise, it can lead to more severe and life-threatening conditions. According to NHS guidance, anyone can be affected by altitude sickness, regardless of age, sex, or physical fitness level. Being an experienced athlete does not protect you from the effects of thinning air.

Symptoms of AMS typically develop within 6 to 24 hours of reaching a high altitude. They are often compared to a severe hangover. It is important to monitor yourself and your trekking partners closely, especially during the first few days of an ascent.

• Headache: Usually throbbing and worsens during the night or upon waking.
• Nausea and vomiting: Loss of appetite is a frequent early indicator.
• Dizziness and lightheadedness: Feeling unsteady on your feet.
• Fatigue: Feeling unusually tired or weak, even with minimal exertion.
• Shortness of breath: Breathlessness that occurs with activity is normal, but breathlessness at rest is concerning.
• Disturbed sleep: Difficulty falling or staying asleep is common at elevation.

Prevention is always better than cure when it comes to travel health. The medical consensus, supported by NICE clinical knowledge summaries, suggests that the speed of your ascent is the single most important factor. Following the 'Golden Rules' of trekking can significantly reduce your risk:

1. Climb High, Sleep Low

Try to spend your days at higher altitudes but return to a lower elevation to sleep. This stimulates the body to produce more red blood cells without putting excessive stress on the system overnight.

2. Gradual Ascent

Once above 3,000 metres, your sleeping elevation should not increase by more than 300 to 500 metres per night. You should also schedule a rest day for every 1,000 metres gained.

3. Hydration and Diet

Drink plenty of paracetamol-safe fluids to counteract the dry mountain air. Aim for a high-carbohydrate diet, as this helps the body use oxygen more efficiently. Crucially, avoid alcohol and smoking, as these can mask symptoms or dehydrate the body further.

For travellers who have a history of altitude sickness or those whose trekking itinerary involves an unavoidably rapid ascent, medication may be recommended. The most common preventative treatment is acetazolamide (sometimes known by the brand name Diamox).

Acetazolamide works by increasing the amount of bicarbonate excreted in the urine, making the blood more acidic. This stimulates the brain to breathe faster and deeper, which improves oxygen intake and speeds up the natural acclimatisation process. It is important to note that acetazolamide is not a 'magic pill' that allows you to fly to the summit; it is an aid to a sensible ascent plan. Common side effects include tingling in the fingers or toes and increased urination. It should be started 1-2 days before you begin your ascent.

If you are planning a trip to a high-altitude region, a consultation with a UK online doctor is a convenient way to prepare. During a digital appointment, your GP can review your medical history, discuss your specific trekking itinerary, and determine if preventative medication is appropriate for you.

Speaking to an online GP allows you to get professional medical advice from the comfort of home, ensuring you have the necessary prescriptions and health knowledge before you head to the airport. They can also provide guidance on other travel essentials, such as vaccinations or malaria prophylaxis, ensuring your travel medicine kit is comprehensive and tailored to your needs. This proactive approach ensures you are not left seeking medical help in remote areas where resources may be limited.

While AMS is uncomfortable, two severe forms of altitude illness require immediate emergency action. These occur when fluid builds up in the lungs or the brain.

High Altitude Pulmonary Oedema (HAPE)

This is fluid in the lungs. Symptoms include extreme breathlessness (even at rest), a persistent cough, and blue-tinted lips or fingernails. It is a medical emergency that requires immediate descent and oxygen.

High Altitude Cerebral Oedema (HACE)

This is swelling of the brain. It is characterised by severe confusion, hallucinations, and 'ataxia'—a loss of coordination where the sufferer staggers as if drunk. Without immediate descent and treatment, HACE can be fatal within hours.