Altitude Sickness: Prevention, Acetazolamide and UK Travel Advice

Altitude sickness, also known as Acute Mountain Sickness (AMS), is a condition caused by ascending to high altitudes (typically above 2,500m or 8,000ft) faster than the body can adjust to the lower levels of oxygen and changes in air pressure. At these elevations, the air is 'thinner', meaning every breath delivers less oxygen to your bloodstream than at sea level.

While anyone can develop altitude sickness regardless of age, sex, or physical fitness, it is most common among those who fly or drive directly to high-altitude destinations, such as base camps in the Himalayas, the Andes, or high-altitude ski resorts. According to NHS guidance, the risk increases significantly at altitudes above 3,000m. Most cases are mild, but if ignored, the condition can progress to life-threatening complications affecting the brain or lungs.

Symptoms of altitude sickness usually develop within 6 to 24 hours of reaching a high altitude. UK travellers often compare the feeling to a severe hangover. It is vital to recognize these signs early to prevent further ascent until symptoms resolve.

Common symptoms include:

• A persistent headache, usually throbbing and felt on both sides of the head.
• Nausea and loss of appetite.
• Dizziness or lightheadedness.
• Fatigue and exhaustion, even while resting.
• Disturbed sleep and shortness of breath during physical exertion.
• Irritability or a general sense of feeling unwell.

If you or your travel companions notice these symptoms, the most important rule is to stop ascending immediately. Continuing to climb while suffering from AMS is the primary cause of severe altitude-related illness.

Prevention is always better than cure when dealing with high-altitude environments. Following NICE clinical knowledge summaries and Royal College of Physicians advice, the gold standard for prevention is acclimatisation.

• Fly-to-High: If flying to a high-altitude city (like Cusco or La Paz), take at least two days of complete rest before attempting any physical activity.
• Climb High, Sleep Low: Try to keep your sleeping elevation lower than the maximum height you reached during the day.
• Gradual Ascent: Once above 3,000m, do not increase your sleeping altitude by more than 300m to 500m per night.
• Rest Days: Schedule a rest day for every 1,000m of ascent.
• Hydration: Drink plenty of water but avoid alcohol, which can worsen dehydration and mask symptoms of AMS.
• Diet: Eat a high-calorie, high-carbohydrate diet to fuel your body’s increased metabolic demands at altitude.

Acetazolamide (commonly known by the brand name Diamox) is a medication that can help prevent and reduce the symptoms of altitude sickness. It is a carbonic anhydrase inhibitor that encourages the kidneys to excrete more bicarbonate. This process acidifies the blood, which stimulates the respiratory system to breathe faster and deeper, thereby increasing oxygen uptake.

In the UK, acetazolamide is not licensed specifically for altitude sickness prevention, but it is widely used 'off-label' in accordance with clinical guidelines for travellers at high risk. It is typically started one to two days before you begin your ascent and continued for at least two days after reaching your maximum altitude.

Note on side effects: Common side effects include a tingling sensation (pins and needles) in the hands, feet, or face, increased urination, and a metallic taste when drinking carbonated beverages. It is a sulfonamide derivative, so it may not be suitable for those with severe sulpha allergies.

While most AMS is manageable, two severe forms require immediate medical intervention. These occur when fluid builds up in the body's vital organs due to extreme pressure changes.

High Altitude Cerebral Oedema (HACE)

HACE involves swelling of the brain. Symptoms include extreme confusion, stumbling (ataxia), hallucinations, and loss of consciousness. This is a life-threatening emergency.

High Altitude Pulmonary Oedema (HAPE)

HAPE involves fluid build-up in the lungs. Symptoms include a cough (sometimes producing frothy spit), cyanosis (blue tint to lips/fingernails), and severe breathlessness even when resting. HAPE can occur independently of AMS or HACE and requires immediate descent and oxygen.

If you are planning a trip to a high-altitude region, consulting an online doctor is a convenient way to ensure you are prepared. A UK-based GP can review your medical history and provide personalised advice or a private prescription for acetazolamide if appropriate.

You should speak to a GP online if:

• You have a pre-existing medical condition, such as heart or lung disease, that may be affected by low oxygen levels.
• You have experienced altitude sickness in the past and wish to discuss preventative medication.
• You are pregnant and planning to travel to high altitudes.
• You need a travel medicine kit tailored to your specific destination.

A consultation via OnlineDoctor24 allows you to discuss these concerns from the comfort of your home, ensuring you have the necessary documentation and medication before you depart the UK.