If you have symptoms of mild altitude sickness, you shouldn't go any higher for at least 24 to 48 hours.

Most cases will improve during this time, but it may help if you:

• don't exercise
• drink plenty of fluid (but not alcohol)
• don't smoke
• rest until you feel better

Make sure you tell the people you're travelling with how you feel, even if your symptoms are mild. This will help them be more aware of signs of severe sickness, such as irrational behaviour, if you develop them.

Descending to a lower altitude

If you have mild symptoms of altitude sickness that don't disappear over the course of 24 to 48 hours, the best thing to do is descend by at least 500m (about 1,600 feet).

Don't attempt to climb again until your symptoms have completely disappeared. After two to three days, your body will have acclimatised and your symptoms should disappear.

If you have severe symptoms or your symptoms are getting worse, descend immediately by as much height as possible. This is because severe altitude sickness can be fatal if not treated quickly. Seek immediate medical help when you reach a low altitude.

Oxygen treatment

Increasing your oxygen intake with bottled oxygen or portable hyperbaric chambers (also known as Gamow or Certec bags) can help to temporarily improve some of the symptoms of altitude sickness. 

A portable hyperbaric chamber is a bag you're zipped into, which is then pumped full of air. After one to two hours of treatment, your symptoms should improve significantly. The effect of the treatment is equivalent to descending about 2,000m (6,500 feet).

However, while oxygen treatment or the use of a hyperbaric chamber can relieve the symptoms of altitude sickness, it's not a replacement for descending to a lower altitude. You should always descend if you have severe or worsening symptoms, even if you've had oxygen treatment.

Medication

Painkillers

Painkillers, such as paracetamol or ibuprofen, can be used to treat mild headaches caused by altitude sickness.

Anti-sickness medication

If you're experiencing nausea or vomiting, a type of medication called an anti-emetic may be useful. Promethazine is an anti-emetic medicine often used by people with altitude sickness.

Acetazolamide (Diamox)

Studies have shown that acetazolamide, also available under the brand name Diamox, can help reduce the severity of altitude sickness symptoms, and can also help prevent the condition.

Altitude sickness can change the chemical balance of your blood. Acetazolamide helps correct this chemical imbalance.

However, the drug isn't licensed in the UK for the treatment or prevention of altitude sickness, and it's only available on prescription.

Your GP may consider prescribing acetazolamide if they think it might be helpful, so you should talk to them about the possibility of using it before you travel.

There are a number of common but minor side effects associated with acetazolamide, including numbness or tingling of the face, fingers or toes.

Some people find these quite distressing, so doctors often suggest you try it at home for two days before leaving if you're likely to use it at altitude.

Nifedipine

Nifedipine is often used to treat high blood pressure (hypertension), but it can also be useful in treating high altitude pulmonary oedema. See complications of altitude sickness for more information.

This medication decreases the narrowing of the artery that supplies blood to the lungs, helping to reduce chest tightness and ease breathing. It's usually taken as a tablet at six- to eight-hour intervals. 

Nifedipine can cause a sudden drop in blood pressure, so it's important not to get up too quickly from a lying or sitting position if you take it.