Altitude Sickness

Altitude Sickness

Altitude Sickness can affect people who climb or travel to a high altitude, particularly if they ascend too quickly.

  • Symptoms usually develop between 6 to 24 hours after reaching altitudes more than 3,000m
  • Treatment available to reduce severity of symptoms

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Altitude sickness occurs when you are receiving an insufficient amount of oxygen from the air at high altitudes. Situations in which this typically happens include driving, hiking, mountain climbing, and any other form of activity which takes place at a high altitude. people who are not used to high altitudes are affected the most.

The symptoms can appear both immediately or gradually. Some of them include:

  • Fatigue
  • Nausea
  • Insomnia
  • Abrupt vomiting
  • Sudden headache
  • Shortness of breath
  • Faster than usual heart rate
  • Increased breathing rate
  • Change in the breathing pattern (at night)
  • Frequent urination

Mild altitude sickness is a very common condition. there is no scientific evidence which can determine who is and who isn’t most likely to get it. Factors such as a person’s sexuality and/or fitness level play no role in whether or not you’ll develop altitude sickness. This condition can be very dangerous and should not be taken lightly. It is imperative that you take proficient hiking or camping gear if you plan to trek in high-altitude climates.

In order to compensate for the lower oxygen levels, a person will have to breathe faster and their heart will have to beat more regularly. Despite the increased rate of breathing and the increase in blood oxygen levels, they will never return to sea level concentrations.

Altitude sickness can affect you in three main ways. You may develop one or more of these.

  • High-altitude pulmonary oedema
  • Acute mountain sickness
  • High-altitude cerebral oedema


The main cause of altitude sickness is when a person ascends too rapidly and outpaces their body’s ability to adjust to the depleting levels of oxygen. As the altitude begins to increase, the air will become thinner. Altitude sickness will most commonly be developed at elevations above the height of 8000 feet and when the rate of ascension is faster than 1000 feet per day. It is estimated that around 20% of all hikers, skiers, and those travelling to high altitude elevations between 8000 and 18000 feet, will experience altitude sickness. Those who travel any higher than 18000 feet will risk this statistic increasing to as much as 50%.

The process when a human body gradually adjusts to the decreasing levels of oxygen is named as acclimatisation. On an average, it will take the human body 1-3 days to fully adapt to the new change in altitude. Those who do not leave enough time to acclimatise before continuing to venture upwards will have the highest risk of falling ill.

Your risk of getting affected by altitude sickness becomes higher when:

  • The altitude at which you sleep is higher
  • The altitude to which you climb is higher
  • You climb too quickly
  • You already have altitude sickness
  • It runs in the family (this might be a reason)
  • You are more active

Types Of Treatment

The best possible way of treating altitude sickness is to quickly descend to a lower altitude; anywhere from 1500-3000 feet lower than the altitude you were it should be effective. Failing this, and if your symptoms are only relatively mild, you can simply delay ascending any further and allow for some time for your body to adjust. You should seek medical attention if the severity of your symptoms is advanced.

If you decide to stay put at the altitude you’re at, you must ensure that you rest and take it easy. Limit any walking or general activity, make sure you drink plenty of water and do not continue to ascend until all your symptoms have passed. As mentioned, this process can take anywhere from 1-3 days to happen.

If you believe you require some treatment in the form of an effective medicine, we can prescribe acetazolamide (Diamox) which speeds up the acclimatisation process significantly. This, in turn, will relieve any negative symptoms and improve your restricted breathing ability. For very mild symptoms, basic over-the-counter painkillers, such as ibuprofen, can work proficiently.

There are ways to prevent altitude sickness.

  • Climb to higher altitudes slowly (this allows your body to adjust according to the low oxygen levels)
  • Do not drive directly to high altitudes (take breaks in between)
  • Do not overexert yourself
  • Try to sleep at lower altitude

Treating Acute Mountain Sickness

If you develop the symptoms of acute mountain sickness, stop moving forward and rest at the same altitude. Symptoms tend to improve on their own within 24-48 hours. However, there are medicines if you feel uncomfortable for a longer period of time. Ibuprofen or a paracetamol can be taken for a headache which is one of the most common symptoms.

The most common medicine for acute mountain sickness is acetazolamide. It helps speed up your acclimatisation. However, it has to be prescribed by your doctor. The usual dose is - 125 mg two times a day.

Treating High-Altitude Cerebral Oedema

High-altitude cerebral oedema develops in a person who already had acute mountain sickness. In this case, the conditions worsen and start to interfere with the function of the brain. High-altitude cerebral oedema is a severe condition. If you suffer from this, descend to a lower altitude immediately. This condition can be fatal. Treatments include external oxygen supply and a steroid medicine (dexamethasone). These relieve symptoms and you will be able to descend to a lower altitude.

Treating High-Altitude Pulmonary Oedema

The reason how and why high-altitude pulmonary oedema develops is not known. Some of the small blood vessels of the lungs can show a rise in pressure due to high altitude. This leads to a leakage from the blood vessels. Hence, fluid escapes from them into the lungs. This is when high-altitude pulmonary oedema occurs. Immediately descending down from the high altitude is a must.

Treatments include external oxygen supply and nifedipine medicine. These relieve symptoms and you will be able to descend to a lower altitude.

If you are looking for some expert help, book an ONLINE consultation with our GMC Registered Clinicians at

Patient discretion and confidentiality top the priority list at!

Questions & Answers

Climbing too quickly at a high altitude can be dangerous. Why?

When we climb to high altitudes, the oxygen and air pressure levels drop. Our body needs time to adjust to these changes. We respond to such changes by breathing faster. This increases our heart rate resulting in a boost of the blood oxygen levels. This will not return to normal. If a person does not give himself time to adjust to the dropping levels of oxygen, altitude sickness develops. At times the symptoms can be very serious and he will have to descend to a lower altitude immediately.

How can this sickness be prevented?

The best method for preventing altitude sickness is through acclimatisation. This is the process of allowing your body enough time to adapt to a new oxygen concentration at a higher altitude. Put simply, it means to ascend at a slow and steady pace.

How can I self-diagnose altitude sickness?

If you develop a headache as well as at least one other symptom within 24-48 hours of changing altitude level, you should strongly consider it being altitude sickness. If you have never developed this condition before, you may be unsure if your diagnosis is correct. A large number of experienced climbers will be able to recognise the symptoms in others who are starting to develop this condition.

Are there any after-effects of altitude sickness?

The majority of cases will be of people who have only developed a mild form of altitude sickness. In such cases, symptoms will decrease as a person returns to a lower altitude and there will be no lasting adverse effects. However, if a person was to develop a severe case of altitude sickness and as a result suffered from swelling and fluid in the brain/lungs, they could be at risk of further serious complications, including a coma or even death.

If you are looking for some expert help, book an ONLINE consultation with our GMC Registered Clinicians at

Patient discretion and confidentiality top the priority list at!

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