Altitude Acclimatisation & Sickness

Unless you have previous experience of trekking,or climbing at altitude; or you have had an opportunity to experience simulated effects of being at high altitude; it is very difficult to know how you are going to react to altitude, or how well you will acclimatise. 

Some people may experience symptoms of altitude sickness from as low as 8,000 feet; however more serious effects would not usually arise until around 12,000 feet. The main consideration is not how high you are going, but how quickly you are gaining altitude.
High altitude is defined in the following three catigories:

  • High Altitude: 5,000 ft – 11,500 ft
  • Very High Altitude: 11,500 ft – 18,000ft
  • Extreme Altitude 18,000 ft+ (Kilimanjaro summit 19,340 ft)

The fact is; young, physically fit males are more likely to suffer from acute mountain sickness (AMS) than any other demographic group. This is largely due to their physical ability to ascend quicker than many other individuals. 

The safest way to ascend to high altitude is by going slowly; the more days you have at altitude and the slower the rate of assent; the greater that chance you have of acclimatising and ultimately reaching the summit. 

If you have had no experience of altitude climbing, or trekking; then you may wish to consider the Kilimanjaro treks lasting 7 days or more; such as the Lemosho route, or Rongai route. To compare the different routes on Kilimanjaro, please see the routes overview page.

Acute Mountain Sickness (AMS)

Acute Mountain Sickness or altitude sickness is very common at high altitude. At over 10,000 feet (3,000 m) approximately 75% of people will suffer mild symptoms of altitude sickness.
Altitude sickness is classified as Mild, Moderate and Severe, with High Altitude Pulmonary Oedema and High Altitude Cerebral Oedema being 2 conditions associated with Severe Acute Mountain Sickness.
Mild Acute Mountain Sickness
The symptoms include:           

  • Headache
  • Nausea & Dizziness
  • Loss of appetite
  • Fatigue
  • Shortness of breath
  • Disturbed sleep
  • General feeling of malaise

Symptoms do not usually prevent normally activity but tend to be worse at night. The symptoms usually disappear within two to four days, ascent can continue at a moderate rate as long as the symptoms remain mild.

Moderate Acute Mountain Sickness

The symptoms include:

  • Severe headache that is not relieved by medication
  • Nausea and vomiting, increasing weakness and fatigue
  • Shortness of breath
  • Decreased co-ordination

Symptoms usually make normal activity, such as walking, difficult. The best test for moderate acute mountain sickness is to get the person to walk in a straight line heel to toe. If a person is unable to walk a straight line it is a clear indication that immediate descent is required.

Severe Acute Mountain Sickness

The symptoms are an increase in the severity of:

  • Shortness of breath at rest
  • Inability to walk
  • Decreasing mental status
  • Fluid build-up in the lungs
  • Severe Acute Mountain Sickness requires immediate descent to a lower altitude.

High Altitude Pulmonary Oedema (HAPO)

Symptoms include:

  • Shortness of breath (at rest)
  • Tightness in the chest, and a persistent cough bringing up white, watery, or frothy fluid
  • Marked fatigue and weakness
  • A feeling of impending suffocation at night
  • Confusion, and irrational behaviour

High Altitude Pulmonary Oedema results from a lack of oxygen resulting in a build up of fluid in the lungs. This fluid prevents effective oxygen exchange and as the condition worsens the level of oxygen in the bloodstream decreases, which leads to cyanosis, impaired cerebral function, and ultimately death. Anyone suffering from symptoms must be evacuated to a medical facility for treatment.

High Altitude Cerebral Oedema (HACO)

Symptoms include:

  • Headache
  • Weakness
  • Disorientation
  • Loss of co-ordination
  • Decreasing levels of consciousness
  • Loss of memory
  • Hallucinations & Psychotic behaviour
  • Coma

High Altitude Cerebral Oedema results from a lack of oxygen resulting in a build up of fluid in brain causing swelling of brain tissue. High Altitude Cerebral Oedema usually occurs after a week or more at high altitude. Severe cases can lead to death if not treated quickly. Anyone suffering from symptoms must be evacuated to a medical facility for treatment.

Altitude sickness medicine (Diamox)

Acetazolamide (diamox) is used for the treatment and prevention of altitude sickness; diamox does not mask the symptoms altitude sickness but actually helps to treat the problem.  Side effects of taking diamox include; tingling of fingers, toes and face. Carbonated drinks tasting flat. Increased urination and occasionally blurred vision.  It would be advisable to take a trial course prior to going to Kilimanjaro as any severe allergic reactions are easier to treat here than at a remote location.

Nutritional Altitude Supplement (ALTI-VIT)

ALTI-VIT is a unique vitamin formula which has been developed to support your bodies requirements at Altitude. Its ingredients include: Siberian Ginseng, Vitamin C, Reishi Mushroom Extract and Ginkgo Biloba, ALTI-VIT is a nutritional altitude supplement to assist with: oxygen uptake, energy production, immune function and sleep quality. ALTI-VIT contains 100% natural ingredients and is available without prescription. More information on the benefits and effects can be found on the ALTI-VIT website.

Analgesics (pain killers)

Ibuprofen/Nurofen is effective at relieving altitude induced headaches.
More information and health advice for Kilimanjaro and the vaccinations you will need for visiting Tanzania can be found on the vaccinations page.


Most of the steps to aid your acclimatisation and reduce the symptoms of altitude sickness will be taken by your guides, but it may be useful for you to know some preventative measures along with a few of the signs and symptoms.

  • On arrival in Moshi, do not overexert yourself, or move higher for the first 24 hours after arriving. We recommend that you take it easy, perhaps by relaxing by the pool.
  • Climb high and sleep low; when possible, sleep at an altitude lower than the highest point you have walked to.
  • If you begin to show symptoms of moderate altitude sickness, don’t go higher until symptoms decrease.
  • If symptoms increase, go down! Always take the advice of your guide as your health and safety is the most important thing to them.
  • Remember that all people acclimatise at different rates. Do not worry if you appear to be the only person in your group suffering, it may just be that it has affected you sooner than other members of your group.
  • Stay properly hydrated; acclimatisation is often accompanied by fluid loss, so you need to drink lots of fluids to remain properly hydrated (at least four to six litres per day). Urine output should be copious and clear to pale yellow.
  • Take it easy and don’t overexert yourself. We cannot emphasise strongly enough the words of the guides “pole, pole” meaning slowly, slowly. It really will increase your chances of getting to summit.
  • Avoid tobacco, alcohol and other depressant drugs including, barbiturates, tranquillisers, sleeping pills and opiates such as dihydrocodeine. These cause a worsening of symptoms.
  • Eat a high calorie diet while at altitude.

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