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What you need to know about Kilimanjaro Altitude Sickness?

The majority of climber fails to reach the summit of Kilimanjaro, the Uhuru Peak 5895m, not due to the lack of fitness but Altitude Sickness. Kilimanjaro climb has a unique set of challenges, the most dangerous being altitude sickness. A significant proportion of people who climb over 2800 m above sea level develop some symptoms relating to altitude.

Altitude sickness, also called Acute Mountain Sickness (AMS), hypobaropathy and soroche, is an illness caused by low air pressure, especially low partial pressure of oxygen, which many climbers experience at high altitudes.

AMS is caused by exerting yourself at high altitudes, especially if you have not been properly acclimatized. It is most common at altitudes above 2800 meters, and Kilimanjaro’s peak is nearly 6000 meters above sea level. At this height, the air pressure (and the amount of oxygen it contains) is less than half that at sea level and has been comparable to ‘working with only one lung’.

AMS can be serious, especially as it can be debilitating, and it generally occurs far from places where you can easily administer medical treatment.

Of course, not everyone suffers from AMS, and it is very difficult to predict who is or is not vulnerable to it. Generally speaking, a fit person is less vulnerable than an unfit person because their cardiovascular system can operate at low pressures longer without as much strain. Anyone can be susceptible at altitudes above 3500 meters, no matter their fitness level if they have not spent some time getting used to the low atmospheric pressures first.

Undoubtedly the best way to see how you will react to high altitude is to go high and try to do some exercises.

Kilimanjaro  Altitude Sickness  

Kilimanjaro has become a very popular trek as it’s a way for ordinary hikers to experience a high mountain summit with no technical skill. Being what’s known as a “walk-up”, without the need for ropes and climbing gear, some people underestimate the potential for serious, life-threatening situations due to the altitude.

Kilimanjaro’s summit falls into the “extreme altitude” category, along with Aconcagua and Denali (Mt McKinley). Everest and K2 are “ultra” altitude, where acclimatization is impossible.

A Brief Introduction to Kilimanjaro Altitude Sickness 

  • At the summit of Kilimanjaro, there is approximately 49% less oxygen than at sea level. However, it’s not the percentage of oxygen in the air that changes; it’s the lower barometric pressure (air pressure) of the atmosphere.
  • The percentage of oxygen in the air is the same, 20.9%, but its availability is reduced by reducing air pressure. What this means, in simple terms, is that for any volume of air you breathe in, there are fewer molecules of oxygen available.
  • The reduced air pressure has other problems associated with it, allowing fluid to collect outside of the cells, around the brain (High Altitude Cerebral Edema) and the lungs (High Altitude Pulmonary Edema), both very serious conditions.

Altitude Sickness: What is it?

Mountain sickness has three main forms: Acute Mountain Sickness (AMS), High Altitude Cerebral Edema (HACE) and High Altitude Pulmonary Edema (HAPE). Additionally, AMS can be mild (very common and manageable with the right treatment), moderate, and severe (immediate descent necessary).

Let’s take a closer look at these conditions.

Acute Mountain Sickness (AMS)

According to Dr Peter Hackett of the Institute for Altitude Medicine, AMS can affect anyone above 6,000ft. The initial sign is usually a headache, which confusingly can also be a sign of dehydration or over-exertion. If other symptoms develop, then a diagnosis of AMS is probable.

Mild AMS

  • In its mildest form, the symptoms can resemble a hangover, with nausea, headache, fatigue, and a loss of appetite. If you experience these symptoms, it’s important to tell your guide and not simply try to push through. You can often resolve mild symptoms with rest and adequate hydration.

Moderate AMS

  • Suppose the symptoms of mild AMS start to get worse. In that case, a headache that you can’t shift, dizziness, coughing, shortness of breath, nausea and vomiting indicates that you are not adapting to the altitude (acclimatizing). It would be best to descend to the last elevation that you felt “well”.
  • Treatments such as ibuprofen for headaches or anti-emetics for nausea can mask worsening symptoms and should not be relied upon for continued ascent.

Severe AMS

  • If a person suffering from moderate AMS ignores the symptoms pushing through to a higher elevation, there’s a risk that the condition can become severe. Severe AMS can lead to life-threatening complications (HAPE and HACE), and immediate descent is mandatory.

Symptoms can include:

  • Severe headache.
  • Ataxia (lack of coordination, inability to walk properly, staggering).
  • Increased coughing and shortness of breath.

Someone with severe AMS will likely need evacuation from the mountain either by stretcher or helicopter.

Complications resulting from severe mountain sickness are HAPE and HACE.

High Altitude Pulmonary Edema (HAPE)

HAPE can develop due to the lung arteries originating excessive pressure due to the low oxygen environment. This pressure causes the build-up of fluid around the lungs.

Confusingly, a climber can develop HAPE even if they don’t seem to have symptoms of severe AMS.

Look out for:

  • Coughing up blood or mucus
  • Abnormal lung sounds
  • Extreme listlessness
  • Difficulty breathing
  • Lips going blue
  • Confusion, lack of coordination

Anyone at altitude who feels as though they have a respiratory infection should assume it’s HAPE until a medical professional proves it to be otherwise. If HAPE is suspected, oxygen is often administered in conjunction with immediate evacuation to a medical facility.

As oxygen levels in the blood drop, the brain can suffer from a lack of oxygen, leading to HACE.

High Altitude Cerebral Edema (HACE)

HACE is a very dangerous condition that requires immediate medical treatment. As the fluid builds up around the brain, the climber comes increasingly confused, sluggish and tired, incapable of walking and behaving strangely.

Look out for:

  • Disorientation, confusion, hallucinations, talking nonsense
  • Lack of coordination, staggering, inability to walk
  • Irrational behaviour
  • Severe headache, sometimes accompanied by nausea and vomiting

HACE cannot be treated without immediate evacuation to a medical facility.

How is Altitude Sickness Diagnosed?

In our daily health checks, Our  guides will use a pulse oximeter to measure your oxygen saturation and pulse rate and use this data and any symptoms you are presenting to build up a picture of your situation.

Lake Louise Scoring System

Developed in 1991 and reviewed as recently as 2018, the Lake Louise Scoring System remains the basis for most diagnoses in the field of a climber’s condition. Climbing Kilimanjaro guides use this as a framework when they assess your condition. The ‘score’ attaches a number depending on the severity of your condition.


  • 0—None at all
  • 1—A mild headache
  • 2—Moderate headache
  • 3—Severe headache, incapacitating

Gastrointestinal symptoms

  • 0—Good appetite
  • 1—Poor appetite or nausea
  • 2—Moderate nausea or vomiting
  • 3—Severe nausea and vomiting, incapacitating

Fatigue and weakness

  • 0—Not tired or weak
  • 1—Mild fatigue/weakness
  • 2—Moderate fatigue/weakness
  • 3—Severe fatigue/weakness, incapacitating


  • 0—No dizziness/light-headedness
  • 1—Mild dizziness/light-headedness
  • 2—Moderate dizziness/light-headedness
  • 3—Severe dizziness/light-headedness, incapacitating

AMS Clinical Functional Score

Overall, if you had AMS symptoms, how did they affect your activities?

  • 0—Not at all
  • 1—Symptoms present but did not force any change in activity or itinerary
  • 2—My symptoms caused me to stop the ascent or to go down on my power
  • 3—Had to be evacuated to a lower altitude

[Source: High Altitude Medicine and Biology]

Acclimatization: Preventing Kilimanjaro Altitude Sickness

The term acclimatization or “acclimatization” refers to the body’s compensatory processes to adapt to the low-oxygen, low-atmospheric pressure environment. 

Your body will start to make adaptive changes to compensate from day one.

Things you’ll notice:

  • Breathing deeper, sometimes faster
  • Elevated resting heart rate
  • Potentially higher blood pressure.

As you ascend slowly, your body has certain mechanisms it uses to adapt:

  • Producing more of the oxygen-carrying hemoglobin
  • Higher erythropoietin production is a hormone from the kidneys that increases the manufacture of red blood cells
  • A lower volume of plasma can increase the risk of dehydration.
  • Higher kidney function as excess bicarbonate ions is excreted due to changing acid/alkali balance of the blood.

These changes are a gradual process, which is why the best and safest summit success rates are had on routes with a good acclimatization protocol. The longer it takes to reach a high altitude, the longer your body has to adapt.

Building in acclimatization days “hike high, sleep low” and rest days increases your chances of adequate adaptation, resulting in a lower incidence of mountain sickness.

Acclimatization is a complicated process; some people seem to have no problem. There are no tricks or hacks. It’s a matter of time, although the medication Diamox has been shown to regulate the body’s natural acclimatization processes and can help speed it up.

How to Avoid Kilimanjaro Altitude Sickness 

  • Take a longer route: Instead of choosing the quickest way up Kilimanjaro, opt for a route that builds in some acclimatization time. Also, Kilimanjaro climb training and preparation is very important.
  • Hike slowly: You’ll hear your guides reminding you of this “pole pole” (slowly in Swahili). You don’t want to tire yourself out; always try to be the last person into camp.
  • Walk high, Sleep low: It is best to climb higher each day gradually, then descend lower to sleep and lets you gradually become accustomed to lower pressures and recover somewhat overnight.
  • Conserve Energy: Even if you’re very fit, you need to conserve your energy to avoid over-exertion. Fatigue is believed to be a major contributor to AMS.
  • Stay hydrated: Keeping your fluids up prevents dehydration in the dry air, compromising your ability to acclimatize.
  • Diamox: Ask your doctor if Diamox is right for you.
  • Don’t climb higher if you are suffering any symptoms of altitude sickness.
  • Avoid narcotic pain killers: sleeping pills, alcohol or stimulants.
  • Always tell your guide: if you have a headache, nausea or any other symptom.
  • Keep eating, particularly carbohydrates: The US Army studies show that carbohydrates increase ventilation and are the most efficient fuel for high altitude exertion.
  • Stay warm: Hypothermia is dangerous; never stay in wet clothes.

Effects of exposure to low atmospheric pressure

Low oxygen saturation

At high altitudes and low pressures, each breath takes less oxygen and transfers less to the blood. Blood with low levels of oxygen is said to be poorly saturated. Having slightly low oxygen saturation can lead to fatigue and feeling breathless. Severe low oxygen saturation can cause impaired mental functions, reduce your decision-making ability, and have other dangerous effects. All our guides have pulse-oxymeters to check your oxygen saturation daily. 
  1. Cerebral oedema
Severely reduced air pressure can cause fluid to collect in the sinuses and air cavities in the skull. Initially, it presents as a mild headache but can eventually cause disorientation, coma and even death. Cerebral oedema can suddenly be present and is an extremely serious medical issue.
  1. Pulmonary oedema
This is caused by reduced air pressure in the lungs. Fluid sometimes begins to seep from the lung tissues into the lungs’ air spaces, making breathing even more difficult. This often presents like pneumonia and is most likely to occur during sleep.

Does Altitude Training help acclimatization?

Altitude Training is becoming increasingly popular amongst would-be mountaineers. Some athletes use these training protocols to enhance performance, and studies have shown a “per-acclimatization” process.

The protocols vary from training in a simulated altitude chamber, sleeping in a hypnotic tent, and even intermittent exposure to hypoxic air at rest. You can read us a depth guide to Kilimanjaro altitude training for more information.

The best pre-acclimatization method would be to climb Mt Meru or some peaks in your home country before travelling to Kilimanjaro. This isn’t possible for everyone, nor is it necessary, but if you have access to some high altitude, you’ll get a good idea of how well you acclimatize.

Effects of Altitude on existing Conditions

Your doctor will advise you of whether your medical history prevents you from travelling to altitude. Many people with well-controlled pre-existing conditions can climb Kilimanjaro successfully.

Anyone with heart, lung or neurological conditions will need to have a medical sign-off from their doctor before joining one of our climbs. Your doctor needs to assess how the altitude may affect your current medications and condition. Certain medical conditions may make getting adequate travel insurance more difficult.

Effects of Altitude on Sleep: Cheyne-Stokes Breathing

One of the main reasons for sleep disturbance at altitude is periodic breathing. This is not necessarily associated with altitude sickness but can be uncomfortable and disruptive. The Institute for Altitude Medicine explains that it’s a “battle in the body over control of breathing during sleep”. The oxygen sensors tell the parasympathetic nervous system to breathe more deeply, whilst the carbon dioxide sensors tell it to stop.

The result is usually deep breathing followed by the breathing stops, and then a deep breath as it restarts. Diamox often helps with this condition.

Other Health Considerations on Kilimanjaro

While altitude sickness is the main concern, you need to take a proactive view of your health whilst climbing.


  • Never stay in wet clothes. Whether from rainfall or sweat, once you stop moving, a slight chill can turn to hypothermia in a short time, especially higher up the mountain. Make sure you carry adequate layers in your day pack, as rapid changes in temperature are quite common as you ascend.

The Sun’s Rays

  • Always wear sunscreen, preferably factor 40+, cover exposed parts of your body, including your head and neck. There is less atmosphere to filter out the harmful UV rays as you ascend, and the sun’s rays are harsh.
  • Most importantly, wear sunglasses that block 100% of the UV rays. Wraparound glasses are best to prevent reflected UV off glaciers and snow from damaging your eyes. Snow blindness is not common, but it’s a definite risk if you don’t protect your eyes.

Gastrointestinal issues

  • Any travel to remote places comes with a risk of gastrointestinal trouble. Different foods, sub-standard hygiene, and exposure to bacteria and viruses can cause stomach problems. Always use anti-bacterial gel or wipes on your hands, especially before eating.
  • Your main risk for stomach trouble is before your climb. Avoid eating at street stalls; stay away from tap water, salads, and fruit you can’t peel. On the mountain, we adhere to strict food hygiene protocols and provide safe, purified water.

Eco-Africa Climbing Kilimanjaro Safety Procedures

At Eco-Africa Climbing, we take your safety very seriously. Our trained Mountain guides will monitor you closely, but they also need your help. If you feel unwell, you should inform your guide immediately. Keep an eye on other members of your group. Tell your guide if you see someone behaving strangely or appear to be suffering.

Your guide will check your oxygen saturation with a pulse oximeter twice a day, question how you feel, and listen to your chest for unusual lung sounds. Catching it early is the best way to prevent mild altitude sickness escalating.

Our Guides carry emergency oxygen on every climb. If your oxygen level; is below 80%, you will be required to submit to another test every half hour for the next two hours. If your saturation does not rise to at least 75%, you will be required to descend immediately. If your saturation is at least 75%, you will be allowed to continue subject to close monitoring. If your condition worsens, you must notify your guide immediately and begin the descent.

If a climber is suffering and cannot proceed, they will have to descend.

Our client descend protocol

If our guides believe you may be in poor health or allow you to continue the climb may be dangerous, they will require you to begin your descent immediately. If that decision is made, it will be according to this protocol:

We have partnered with KILIMEDIAR for Kilimanjaro Helicopter Rescue for emergency evacuation, but the climber required travel insurance coverage up to 6000 meters.

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