High Altitude Acclimatization On Kilimanjaro
Everything you need to know to safely reach the top of Africa.
Thousands of travelers fly to Tanzania every year to attempt to climb the highest point on
the African continent, Mount Kilimanjaro (5.895 meters). Some of them return home without
reaching the summit. This happens for a variety of reasons, but the main cause is due to
poor altitude acclimatization.
On the internet, you can find hundreds of materials on this issue. Unfortunately, most of
them resemble scientific articles, using terminology which is difficult for the average
traveler to understand. We will try to explain in simple terms what high-altitude
acclimatization is and what you need to do to make your acclimatization successful.
Please note: although we have successfully conducted many expeditions to Kilimanjaro and
have accumulated a wealth of experience in such matters, we are not doctors. The author
of this article has a certificate of completion of training in the provision of medical care in
mountain conditions, but I cannot give medical advice. Treat this information as a reference,
and if you have concerns about your health before climbing, be sure to consult with your
What is high-altitude acclimatization in general?
As you make plans for Kilimanjaro, you will likely see or hear the phrase “high-altitude
acclimatization” frequently. To be brief, high-altitude acclimatization refers to physical
changes that occur in your body so that you feel better and your body can function well at
A logical question is why do some climbers experience feeling poorly, physically, as they
ascend into higher altitudes?
The thing is that the higher we go, the lower the atmospheric pressure becomes. As a result,
the distance between oxygen molecules in the air we breathe spreads – there is not enough
pressure to “hold” them together. As a result, with each breath, our body receives less
oxygen than at the altitudes with which we are accustomed.
Oxygen is necessary for the proper functioning of the circulatory system, the brain and
other life-sustaining functions.
If you reside at sea level, your body is accustomed to a certain concentration of oxygen. As
you ascend Mt Kilimanjaro, the concentration of oxygen available gradually reduces until it
is about 40% less than sea level at the final summit.
Note: The proportion of oxygen in the atmosphere as a whole (approximately 20%) is
unchanged, whether at sea level or Kilimanjaro. This proportion is the combination of oxygen,
nitrogen and carbon dioxide that make up our atmosphere.
Feeling a lack of oxygen, the body begins to actively adapt to new conditions. There are many
physiological changes, of which the most significant are:
The respiration rate increases. Our body tries to compensate for less oxygen in each
breath by taking more frequent breaths, so that the total number of molecules
received is approximately the same as your body is used to.
The parts of the lungs that are usually “conserved” begin to turn on – our body has
reserved them for such situations.
The body begins to produce special enzymes that “squeeze” oxygen from the received
hemoglobin and send it to the circulatory system, partially replenishing the supply.
The number of red blood cells in our blood increases significantly. This allows
available oxygen molecules to be delivered to vital organs at a faster rate.
This is how our body tries to bring the oxygen level back to the level we need. During daily medical examinations, our guides will measure your oxygen with a special device- an oximeter. Blood oxygen levels help our team understand how well your acclimatization is.
Allowable Oxygen Level
The normal level of oxygen in the blood (sometimes referred to as saturation) is
between 95-99%. People suffering from chronic lung diseases or cardiovascular
insufficiency may have figures between 92% -94%.
In the mountains, the situation changes and oxygen saturation may drop. During medical
examinations, our guides will pay attention to the following indicators:
Between 90% and 99% – excellent indicators! In the absence of other complaints,
we can confidently say this climber is ready to continue the ascent.
80 – 89% – good indicators, which suggest that acclimatization is relatively
successful, but you need to pay attention to the general well-being. Be sure to tell
your guide if you have a headache, indigestion, nausea, or other discomfort. These
may be the first symptoms of an onset of altitude sickness.
Inform your guide of any ailments, even insignificant ones. If you feel unwell –
immediately inform your guide! His job is not only to guide you to the top of Mount
Kilimanjaro, but also to ensure your safety.
All of our head guides have received special medical training in the mountains and are
internationally certified Wilderness First Responders.
70% – 79% – this is a clear signal that something is wrong. Your guides will start
asking questions in order to establish the reasons why acclimatization is not going
appropriately and to ensure your health and safety. This does not mean that you have
to stop climbing and go down. The guides will do their best to keep you climbing.
However, your health and safety remains our top priority. If there are no other
complaints, the guides will let you breathe oxygen from a special cylinder. Paired with
extra rest, this will raise your blood oxygen levels and help your body. The oxygen
saturation will most likely be restored and you will be able to continue climbing. If, in
addition to low oxygen levels, you also have other complaints, the guides will offer
you medicine for common mountain-climbing concerns.
65 – 70% – these levels are a serious reason to think that acclimatization has not
occurred and the body does not have time to adapt to the altitude. Usually, such a
low oxygen concentration is diagnosed during an evening physical. If, in addition to
low oxygen saturation, the climber also has a severe headache, nausea and other
symptoms of altitude sickness, the guides will put an oxygen mask on the climber and
escort him or her to the nearest evacuation point. From there, the climber will be
picked up either by car or helicopter. If needed, a stretcher can be used to carry
the ill climber, instead of walking to the evacuation point.
Please note that some camps on Kilimanjaro cannot be reached by an evacuation vehicle or
helicopter. From these locations evacuation is carried out on foot (or on a stretcher) until
reaching the National Park exit.
The decision to evacuate a climber is always taken very seriously by our guides. We
understand that for many, climbing Kilimanjaro is an once-in-a-lifetime dream, and is quite
expensive. However, your health and life are priceless and there is no adventure or dream worth such risk. You can always return to Kilimanjaro and try again. Of the thousands of
participants in our annual expeditions, several dozen are forced to stop climbing and turn
down. Most of them return the following year and successfully reach the summit.
We understand how important it is for many to be on top, and we do our best to ensure that
all participants achieve their goal. In our expeditions, we have selected the most balanced
meal plans in the mountains, excellent equipment, and undergo daily medical examinations in
the morning and in the evening all to help you achieve this goal. The guides help climbers find
the right walking pace, carry bottled oxygen and do much more to ensure that all travelers
reach Uhuru Peak (5.895 m).
If for some reason this does not happen, our company offers substantial discounts for
everyone who wants to make a second attempt with us.
Therefore, if the guide believes that further ascent is dangerous, the best thing you can do
is to descend following the instructions of the guide and start planning for a new expedition.
If the body is experiencing problems with acclimatization to the altitude, it is necessary to
urgently go down. As soon as the body receives more oxygen, the body will begin to recover
and begin to return to normal. If you stay at a high elevation, then over time, you may develop
a severe degree of altitude sickness. This is an extremely dangerous condition that occurs
in the form of cerebral edema or pulmonary edema, and in especially difficult cases, both.
If you do not evacuate the victim in time and do not provide medical assistance, complications
can be fatal.
It is critical to distinguish the symptoms that accompany normal altitude acclimatization
from the symptoms of altitude sickness. Altitude Sickness indicates that the climber is
clearly unable to adapt to altitude and must be evacuated. The main indicator here is the
level of oxygen in the blood.
The other indicators are considered by guides in aggregate. The following factors may
indicate the onset of altitude sickness:
Severe, persistent headache
Serious sleep disturbance, complete inability to fall asleep at night
Nausea and vomiting
This may seem confusing, as these symptoms are the same as the usual acclimatization
However, with proper acclimatization, the severity is less and symptoms should pass
in a day, or less. One of the key tasks of our guides during the ascent is to determine the severity of symptoms and decide what to do next – let the expedition member breathe
oxygen from a cylinder and support his/her body with special drugs, or if it is necessary to
Pulmonary Edema occurs when light-colored blood plasma builds up in the tissues of the
lungs. When you try to inhale, the fluid foams and prevents the lungs from performing their
function – to supply the body with oxygen. It is the most common of all mountain-related
health issues and is perhaps the leading cause of death in the mountains.
Pulmonary edema occurs in three stages, each new stage increasing with intensity of
The following symptoms indicate the first stage of pulmonary edema:
The patient can stand on his/her feet, but movement is difficult, in some cases the
patient cannot walk at all;
There is no urination for a long time (8-12 hours);
Breathing problems are present, the patient begins to cough dryly or clench his teeth
while trying to inhale;
Breathing intensifies and becomes more rapid
The skin may become moist and pale;
Lips, ears and nail beds may turn blue-ish
Pulse increases noticeably;
The patient tries to lie down, but cannot stay in a horizontal position for a long time;
In some cases, the patient’s temperature rises, indicating a fever.
If the patient does not descend to a lower altitude quickly and receive medical attention,
the second stage of the condition will begin to set in.
Symptoms of the second stage of pulmonary edema include:
Inability to stand, but also cannot lie down. Patient takes a half-sitting-reclining
position. The patient may try to lie down, but begins to choke due to fluid in lungs
and then sits up;
A dry cough is replaced by a wet one. May cough up phlegm;
Rapid pulse rate;
The patient is constantly thirsty;
If the patient remains at the high altitude, after approximately 8-10 hrs the third stage
A sharp, piercing headache;
Blood pressure rises – the upper arterial pressure reaches 150-170, and the lower –
90-100 mm Hg;
Blood appears in the sputum that is coughed up and other discharge turns red;
Breathing is difficult, wheezing from the chest is clearly audible;
Pinkish foam begins to ooze from the nose and mouth
If the victim is still at the height, after the third stage he falls into a coma.
Cerebral Edema occurs because the amount of fluid in the capillaries of the brain decreases.
As a result, the brain swells and grows in size. In advanced stages, the cerebellum begins to
press on the spinal cord stem and destroys its vital areas.
Like pulmonary edema, cerebral edema occurs in three stages.
In the first stage, the following symptoms are observed:
The head will feel like lead, acute “bursting” pains, and the brain seems to be cramped
in the cranium;
The victim begins to experience coordination problems; walking as if intoxicated, the
patient cannot walk along a straight line;
The person becomes very apathetic, detached from everything that happening;
The patient has difficulty answering questions and responding to requests from
The difference between cerebral edema and pulmonary edema is that the victim can be in a
If you do not descend, then in about ten hours the second stage of cerebral edema will set
in, which is characterized by the following:
Significant increase in severity of headache
The patient begins to behave strangely and does not understand what is happening;
aggressive episodes, euphoria or bizarre behaviors may manifest. The patient may
actively resist attempts to evacuate, threaten the team and other climbers.
Over time, the consciousness is inhibited. The patient may fail to recognize members
of the climbing team or have other cognitive delays.
Next is the third stage, which is marked by:
The pupils of the eyes dilate and there is no reaction to light;
The patient periodically loses consciousness, and, upon regaining consciousness,
behaves irrationally and confused;
The limbs become numb and lose sensitivity;
The headache increases in severity.
As in the case of pulmonary edema, after the third stage, the victim falls into a coma.
The main rules for successful acclimatization
Duet to our recommendations, the vast majority of participants who climb Kilimanjaro
successfully acclimatize to altitude. Some do not feel anything at all, while others adapt
with minimal discomfort in the first days of the expedition. Some discomfort is normal and
is why our guides perform regular health checkups. A climber may feel uncomfortable, but
based on oximeter readings and other symptoms, be acclimatizing appropriately.
In order to successfully adapt to altitude, it is important to remember the following simple,
but very important rules of acclimatization:
Choose routes lasting seven days or more. As we explained above, during acclimatization,
many processes take place in the human body, and in order to successfully adapt to altitude,
the body needs two things – time and energy.
As practice shows, six days to the top (this is how much time it takes to climb to the top of
Kilimanjaro on seven-day routes; the additional day is needed for the descent) is sufficient
for most travelers. Transitions on such programs are rather moderate, especially for the
first days of the trek. Upon arrival at the camp, participants in the seven-day climb will have
significantly more time to rest and recover than those who chose the six or five-day program
to conquer Kilimanjaro.
It is for this reason that most of our group ascents of Kilimanjaro are seven-day routes.
They are well suited for both beginners and experienced climbers without high-altitude
Travelers who haven’t played sports for a very long time or just want to take the route at
a more relaxed pace are advised to pay attention to the eight-day routes (which are seven
days of climbing up Kilimanjaro, and an additional day for descent).
Visitors to our site may be confused by the published 5- and 6-day programs. We publish
them for experienced mountain hikers who have already gained acclimatization before visiting Kilimanjaro and who do not need to worry about the body taking longer to adapt to
the high altitude.
Another option for acclimatization is to tackle Mt Meru first, Tanzania’s second-highest
peak (4566 m). After summiting that mountain, you can safely choose a five-day program on
Kilimanjaro, because your body will be sufficiently prepared for the altitude, despite the
Drink more water! Your body uses a lot of water when climbing a mountain, not only because
of physical exertion, but also to perform the additional functions to adapt to the higher
altitude. It is important to constantly replenish the supply of water in your body – climbers
on Kilimanjaro must drink at least 3-4 liters of water per day.
We recommend drinking a liter and a half during the transition from camp to camp and
“finishing off” the rest upon arrival. It is better to drink in small sips, but more often. During
the trek, our guides will make a rest stop every 25-30 minutes and remind climbers that it’s
time to take a couple of sips of water.
Eat well. The body needs a lot of energy to successfully acclimatize. For this you need to
eat well. Food for the expedition members is prepared by our team of mountain chefs. They
offer a variety of hot meals and drinks for breakfast, lunch and dinner. We designed our
mountain menu to be tasty and balanced. Every day, chefs will offer a delicious selection of
cereals, chicken, beef, eggs, spaghetti, vegetables, fresh fruits, soups and more.
Unfortunately, sometimes new climbers find that their appetite disappears on the mountain. Even so, the body needs energy, and you have to force yourself to eat.
Walk high – sleep low. This is a well-known mountaineering saying that underlies the so-called “step” acclimatization.
Indeed, the body adapts better if the daytime transition takes
place at an altitude, and climbers sleep at a slightly lower elevation than which they trekked during the day.
You do not need to worry about following this principle – the guides will regularly take you to acclimatization points. We have already mapped out each route and know the specific acclimatization profile, we just ask that you trust us and participate in additional brief hikes after reaching camp. You will climb to a higher point and then return to camp for a rest. As much as you would like to miss the acclimatization hike after the day’s hike, be sure to
participate in them! As practice shows, for everyone who goes on acclimatization hikes the process of adaptation to altitude is much faster than for those who do not.
Take your time. The slower your climbing pace, the better for the body. It is better for
your body to spend more resources on acclimatization rather than recuperating after brisk
walking. Ideally, you should walk two to three times slower on the slopes of Kilimanjaro than
you would normally walk down the street at home.
Guides and porters will constantly repeat the phrase “pole-pole”. In Swahili it means “slowly”.
This is one of the best tips for a successful ascent of Kilimanjaro – as practice shows, almost
all climbers who take a measured pace from the very beginning of the expedition successfully
acclimatize and reach Uhuru Peak (5.895 m) without any difficulties.
Follow these simple rules, and do not hesitate to talk about your health at morning and
evening medical examinations. Listen to the advice of Shiri Adventures guides and your
ascent to Kilimanjaro will be successful.