Kilimanjaro Altitude Sickness - Prevention & Treatment

Understanding Altitude Sickness on Kilimanjaro

Altitude sickness is the number one reason climbers fail to reach the summit of Kilimanjaro. It is not a matter of fitness, willpower, or experience - it is a physiological response to reduced oxygen availability that affects everyone differently and somewhat unpredictably. Understanding how altitude affects your body, recognising the warning signs, and knowing how to respond can make the difference between a successful summit and a forced retreat.

How Altitude Affects Your Body

At sea level, the air contains approximately 21% oxygen. This percentage does not change with altitude - the air at the summit of Kilimanjaro still contains 21% oxygen. What changes is the air pressure. At 5,895 metres, atmospheric pressure is roughly half what it is at sea level, which means each breath delivers approximately 50% less oxygen to your lungs.

Your body responds to this oxygen deficit through a process called acclimatization:

• Increased breathing rate - your respiratory system works harder to capture more oxygen
• Increased heart rate - your cardiovascular system pumps blood faster to distribute the available oxygen
• Increased red blood cell production - over days, your body produces more haemoglobin to carry oxygen more efficiently
• Changes in blood chemistry - your kidneys adjust the pH of your blood to compensate for the increased breathing rate

This process takes time. When you ascend faster than your body can acclimatize, symptoms of altitude sickness develop.

Types of Altitude Sickness

Acute Mountain Sickness (AMS)

AMS is the mildest and most common form, affecting 50-75% of Kilimanjaro climbers to some degree. It typically appears 6-12 hours after arriving at a new altitude and can last 1-3 days.

Symptoms (Lake Louise Score criteria):

• Headache - the hallmark symptom, often described as a dull, persistent pressure
• Nausea or vomiting
• Fatigue and weakness disproportionate to the effort being made
• Dizziness or light-headedness
• Loss of appetite
• Difficulty sleeping (insomnia is extremely common above 3,500m)

Mild AMS is uncomfortable but not dangerous. Most climbers on Kilimanjaro experience at least a headache and some fatigue above 3,500 metres. These symptoms are managed with rest, hydration, and painkillers, and typically resolve as your body acclimatizes.

Moderate AMS features worsening symptoms that do not improve with rest and medication. A severe persistent headache, repeated vomiting, and marked fatigue are warning signs that the climb should be paused or descent initiated.

High Altitude Cerebral Edema (HACE)

HACE is a severe, life-threatening progression of AMS where fluid accumulates in the brain, causing swelling.

Warning signs:

• Severe headache that does not respond to painkillers
• Confusion, disorientation, irrational behaviour
• Ataxia - loss of coordination, stumbling, inability to walk a straight line (the definitive test is whether the climber can walk heel-to-toe in a straight line)
• Drowsiness progressing to unconsciousness
• Hallucinations

HACE requires immediate descent. Every hour at the same altitude increases the danger. Descent of even 500-1,000 metres typically produces rapid improvement.

High Altitude Pulmonary Edema (HAPE)

HAPE occurs when fluid accumulates in the lungs, reducing oxygen exchange. It can develop independently of AMS or alongside it.

Warning signs:

• Extreme breathlessness, even at rest
• Persistent cough - dry at first, potentially producing pink or frothy sputum as the condition worsens
• Gurgling or crackling sounds when breathing
• Rapid heart rate at rest
• Blue tinge to lips or fingernails (cyanosis)
• Inability to lie flat without breathlessness

HAPE is a medical emergency requiring immediate descent. It can deteriorate rapidly and is the most common cause of altitude-related death.

Prevention: The Seven Pillars

1. Ascend Slowly (Pole Pole)

The golden rule of altitude acclimatization. Above 2,500 metres, your sleeping altitude should increase by no more than 300-500 metres per day. On Kilimanjaro, the route itinerary manages this for you - which is precisely why choosing a longer route is so important. A 9-day Northern Circuit itinerary gives your body nearly twice as many days to acclimatize as a 5-day Marangu trek.

2. Walk High, Sleep Low

The most effective acclimatization technique. Several Kilimanjaro routes incorporate this by design - the Lava Tower detour on Machame and Lemosho routes takes you to 4,630 metres during the day before sleeping at 3,960 metres. The Rongai Route's acclimatization hike from Mawenzi Tarn serves the same purpose.

3. Hydrate Aggressively

Dehydration worsens AMS symptoms and impairs acclimatization. Aim for 3-4 litres of water per day on the mountain. Your urine should be clear to pale yellow - dark urine is a sign you are not drinking enough. The dry air above 3,500 metres causes significant moisture loss through breathing that you may not notice.

Practical tips:

• Drink water consistently throughout the day, not in large volumes at once
• Herbal tea at camp adds variety and warmth
• Add electrolyte tablets or powder to maintain salt balance
• Avoid caffeinated drinks in excess (mild diuretic effect)

4. Use Diamox (Acetazolamide)

Diamox is the most widely used pharmaceutical aid for altitude acclimatization. It works by increasing the acidity of your blood, which stimulates your respiratory centre to breathe faster and deeper, improving oxygen uptake.

Recommended protocol:

• Dosage: 125mg twice daily (some doctors recommend 250mg twice daily; research suggests the lower dose is equally effective with fewer side effects)
• Start: 1 day before reaching 2,500 metres (i.e., the day before your climb starts)
• Continue: Through the ascent phase. Some climbers continue through descent; others stop after summit day.
• Side effects: Tingling in fingers, toes, and lips; increased urination (so drink more); altered taste of carbonated drinks; rarely, nausea

Important: Diamox requires a prescription. Obtain it from your doctor before your trip. If you are allergic to sulfa drugs, Diamox is not safe for you - inform your doctor.

Myth to dispel: Diamox does not "mask" symptoms of dangerous altitude sickness. You will still feel the symptoms of HACE or HAPE if they develop. Diamox simply helps your body acclimatize faster.

5. Avoid Alcohol

Alcohol dehydrates you, disrupts sleep, and impairs your body's acclimatization response. Avoid alcohol entirely on the mountain. The celebratory beer can wait until you are back in Moshi.

6. Eat Well

Your body burns 4,000-6,000 calories per day at altitude. Loss of appetite is common, but forcing yourself to eat is important. Carbohydrate-rich foods are easiest to digest at altitude and provide the quickest energy. Your mountain chef will prepare hot, nutritious meals - eat as much as you can.

7. Sleep Well

Insomnia is one of the most frustrating aspects of altitude. Your breathing pattern changes at altitude - periodic breathing (irregular breathing with pauses) is very common and can be alarming but is generally harmless. Tips for better sleep:

• Use earplugs and an eye mask
• Elevate your upper body slightly (prop your pack under your sleeping mat)
• Avoid sleeping pills (they suppress breathing)
• Do not worry about poor sleep - it is normal and does not significantly impair your climb if you rest well during breaks

When to Descend

The cardinal rules of altitude safety are simple and must never be broken:

1. Never ascend with worsening symptoms. If your headache is getting worse, not better, do not continue upward.
2. Descend if symptoms do not improve after 24 hours at the same altitude.
3. Descend immediately for any signs of HACE or HAPE - confusion, ataxia, breathlessness at rest, persistent cough.
4. A climber with AMS who becomes ataxic has HACE until proven otherwise. Descend.

Descent is the treatment. Even 500 metres of descent typically produces noticeable improvement in symptoms. Do not let ambition override safety - the summit is not worth your health or your life.

Why Longer Routes Equal Better Acclimatization

The data from thousands of Kilimanjaro climbs shows a clear relationship:

Each additional day gives your body roughly 10-15% better acclimatization. The conclusion is straightforward: if you want to maximise your safety and your summit chances, choose the longest route your schedule and budget allow.