Altitude Sickness on Kilimanjaro: Symptoms, Diamox and When to Turn Back

Almost everybody feels the altitude on Kilimanjaro. A headache at Shira, a bad night at Barranco, no appetite at Karanga. That is normal and it is not what should worry you.

What matters is knowing where normal ends. Two forms of altitude illness on this mountain are genuinely dangerous, both have clear warning signs, and both are survivable if they are recognised early and acted on. This is the part of your preparation that is worth reading twice.

This article is written by mountain operators, not doctors. It describes what we see and what our guides are trained to do. Speak to a travel medicine clinic before you climb, particularly about Diamox and about any medication you already take.

Why Kilimanjaro is unusual

You are driven to a gate at around 1,800m and you stand on the summit at 5,895m less than a week later. There is no trek in, no gradual approach, no week of walking at moderate height first. You go from farmland to arctic conditions faster than almost anywhere else people routinely go this high.

At Uhuru Peak there is roughly half the oxygen available at sea level. Your body can adapt to that, but it needs time, and the mountain’s profile does not naturally give you much. That is the entire argument for longer routes.

Mild acute mountain sickness: what most people get

AMS is diagnosed on a headache plus at least one of the following, after a gain in altitude.

• Nausea, or loss of appetite
• Fatigue or weakness beyond the day’s effort
• Dizziness or light headedness
• Difficulty sleeping, and the odd breathing pattern where you seem to stop breathing then gasp, which is unsettling but not itself dangerous

Mild AMS is common and manageable. The response is to stop gaining altitude, drink, eat, take simple painkillers, and see how you are in the morning. If it settles, you continue. If it worsens, you go down. It is not a sign you are failing, and it is not something to hide from your guide.

The two that kill

HACE, high altitude cerebral oedema. Fluid on the brain. The signs are neurological rather than just unpleasant: confusion, strange or uncharacteristic behaviour, drowsiness that is hard to rouse someone from, severe headache that does not respond to painkillers, and loss of coordination.

Guides test for that last one constantly. Ask the person to walk heel to toe along a straight line. Somebody who cannot do it, and who could yesterday, is descending tonight. That test, called ataxia, is the single most useful thing a non medic can check on this mountain.

HAPE, high altitude pulmonary oedema. Fluid in the lungs. Breathlessness at rest, which is the key distinction because everybody is breathless walking uphill at 4,500m. A persistent dry cough turning wet, sometimes with pink or frothy sputum, a crackling sound when breathing, blue tinged lips or fingernails, and a heart rate that stays high while resting.

Both are emergencies. Both are treated the same way: go down, immediately, at night if necessary, with oxygen if it is available. Neither improves by waiting to see how the morning looks.

Diamox: what it does and what it does not

Acetazolamide, sold as Diamox, makes your blood slightly more acidic, which prompts you to breathe more deeply and speeds up genuine acclimatisation. It works, it is well studied, and it is widely used on this mountain. A typical prophylactic dose is 125mg twice a day starting a day or two before you begin gaining altitude, but that is your doctor’s decision, not ours.

Two things worth knowing. It makes you urinate more, so your fluid intake has to go up with it. And it commonly causes tingling in the fingers, toes and lips, plus a strange metallic taste that ruins fizzy drinks. Both are harmless. Trying a dose at home before you travel is sensible, so you find out on your sofa rather than at Shira Camp.

The important caveat: Diamox helps you acclimatise, it does not make you immune. It can mask mild symptoms while the underlying problem continues. People on Diamox still get HACE and HAPE. It is a useful aid, not a licence to go higher faster.

What your guides should be doing

On a properly run climb, you are checked twice a day, morning and evening. Oxygen saturation and pulse are taken with a fingertip oximeter, and you are asked a standard set of questions about headache, appetite, sleep and dizziness, scored consistently so a trend is visible.

The trend is what matters more than any single reading. Saturation in the 80s is unremarkable at 4,600m. Saturation falling steadily across three checks, in someone whose appetite has gone and who is stumbling, is a decision.

Bottled oxygen should be on the mountain for emergency use, and a stretcher should be available. Ask any operator to confirm both before you book.

Nine things that genuinely help

• Go slowly. Pole pole is not a cliché, it is the single most effective intervention. If you are comfortably out of breath, you are going too fast.
• Drink 4 to 5 litres a day. Dehydration produces a headache indistinguishable from AMS, and you will lose fluid faster than you expect in dry, cold, high air.
• Eat, even without appetite. Appetite disappears at altitude exactly when you need the calories most. Eat anyway.
• Climb high, sleep low where the route allows it. The Lava Tower detour on Machame and Lemosho exists for this reason, and it is worth the extra effort.
• Take the longer route. The most reliable purchase you can make is days.
• Skip the alcohol and go easy on sleeping tablets, which suppress breathing.
• Keep warm. Being cold makes everything else worse.
• Tell your guide the truth. Downplaying a symptom to avoid being turned around is how a manageable problem becomes a rescue.
• Watch your companions. The person with HACE is often the last to notice.

The only real cure

Descent. Not rest, not oxygen, not medication. Those buy time and make the descent survivable, but going down is the treatment. Dropping 500 to 1,000m usually produces dramatic improvement within hours.

Turning back a few hundred metres below the summit is the hardest decision on this mountain, and any guide worth their licence will make it for you if you cannot. The mountain will still be there. Our guides are trained and equipped to make that call, and they have our full backing when they do.

If you would like to talk through route choice, acclimatisation profiles or a specific medical concern before you commit, get in touch and we will give you a straight answer.