Kilimanjaro is not a dangerous mountain in the technical sense. The risks are altitude, cold, and the occasional twisted ankle on scree. What matters is whether the people you're with are set up to spot a problem early and act on it.
What a properly equipped crew carries
A pulse oximeter, used twice a day on every climber. Bottled oxygen, for emergencies and for assisting a descent. A comprehensive first-aid kit. A means of calling for help. And enough guides that one can take a single climber down without abandoning everybody else, which in practice means an assistant guide for every few climbers.
How an evacuation works
Nearly always on foot, and quickly. A guide walks the affected climber down, losing height as fast as is safe, because height is the medicine. If someone can't walk, the camps have one-wheeled stretchers and the crew run them down the path. It's rough and it's effective.
Helicopter evacuation exists and is run by private operators. It depends on weather, daylight and whether there's somewhere to land, and it is expensive enough that your insurance needs to cover it. Treat it as a possible help rather than a plan.
The rescue fee
The park charges a rescue fee as part of every climbing permit. It covers the park's own ground rescue, not a private helicopter and not your hospital bill. Don't mistake it for insurance.
The guide's authority
Your lead guide can end your climb, and that decision isn't negotiable. People paying several thousand dollars sometimes want to argue. Please don't. A guide who sends a client down on a bad reading is doing precisely the job you hired them for, and the ones who can be talked round are the ones to worry about.
Other things that actually go wrong
Sunburn, at a severity people don't expect. Dehydration. Stomach bugs passed round a mess tent. Blisters from boots worn new. Twisted ankles on the descent, when you're tired and moving fast on loose ground. None of these are dramatic, and together they account for most of the misery on the mountain.
Questions before you book
How many guides for our group size? Do you carry oxygen and a pulse oximeter, and how often are we checked? What's the procedure if one person has to descend at night? Is the crew insured, and are they paid the agreed rates? A company that runs a safe mountain will answer all five immediately.
What you can do for yourself
Report symptoms early, drink what you're told to, walk slower than feels necessary, and keep a head torch and your warm layer where you can reach them in the dark. Know your own insurance details. And watch the people you're walking with, because the first person to notice that someone has gone quiet and started stumbling is usually their friend, not their guide.