It is important to remember that altitude sickness is a serious and real risk when climbing Kilimanjaro, killing several climbers every year.
While most people will get a minor headache and some nausea as they ascend, almost everyone will feel the effects of the altitude above 15,000 ft. Serious signs of altitude or Acute Mountain Sickness (AMS) include a severe headache , vomiting, dizziness, staggering or slurring of speech. These symptoms are a signal that your body is not adjusting to the lack of oxygen as you ascend. The two biggest things you can do to help you body adjust include drinking lots of liquids (4-5 liters a day) and going slowly. On Kilimanjaro you’ll repeatedly hear “polepole” (slowly). If symptoms persist or get worse the best solution is to descend. American mountaineer Ed Viesturs always says “the summit is optional, coming home safely isn’t.”
Many climbers also consider using Diamox to counteract altitude sickness. If you don’t have a lot of experience with altitude, you may also want to get a prescription from your doctor for this, even if you don’t intend to take it. It’s better to be safe than sorry. If you decide to take Diamox, it is better to start the day before you climb. Diamox is a diuretic and can make it hard for you to keep hydrated if you don’t start until you’re already climbing.
Most people tend to feel the effects of the altitude at 15,000 ft. or higher. You might feel nauseous or have a splitting headache. One of the easiest and best prevention for altitude sickness is to be properly hydrated.
Most guides recommend drinking at least 1 full litter of water before you even leave your tent in the morning. Then at least 3-4 more throughout the day. Ideally you should have 4-5 litters a day. If you do feel sick, try to rest and take some medication.
On summit day all bets are off. Nobody feels good on the summit. You just have to know how far to push yourself. But remember, the summit isn’t the top of the mountain, it’s getting back safely!