At the summit of Uhuru peak (5896 m, 19344 ft), the atmospheric pressure is less than 50% of the pressure at sea level. This means your lungs only get half as much oxygen with every breath as at sea level.
As you near the summit, every step requires effort, and ignoring the Kilimanjaro guide's matra of "pole pole" (pronounced "poh-lay poh-lay", and meaning "slowly slowly") will leave you gasping for breath.
Most Kilimanjaro climbers will experience some of the symptoms of altitude sickness, which include headache, loss of appetite, nausea, difficulty sleeping. Infrequently, more serious and life-threatening conditions such as pulmonary or cerebral edema (accumulation of fluid in the lungs or brain) may occur. Every year a few climbers on Kili die of altitude related problems.
Unfortunately there is really no way to train for altitude, except to ascend slowly to give your body time to adapt and acclimatize. If you can spend time at altitude in the days and weeks prior to your climb, that's great, but it's not an option for most people. Therefore, it's crucial that you take the time to acclimatize properly on the mountain. Choose one of the longer climbing routes , so that you can spend more time at intermediate altitudes before going for the summit.
A good guide will be trained to recognize altitude problems and immediately evacuate a client with serious problems to lower altitudes. Some of the better tour operators also carry a device called a "pulse oximeter" which measures the heart rate and percentage oxygen saturation in the blood, in order to monitor clients for altitude problems.
You can also reduce the severity of altitude sickness by taking Diamox (acetazolamide) starting a day before and during your climb. Get a prescription from your doctor before you leave home. Diamox helps your body acclimatize, but it's also a diuretic and occasionally causes side effects such as tingling in the fingers and lips, and blurred vision.
The following vaccinations are recommended by the US Center for Disease Control (CDC) for travelers to Tanzania:
You should consult with a physician (preferably one who specializes in travel medicine) to determine which ones are appropriate for you. Be sure to do this several months before leaving
as some of the vaccinations may require multiple shots over a period of time for maximum effectiveness.
Malaria is a serious disease caused by a parasite called Plasmodium, which infects red blood cells. The parasites are transmitted through the bite of a particular type of mosquito. Malaria is a major problem in Africa: the World Health Organization estimates that 1 million people, mostly children in sub-Saharan Africa, die from Malaria each year. You can find more info on malaria at the Center for Disease Control.
Malaria is generally absent at higher elevations (above about 2500 m or 8000 ft), so you will not be at direct risk of malaria during most of your Kilimanjaro climb. However, you are still at risk before and after the climb in Tanzania, especially since as a visitor, you likely have little or no natural immunity to malaria.
There is currently no approved human vaccine against malaria, so you should take prophylactic medications (anti-malaria pills) and avoid mosquito bites. The two most popular anti-malaria medications are Malarone and doxycycline, which have mild or no side effects for most people. Consult
with a physician (preferably one who specializes in travel medicine) to determine which anti-malarial pill is appropriate for your situation. Make sure you bring the anti-malaria pills with you to Africa, as you can't count on buying them when you arrive.
You can also reduce the risk of malaria by avoiding mosquito bites. Use an insect repellent containing DEET, and make sure you sleep with a bed net or in a tent with working mosquito netting at night.
The chances are pretty good that you'll suffer some kind of gastro-intestinal upset during your trip to Africa. Make sure that you bring an over-the-counter diarrhea medication such as Imodium (loperamide). You should also ask your physician for a prescription for a broad-spectrum antibiotic, such as Cipro (ciprofloxacin) to treat bad cases caused by bacterial infection.
The most important measure for avoiding traveler's diarrhea is proper hygiene. All staff and climbers on your trek should wash their hands after using the toilet, and before handling or eating food. When you're choosing a tour operator, ask what they do to enforce hygiene on the mountain. Make sure that you only drink water that has been boiled or filtered, and only eat fruits and vegetables that have been peeled or thoroughly cooked.