Climbing to the summit of the highest mountain in Africa is definitely a challenge. It is always a benefit to be in good shape, and to enjoy hiking and exercise. You have to be in general good health, and will be required to complete our Medical Assessment Form in order to be allowed to climb.
However the most important factor is how well you acclimatise. If you have never been hiking above 4,500m (14,800 ft), you will most likely not know how well you generally acclimatise. Even if you have done so, there are many factors that can influence acclimatisation. Many of these factors are ones that we can manipulate and thus usually improve your acclimatisation to altitude.
To sum up, if you are in reasonable good health and want to climb Kilimanjaro, ready to take the challenge, you can most likely achieve your goal.