Your ability to acclimatize depends on the level of oxygenation of your vital organs, most importantly the brain. Since oxygen levels are decreasing as we ascend, the only ways to adjust are to 1./ increase respiration or 2. / to change the blood chemistry so that it can accommodate more oxygen (by an increase of red blood cells).
The latter will occur naturally as you spend time at altitude, and guidelines from experts in this science recommend an ascent of no more than 2,000 feet (610 M) per day, with one day of rest every third day. That translates roughly into 4,000 feet (1,220 M) every three days. Ideally, when you reach your high camp, you should not be too far in deficit, in order to give you the best chance to safely reach the summit the next morning.
The most commonly used high camps (Barafu Camp and Kibo Hut Camp) are situated at about 4,700m, so if at the start of your trek you are acclimated to the elevation in Arusha (1,400m), the objective would be to be able to acclimatize to 4,700m (a difference of 3,300m). In order to follow the above guidelines, you would need to plan 8 days to reach Barafu Camp and be well acclimatized. That means a 9 or 10 day trek. This is why summit success rates are so much higher for 9 and 10 day treks. Shorter treks are more challenging from an acclimatization standpoint, so we often have to take remedies to address that. A very common remedy is the medicine called acetazolamide, commonly known as ‘Diamox’. See the FAQ on ‘Diamox’
