This hike is only for the healthy and physically fit. However, even for the fit, the possibility of getting altitude sickness is very real. It's best to be already acclimated to altitude (by staying several days in Cuzco or at a similar altitude) to prevent altitude sickness.
Take your time with the ascent. Bring plenty of water, wear hiking clothes and bring extra layers and plenty of sunscreen. Stands along the route sell tea, water and snacks.
Horses, led by locals, can be rented (ascent/descent S60/30), though you will have to do the final ascent on foot. Horses are not allowed because of the steepness of the grade.
Nearby Red Valley (S10, with two checkpoints) is worth the side trip if you have the time.