The campaign is being launched before the MS conference in November, and is designed to create awareness of how traumatic MS can be for young people.
The ads focus on the different symptoms that can affect people. The campaign consists of seven wax voodoo dolls with pins stuck in a different part of the body to represent a different symptom for every day of the week.
For example, Monday is immobility and Tuesday is slurring. The tagline "you never know where MS will strike next" conveys that each day is unpredictable for someone with MS.
The campaign will run online and on postcards placed in clubs and bars.
Saatchis will also hold a creative gallery event in conjunction with the MS Society to showcase the work of young artists who suffer from the disease.
Kevin Dundas, the chief executive of Saatchis, said: "This campaign helps to demonstrate the unpredictable nature of MS to a younger generation. Through online messages and postcards, the images will connect with a younger audience."
The ads were written by Anna Toosey and art directed by Michael Long. Digital planning and buying is handled by Zed Media, a division of ZenithOptimedia.