No. You do not need new medical evidence. If you have some, send it. But it is rarely worth waiting for some (you can always send it in later). Plenty of people win mandatory reconsideration and appeals without new medical evidence. 

For all our advice on how to give yourself the best chance of a successful MR see Challenging a work capability assessment decision. Please use our free WCA mandatory reconsideration letter tool as research suggests it more than doubles your chances of success at this stage.