Why is my Mac using so much memory?
Dont worry about the inactive part, this doesnt mean that your mac
  will run slow, macintosh keeps these inactive(as IDLE) where when
  programs needed*-(the ones that you've been using)-* then accessing
  them would be faster since they are still in a way or another in
  memory regardless of swapping being in process.
  
  And if your scared of the inactive blue color eating the pie chart
  displayed, then open your terminal and type: "purge" to clear your
  inactive space.