It is never too late. However, in your 30s you might have more obligations than you did earlier in life. If you have a family and/or mortgage, etc. these will limit your options.
There have been many people who have changed careers late in life, people becoming doctors, authors, musicians, teachers, etc.
If your dream is to make a change, sit down and come up with a realistic plan. Be honest with creating the plan so that you do not give up. It will take work and perseverance, but most people that I know that have switched careers have been ultimately much happier.