it depends on your motherboard maximum memory that can handle most MAC before 2012 only can use 8GB
but here's a useful article that might explain things to you
http://www.cnet.com/news/add-16gb-ram-to-your-macbook-pro/
and What you need to know is adding more memory is 100% safe to your system in worst cases your computer won't recognize the extra memory witch means you wasted money for nothing . But you need to know how to do it first because you might harm the mother board if you touch it with static charges
Hope I Helped