How do glucose meters measure blood sugar levels?

[Nerdydude101]

So I'm a diabetic and i know about the prickles meters, i want to know how they work though. I would assume it has to do with some form of EM wave possibly reflecting off just the glucose molecules in the bloodstream. Thanks for anything you've got!

 

[UltrafastPED]

Here is a run dowm: http://www.livescience.com/11671-quest-painless-check-blood-sugar.html