As with training your dog to do anything, the more you are consistent with praise and reward, the more successful your will be in teaching your dog to alert you when there are changes in your glucose levels.
However, every dog learns at a different pace. Having realistic expectations of what your dog is able to learn in a 6-week course is paramount. Additional training may be recommended based on your own dog's learning curve during these sessions. Dogs trained twice daily for about 10 to 15-minutes a session can begin alerting to changes in glucose levels—both high and low—within the first few months. It takes about 2-3 years of consistent training in order to have the most reliable alert dog.
To sum it up—effective training requires a lifelong dedication to working with your dog consistently in order to ensure it performs to the best of its ability.