Some tablets should be taken before and some after food. Some tablets even should be taken with the first bite of food, because that is the time they work best. This is very important and you should make this clear from your doctor. If it is before, correct time is around 30 minutes before food.
How do they work?
Different tablets work in different ways. Some stimulate the pancreas to produce more Insulin, some tries to help body"s Insulin to work more efficiently while some others do not allow sugar to be absorbed from the stomach. Few tablets work in more than one way.
Can I combine different tablets together?
Yes, if needed. Generally the rule of thumb is to try the maximum dose or maximum tolerated dose of one group and then combine the second tablet from a different group so that they can work together. But now-a-days we are using combination tablet even from the beginning.