Hi Maria,
TZD is short for thiazolidinedione, the full name of the glitazone drug family. Bit of a mouthful so this type of medication is often called a glitazone or a TZD. Postprandial means after a meal, preprandial means before a meal. By postprandial numbers, what Trinkwasser was saying is that you should check your blood sugar level after food in order to see what effect your meal has had on your blood sugar. Of course this means that you also need to test before the meal so that you know what the increase has been. A test at 1 hour after eating will show your BS at it's peak level, and 2 hours after it should be back almost to the start point. By doing this test and experimenting with different types of food you will know what types of carbohydrates have what effect on your BS levels, and therefore what you should avoid or have only in small quantities.