Ruth
It isn't only sugars that contribute to blood glucose, in fact for every molecule of table sugar, one molecule of glucose is formed. However with starches( which the medics usually tell you to eat plenty of) 100% of the starch molecule turns to glucose, which might be a factor of thousands. I once made a model of a starch molecule from models of glucose and it went 3 1/2 times around my laboratory( i was a teacher).
Hence you need to control the amount of starch that you eat. Even at maximum dose Metformin can't reduce your sugar by much. Only 1 - 2 mmol.
Are you testing your own blood sugars? If not, get hold of a etester and strips. If your doctor won't let you have them, the suppliers will often give a meteer free, but you have to pay for strips if you can't get a prescription. If this is your situaation, I ccannot recommend Abbott Diabetes Care too highly.
The amount by which you cut your carbs is personal to you. I prefer to go really low, ie <30per day.
If you look around this forum, you'll find loads on contrrolling carbs and how to do it, plus alternatives.
Hana