I believe FBS is fasting blood sugar. I agree with the low carb. I don't have high BS but it's usually been borderline at 99. With low carb I've able to maintain it at a constant mid 80's. Carbs directly impact your blood sugar, and the FBS is after a night of sleeping. Think about how high it was before it came down? Alternately looking at the type of carbs being consumed can be helpful as well, some carbs spike blood sugar more than others.