Here are some important lessons that many people--NON-diabetic people, most with normal blood glucoses or just mildly increased--are learning Oatmeal yields high blood sugars. Even if your fasting blood sugar is 90 mg/dl, a bowl of oatmeal with skim milk, walnuts, and some berries will yield blood sugars of 150-200 mg/dl in many people.
Cheerios yields shocking blood sugars. 200+ mg/dl is not uncommon in non-diabetics. (Diabetics have 250-350 mg/dl.)
Fruits like apples and bananas increase blood sugar to 130 mg/dl or higher.
Odd symptoms, such as mental "fog," fatigue, and a fullness in the head, are often attributable to high blood sugars.
A subset of people with lipoprotein(a) can have wildly increased blood sugars despite their slender build and high aerobic exercise habits.
Once you identify the high blood sugar problem, you can do something about it. The best place to start is to reduce or eliminate the sugar-provoking food.