I Have Diabetes (not On Insulin). I Take 1000 Mg

I have diabetes (not on insulin). I take 1000 mg of metformin a.m. and 1000 p.m. Just added 4mg tab glimepiride (one before breakfast and one before dinner) about 3 weeks ago. Today I felt faint, legs weak, shaky, thought I was going to pass out. Blood sugar was 66. Is that considered low? I usually run so high, I'm not used to having a low blood sugar. I ate two powdered donuts and it is up to 84. Feeling better now. Just a little weak.