Hello, I understand your concern. This is a very peculiar case indeed and I am sure the doctors have investigated all the possibilities in order to explain it. First of all, high glucose levels in the blood is the definition of diabetes, so yes, in this case, you can safely confirm diabetes. Both metformin and insulin would lead to hypoglycemia (low glucose levels in the blood) in a normal or non diabetic person. In this case it seems blood sugar levels are resistant to treatment and there are only two reasons I can think of. Either the person is taking other drugs that interfere with metformin or insulin effect, such as certain antibiotics, or there is another concomitant condition such as a tumor. In any case, a further investigation is required. I hope this helps. Wishing you all the best