If someone has a fasting glucose of around 135 for 5+ years does this mean they have been an untreated diabetic? is fasting glucose of 135 diabetes?

That is a high fasting glucose but I would want other numbers checked as well. What is the hemoglobin A1C, for example? If that number is still normal, then they may have borderline diabetes and can likely control it with diet and exercise. But, if that number is high, they likely have diabetes and should be checking blood sugars pre-meals and bedtime and should be treated with medicine. Good luck