I Am Diabetic For Last 20 Years. My Age Female

I am diabetic for last 20 years. My age Female 80. Oral medication Vildgliopton 50 bd, metformin 500 bd. This apart for heart amlodepine 5 mg and metprolol 12.5. Of late blood sugar jumping to high level fasting 140-160 and after meals upto 200. Diet under control. Have started metformin 1000 bd. What cd be the reason for sudden change and is taking met 1000 correct