I am curious about the accuracy of the blood glucose meter.

I have some questions about diabetes. As I get older, my blood sugar levels keep rising, so I am very concerned about my blood sugar. Therefore, I bought a home blood glucose meter to measure my fasting blood sugar. However, the readings are very inconsistent. One day, I measured and got 130, so I was worried and was told to measure again, so I drew blood and checked again. This time, I got 105. How can the same blood from the same body at the same time have such different blood sugar levels?