Sensor readings versus blood glucose readings

Hi. I started using CGMS about a month ago, and found that the sensor readings and blood glucose readings were often pretty close. I was using my abdomen initially. But I tried using the sensor on my legs, and started to get big fluctuations in readings between the sensor and blood glucose. Returned the sensor to the abdomen again, and am finding I am still getting big fluctuations. Does anyone have any suggestions for locations that give sensor readings that are closer to blood glucose readings? Feel free to share any tips that can improve this too.