Finger prick blood glucose readings and sensor glucose reading won't always match and in fact are likely to be different. That's because sensor glucose readings come from the interstitial fluid (ISF), a thin layer of fluid that surrounds the cells of the tissues below your skin, not from your blood.

How big is the FreeStyle Libre 14 day continuous glucose monitor sensor?The sensor is 5 mm in height and 35 mm in diameter and has a thickness of 2 quarters.1 1 Data on file. Abbott Diabetes Care Were there any skin reactions reported by patients wearing FreeStyle Libre