The sensor is 5mm in height and 35mm in diameter. The portion of the sensor that gets inserted under the skin is less than 0.4mm wide and it's inserted only about 5mm under the skin. Studies indicate that a vast majority of users found the insertion no more painful than a typical finger prick glucose test1.
1 Most people did not feel any discomfort under the skin while wearing the FreeStyle Libre sensor. In a study conducted by Abbott Diabetes Care, 93.4% of patients surveyed (n=30) strongly agree or agree that while wearing the sensor, they did not feel any discomfort under their skin.
[29 persons have finished the study; 1 person terminated the study after 3 days due to skin irritations in the area where the sensor touched the skin.]