Couldn't agree more with SussexDave. Check after using the sensor if you see it indicating up or down as its reading will not give you the true level you need. It is an amazing device to let you know the direction of your blood sugar levels. My own levels have improved greatly and it was a bit of a shock to see the pattern during twenty four hours. My daily routine has changed a lot since I have been wearing the sensor. I used to get high readings in the morning but after advice from my GP I now inject 15-20 before my breakfast and I have managed to stay within the blue sometimes all day. I would like to add this always consult your doctor/nurse before doing this and do it gradually. Remember we are all very different.
Finally I would like to add I am currently suffering with Bronchitis and my seensor has indicated very high levels of up to 22.5 and they still remain high after 6 days. Finger pricking also indicates high levels as well, of up to 20.00! This shows a reasonable consistency so for me the Libre system is invaluable as I think I would have needed a blood transfusion by now if I hadn't had it.
Every time I get an infection this happens but it does come down eventually so don't despair its your average that counts over a month. Hypos are the real worry as they seriously bad news. I have had the big D now for 45+ years (currently 74) and believe me those early days were really difficult, which I describe like it was driving a car with a bowl of hot soup in your lap.