Dear Dr. Edelman, I love the FreeStyle Libre, but sometimes when I put on a new sensor, the readings are higher than with the previous sensor, even if I didn’t eat anything. Is that normal? Does it make a difference where you put the sensor?
Dr. Edelman: The location on your arms should not matter that much. Wide swings in glucose when you swap out sensors is not uncommon at all, and a lot of folks going on CGM are surprised about that. All sensors can be inaccurate, but you should double check with your glucose meter (yes…prick your finger) to get a comparison. Remember you need to have very clean fingers before testing and there is a thing called the lag time in that if you are going up or down quickly, your finger stick value will lag behind. If you have a sensor that is way off, like over 20% from the finger stick value consistently, call the company to get a replacement sensor for free. Lastly, all sensors are less accurate the first 24 hours after putting on a new one.