Need is an interesting word. I’m in the first 4 hours of wearing a Dexcom G6. I might do a few sticks over the next 7-10 days to see if both thermometers are giving me the same “temperature” but I do not care. I do not expect my fellow Americans to pay for two thermometers in my house which may or may not be calibrated. The trend & volatility of each is more important than in absolute measurement.