Yesterday, my nearly 20 year old son jumped into the car, glanced at his new DexCom to see he was in range and drove off. Pre-DexCom, he did a blood test. My husband and I were appalled he did this. My son's thought was that the DexCom has been spot on the past couple of days and reflects his blood sugar, thus he doesn't need to do a blood test. Any other arguments I could offer to my son so that he performs a blood test prior to driving or is the DexCom a good way to determine the blood sugar?