The topic keeps coming up in the forum, as there is the expected amount of hype surrounding a multi-billion $ product that people have been trying to make for decades. So of course an Arduino+$10 sensor will do the trick!
Hence, this open source research editorial in the Journal of Diabetes Science and Technology is worth a read:
Recall that Elizabeth Holmes and Theranos had a fantastic $9B scam going with blood monitoring, and they lived the high life until someone spilled the beans. She should be out of jail in about eight years.