The title of this topic is the title of a brand new scientific article just e-published before print. You can read the full text here: http://www.sciencedirect.com/science/article/pii/S2352396417303341
It is a follow-up article to a previous report (2 years ago) suggesting that the long-term complications of diabetes (i.e. blindness, numbness in the feet, kidney failure, and cardiovascular disease) are the result of vitamin C deficiency in the red blood cells. Specifically it implicates diminished transport of the oxidized form of vitamin C, dehydroascorbic acid (DHAA), into the red blood cells due to high blood glucose levels. That article's full text can be read here: http://www.sciencedirect.com/science/article/pii/S235239641530164X
The new article describes a new and different experimental technique, the results of which further support the original article's premise. And even further, this new article implicates this diminished transport of DHAA into red cells as the factor which causes low plasma vitamin C levels in diabetics.