Diabetes Self-Management Blog

A combination of insulin and vitamin C may help stop diabetes-induced blood vessel damage in people with poor blood glucose control, according to new research published in The Journal of Clinical Endocrinology and Metabolism. Halting this damage could help prevent a host of complications, such as chronic heart failure, kidney disease, and eye disease.

The investigators looked at 10 people without diabetes and three subgroups of 10 people with Type 1 diabetes who had either been diagnosed within the month or who had been managing their diabetes for roughly five years. Those who had been diagnosed five years earlier were further categorized based on whether their average HbA1c level had been less than or equal to 7% since diagnosis or more than 7% since diagnosis.

Each of the study participants was treated with a combination of insulin and vitamin C in various combinations over the course of 24 hours. In the people who’d had diabetes for roughly five years and an average HbA1c of more than 7%, neither the insulin nor the vitamin C alone had an impact on blood vessel damage. The combination, however, was effective at stopping the damage.

In an earlier study, principal investigator Michael Ihnat, PhD, discovered that cells have a “memory” that allows damage to continue to occur even when blood glucose levels have been brought within target range. The presence of antioxidants such as vitamin C, however, erases this memory and allows cell function to return to normal.

According to Ihnat, “For patients with diabetes, this means simply getting their glucose under control isn’t enough. An antioxidant-based therapy combined with glucose control will give patients more of an advantage and lessen the chance of complications with diabetes.”

While the researchers recommend that people with diabetes eat foods and take multivitamins rich in antioxidants such as vitamin C, they warn that further investigation is needed: Because the vitamin C used in the study was administered at very high doses and directly into the bloodstream, it is unlikely that a person could derive the same benefits from a store-bought supplement. A study is currently under way to investigate the effect of vitamin C and insulin in people with Type 2 diabetes.

To learn more, see the study’s abstract, or read “Stopping Diabetes Damage With Vitamin C.”


  1. What about the absorbtion of it being taken orally? in other words, can you drink alot of homemade lemonade?

    Posted by Gary |
  2. Hi Gary,

    Thanks for your comment. The vitamin C used in the study was administered straight into the bloodstream at very high doses. The researchers suggest that people with diabetes eat foods rich in antioxidants such as vitamin C, but further study will be needed to see what, if any, effect vitamin C taken orally has on blood vessel damage caused by high blood glucose levels.

    Diane Fennell
    Web Editor

    Posted by Diane Fennell |
  3. This would sound good like motherhood and apple pie ( not for diabetics) but I remember reading that the antioxidant vitamins C and E increase insulin resistance which is an issue for many type 1 and all type 2.

    Posted by CalgaryDiabetic |
  4. I cannot say if high doses of vitamin C help to protect against blood vessel damage, or if it might contribute to insulin resistance. I can say, however, that in my experience it helps to boost your immune system. Two years ago I began taking cranberry suppliments which contain an additional high level of vitamin C, with some vitamin E. I took these to help reduce the frequency of urinary track infections. Since then, not only have I not had another UTI, but, have also not had a cold, nor caught any of the viruses that have been prevalent in my area during the winter. I will add that it does not seem to have affected by diabetes control, as my levels have remained relatively constant while taking this supplement.

    Posted by Chris Hood |
  5. Vitamin C increases cardiovascular mortality in post menopausal women with type 2 diabetes at doses as high as 500 mg:

    If any of you reading this have a research background, I would love some feedback. I am now very cautious about my dosages of vitamin C. I am pre diabetic.

    Posted by Idelle |
  6. Thanks for sharing nice and useful information. Its useful to me and my friend who is diabetic patient since childhood.
    Vitamin C helps to stop blood vessel damage caused by the disease in patients with poor glucose control.

    Posted by thé |
  7. Comments ascribing beneficial effects of Vitamin C, in relation to development of diabetes complication, are best treated with skepticism.

    However, insofar as Vitamin C acts as an Aldose Reductase Inhibor, it might contribute toward avoidance of microangiopathies and peripheral neuropathies within insulin-independent cells.

    Posted by Donald Duck |
  8. Since vitamin C is water soluble ( http://www.indepthinfo.com/nutrition/vitamin-c.htm ) it is thought that large doses can be taken safely by people without diabetes. I had not heard or read that it could be an inhibitor for “Aldose Reductase”. Also, I would think that oral consumption would operate as well as taking the vitamin intravenously.

    Posted by Joe Williams |

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