Dr. Friedman uses a supplement is called berberine for prediabetes. Berberine is a Chinese herb that comes from the Coptis chinensis French herb, which has been used in China to treat diabetes for thousands of years. Berberine is available on Amazon or health food stores.
The first drug conventionally used for both diabetes and prediabetes is called metformin. Metformin is a very effective drug and lowers hemoglobin A1c, helps with some weight loss and helps prevent cancers. However, metformin has a lot of gastrointestinal side effects including nausea, diarrhea, bloating, and gas. Dr. Friedman came upon a paper published in the journal Metabolism in 2008 from a Chinese group looking at berberine versus metformin in patients with type 2 diabetes. This paper did find that berberine had a similar effect on controlling A1c, fasting and postprandial blood glucose levels as does metformin. In the second part of this paper, berberine was added on to common diabetes agents including metformin and also was found to lower A1c and fasting and postprandial blood glucose levels when it was added on. In other words, the effects of berberine and metformin were additive.
Dr. Friedman experiences that berberine is quite well tolerated and probably better than metformin and works equally well if not better to lower the hemoglobin A1c in patients with prediabetes or early diabetes and also has the bonus of lowering cholesterol and has some anti-inflammatory and immune supporting properties.