Although this is an informative article, it shows most of my prescription meds are contraindicated, and I think they are over zealous in this. I do not consider Livestrong as a primary source of info, and treat their info with suspicion.
The possibility of BM lowering bgl is known, which is exactly why we take it as a supplement. So it is doing what is claimed? Yeah! another tool to use. Along with most of the others mentioned (which by the way we get from eating leafy greens anyway). The warning about lactic acidosis is covered in the meds leaflet anway and has nothing to do with taking supps - Metformin does that on its own in rare occasions.
We should indeed let our HCP's be aware of supplements if taken. My GP and DCN are both quite interested in my own success with these, so not all doctors are against self medication. Met by itself is not that good at bgl lowering, and usually requires supplementation by other prescrip meds.