ALA is a mixture of two isomers of lipoic acid. One does not work biologically in the body. R-lipoic is an improved cleaned up one that only contains the active part. You can get by with 100mg a day, and it is less $$ (if you buy carefully and use places like iherb). R-lipoic can also improve glucose control, so you need to test your blood for a while to see if your sugars go too low. Adjustments in your insulin may be needed.
R-lipoic is relatively new. There is one study showing ALA may affect thyroid hormone in rats. This has not been shown yet to be true in humans. It is also unknown if r-lipoic has this effect, or if it is due to the other isomer present in the ALA. There is the one study floating around the net with no updated ones.
There are many ALA ones however, showing benefit for diabetics.

The body only uses methyl B12. If you are not methylating properly, due to a genetic error then you will not get as much response from other forms. Poor methylators also can't methylate folic acid. There is activated folic acid called MetaFolin. Since methylcobalamin is so inexpensive it doesn't make sense to use any other kind. It is also relatively new, and not often available locally. That is why many of us use iherb.com

There is a 3rd supplement that diabetics can benefit from and that is benfotiamine. If you search that word here you can find my posts about it.

Diabetics normally lose magnesium thru the urine. They also benefit from inositol supplements. For some reason both are lost in the urine in high amounts daily.

http://www.mgwater.com/diabetes.shtml

http://www.thehealthierlife.co.uk/na...tes-00133.html

A new form of inositol is being used now for type II and I am trialing it. It is supposed to be close in strength to metformin without the side effects. However, now, it is very expensive, so I am not recommending it yet.

http://ezinearticles.com/?D-chiro-In...pe-2&id=474415
Since this article was written, 2 commerical forms have come on the market. Both are about $85 a month.

Regular inositol is very inexpensive as the powder. Jarrow has 8oz of pharmaceutical grade for $11.95. It lasts more than 6mos. My husband and son take it. I find it makes me hyper in the 2 gram range, so I switched over the the chiro form.
But they like it alot. It also has an anti-anxiety effect for them.
You mix it into juice...it has no taste, almost a light sweet taste.
Some doctors use it in diabetics or for those with insulin resistance. You'd need at least one gram a day.