A recent study suggests that the combination of manganese and DCI is much more effective than either alone in reducing glucose levels. Have a look at the results below:

The blood glucose level was reduced (over two hours) by 21% with DCI alone. With the addition of manganese, the reduction was 47%!

As there is no recommended daily allowance for manganese, we rely on the National Institute of Healths Adequate Intake guidelines for our recommendation of 1.8, 2.0 milligrams per day. Most daily multi-vitamins have an appropriate amount. Check the label to be sure.

Also, please be aware that too much manganese can be harmful. Make sure that you are not getting it from more than one supplement, and if you are do the math. The National Institute of Health advises against more than 11 milligrams per day for adults.

Citations
Larner, J., MC Fonteles, et al. Antihyperglycemic effects of 3-O-methyl-D-chiro-inositol and D-chiro-inositol associated with manganese in streptozotocin diabetic rats. Hormone and Metabolic Research. 32.4 (2004): 129-132. Print. http://www.ncbi.nlm.nih.gov/pubmed/10824707

Manganese. MedlinePlus. U.S. National Library of Medicine, 06 Jan 2012. Web. 14 Aug 2013.

https://ods.od.nih.gov/factsheets/Manganese-Consumer/