The only example of an approved antidiabetic drug that was developed from a herbal source with a long history of use for diabetes is the biguanide Metformin from French lilac (Galega officinalis). Clinical data are beginning to emerge that support antidiabetic indications for several other herbs. This viewpoint discusses the state of the evidence for their clinical antidiabetic efficacy. One of the most studied herbs, ginseng (Panax spp.), is used as a model to illustrate the challenges associated with achieving reproducible clinical efficacy. It is concluded that the best evidence for clinical efficacy in diabetes remains for ginseng. But overall insufficient evidence exists to claim a diabetes indication for herbs. The experience with ginseng suggests that although reproducible efficacy may be achieved using an acute postprandial clinical screening model to select an efficacious ginseng batch, dose, and time of administration, there is a need to develop a basis for standardization that ties the composition of herbs to efficacy. In absence of such standardization, the use of herbs in diabetes must be approached cautiously.