Why are some substances that are included in supplements not mentioned in the ingredients list?

Regrettably, some unscrupulous manufacturers include substances in a product without listing them on the label. They do this to make the product work better for the intended purpose without regard to the negative health consequences that also follow. These ingredients are often pharmaceutical drugs known to have serious health concerns and have not been approved for safety reasons. In the case of herbs and other natural products, there could be compounds that are components of such ingredients that are not listed on the label. Though labeling requirements dictate what supplement companies need to include on the ingredient list and supplement facts panel, these standards are not always met.