What is a 'proprietary blend?'
A "proprietary blend" is a combination of ingredients used exclusively by one supplement manufacturer. No other company produces the exact same combination of ingredients, and, in most cases, it is difficult to know from the label the exact amounts of each of the ingredients in that blend.
What is the difference between RDA and DV?
Recommended Dietary Allowance (RDA) is the amount of a certain nutrient you should get each day based on your age, gender, and whether you are pregnant or breastfeeding. On a supplement label, you're more likely to see the acronym DV, which stands for Daily Value. This represents how much of a nutrient the supplement provides in regards to a total daily diet. For example, if a calcium supplement is labeled "50% DV," it contains 500 mg of calcium per serving, because the DV for calcium is 1,000 mg per day. Sometimes the DV contained in a supplement will be higher than the RDA for certain people. In many cases, there is no DV for a supplement, so the label will reflect that. Check with your doctor to make sure your supplement doesn't contain too much of any nutrient.
What should I do if I have a side effect from a supplement?
Report any side effects to your doctor, and to the FDA, as soon as possible. You can reach the FDA at (800) FDA-1088, or go to www.fda.gov/medwatch to report a problem.