Used properly, legal dietary supplements are very safe. This doesn’t mean they all work as claimed but there are relatively few serious adverse events associated with use. If you are worried about safety, here is some comforting information: The Townsend Letter, April 2010, reported that according to the most recent information collected by the US National Poison Data System (a 174-page annual report of the American Association of Poison Control Centers, published in the journal Clinical Toxicology), there was not even one death cause by a dietary supplement. Additionally, there were zero deaths from multiple or B vitamins, zero deaths from vitamins A, C, D or E, zero deaths from minerals, and zero deaths from any other vitamin or herbal products. No man, woman or child died from nutritional supplements.
Compare this to a report published in JAMA that said that an estimated 2,216,000 (1,721,000 to 2,711,000) hospitalized patients had serious adverse drug reactions (ADRs) and 106,000 (76,000 to 137,000) had fatal ADRs, making these reactions between the fourth and sixth leading cause of death. And just to clarify, these were patients that received the correct doses of the correct drugs administered by the proper health care professional that still had so many ADR's that it is a leading cause of DEATH!
When choosing to use supplements always look for a full product disclosure that includes potential drug interactions and other contraindications (such as the information published by dotFIT).