Dietary Supplement Safety Act of 2003

Amends the Federal Food, Drug, and Cosmetic Act to require each manufacturer of a dietary supplement (supplement), and each packer or distributor of a supplement the name of which appears on the labeling, to report serious adverse experiences to the Secretary of Health and Human Services and to investigate such occurrences. Defines a serious adverse experience as an adverse event associated with the use of a supplement in a human that involves death or one of other serious calamities. Directs the Secretary to conduct a clinical evaluation of each such reported experience.

Requires the manufacturer of a dietary supplement to report periodically on other adverse experiences and to review such occurrences.

Allows the Secretary to grant a waiver from the above reporting, reviewing, and investigating requirements with respect to a dietary supplement upon determination that compliance is not necessary to protect the public health.

Authorizes the Secretary to require a manufacturer to conduct postmarket surveillance for a supplement under specified circumstances.

Permits the Secretary to require a manufacturer of a supplement or of an ingredient in a supplement to demonstrate that its product is safe under specified circumstances. Directs the Secretary to approve the continued marketing of such a supplement or ingredient or to disapprove it.

Prohibits any introduction into interstate commerce of a supplement containing a stimulant unless it is approved by the Secretary under this Act.

Amends the Act to exclude a product that bears or contains an anabolic steroid from the definition of a dietary supplement for a specified chapter of the Act.

Eliminates a provision of the Act requiring the United States to bear the burden of proof to show a supplement or an ingredient in a supplement is adulterated due to a safety violation.