21 CFR §111.83

1. (a)You must collect and hold reserve samples of each lot of packaged and labeled dietary supplements that you distribute.
2. (b)The reserve samples must:
   1. (1)Be held using the same container-closure system in which the packaged and labeled dietary supplement is distributed, or if distributing dietary supplements to be packaged and labeled, using a container-closure system that provides essentially the same characteristics to protect against contamination or deterioration as the one in which it is distributed for packaging and labeling elsewhere;
   2. (2)Be identified with the batch, lot, or control number;
   3. (3)Be retained for 1 year past the shelf life date (if shelf life dating is used), or for 2 years from the date of distribution of the last batch of dietary supplements associated with the reserve sample, for use in appropriate investigations; and
   4. (4)Consist of at least twice the quantity necessary for all tests or examinations to determine whether or not the dietary supplement meets product specifications.