National Drug Code (NDC) codes are assigned to each medication listed under Section 510 of the US Federal Food, Drugs, and Cosmetics Act, and exist in one of the following groupings of digits into segments: 4-4-2, 5-3-2, 5-4-1, 6-3-2, or 6-4-1 with certain structure rules that apply depending on the length of certain segments while keeping in mind that based on new FDA validation procedures an NDC code assigned to one product is unique and cannot be later reassigned to a different product.
The National Drug Code (NDC) is a unique product identifier used in the United States for drugs intended for human use. NDC codes exist in one of the following groupings of digits into segments: 4-4-2, 5-3-2, 5-4-1, 6-3-2, or 6-4-1. The following NDC structure rules apply depending on the length of certain segments. The National Drug Code is a unique 10 or 11 digit, 3-segment numeric identifier assigned to each medication listed under Section 510 of the US Federal Food, Drug, and Cosmetic Act. While in the past labelers may have had the opportunity to reassign old product codes no longer used to new products, according to the new FDA validation procedures, once an NDC code is assigned to one product (defined by key properties including active ingredients, strength, and dosage form) it may not be later reassigned to a different product. 
