Heading 300331 covers insulin-containing medicaments that are NOT put up in measured doses or packaged for retail sale — typically bulk pharmaceutical intermediates or hospital-supply formats. Heading 300431 covers the same active ingredient but in finished dosage form (e.g., vials, cartridges, pens) intended for end-use administration.

Importers must ensure the foreign manufacturing facility is registered with FDA under the Drug Establishment Registration program, that the product has an applicable drug master file or IND/NDA reference, and that the shipment is accompanied by a commercial invoice identifying the active ingredient, concentration, and intended use. FDA may detain shipments for examination if the facility lacks a satisfactory inspection history.