A derivative is classified here only if it is 'used primarily as a vitamin.' If the compound's principal use is as a pharmaceutical intermediate or a different chemical function, it may fall under a more specific heading in the organic chemicals chapters. The heading text and any applicable chapter notes govern; a binding ruling from CBP is advisable for borderline derivatives.

Intermixtures of vitamins are explicitly covered by 2936, but once a vitamin is formulated into a finished dosage form or put up for retail sale as a medicament, it typically moves to the medicaments headings. The distinction turns on whether the product is a bulk chemical mixture or a finished pharmaceutical preparation.