Abstract: A glucosamine sample is analyzed using an isotope ratio mass spectrometer to determine whether the glucosamine sample is corn-based, e.g., vegetable-based, as opposed to shellfish-based. The isotope ratio mass spectrometer yields an isotopic value for ? 13C that is compared to a reference isotope value for corn, typically about ?12.0%. If there is substantial agreement between the two ratios, then it is known with reasonable certainty that the glucosamine origin is corn and is thus vegetable-based. If there is substantial disagreement between the two ratios, it is known that the glucosamine is not corn-based and is likely shellfish-based. In this fashion, end consumers who cannot consume shellfish-based glucosamine, for reasons of religion or allergy, can purchase glucosamine with greater confidence.