What are the ingredients in Thiamin sourced from? Education Team April 15, 2023 04:58 Updated Follow Ingredient Source Thiamin Synthetic Related articles Does Thiamin contain gluten or grains? What are the possible interactions or side effects of using Thiamin? What is the purpose of each ingredient in Thiamin? What are the ingredients in B Complex Plus sourced from? What does "mcg DFE" mean on my label? Comments 0 comments Article is closed for comments.