Thiamin also known as vitamin B1, is a water-soluble vitamin that is extremely important for obtaining energy from macronutrients, particularly carbohydrate. It carries out much of its functions within the body in a phosphorylated form called thiamin diphosphate (TDP), which is required for function of the pyruvate dehydrogenase complex and Krebs cycle. Thiamin is also required for function of the enzyme transketolase, which assists in the production of ribose from glucose through the hexosemono-phosphate shunt.