Vitamin B1 or thiamine is a water-soluble vitamin and one of the B-vitamin complex; “In human tissues, thiamine occurs mostly in phosphorylated forms as thiamine monophosphate (TMP), thiamine diphosphate (TDP, called also thiamine pyrophosphate), thiamine triphosphate (TTP), as well as its non-phosphorylated form (‘free thiamine’). Free thiamine functions as the precursor for TDP, which acts as a coenzyme for enzymes involved in carbohydrate and branched chain amino acid metabolism, and in energy-yielding reactions. Thiamine deficiency leads to disorders that include several forms of beriberi, with mostly neurological and cardiovascular manifestations” (EFSA NDA et al. 2016). Thiamine requirement can be estimated via erythrocyte transketolase activity.