Thiamine deficiency is assessed by:

Thiamine (vitamin B1) Deficiency It is assessed by Erythrocyte transketolase activity. Thiamine (Vitamin B1) is the marker for transketolase enzyme -which is involved in HMP pathway (in RBCs) Activity of Transketolase is measured (not the quantity). No impoance of checking serum thiamine Riboflavin (Vitamin B2) Deficiency RBC glutathione reductase is the marker for vitamin B2 deficiency. =Enzyme Transaminase activity is checked for Pyridoxine (Vitamin B6) deficiency =If Relation between thiamine and energy is asked then mark enzyme of Link reaction and TCA Because pyruvate dehydrogenase of Link reaction and a keto glutarate dehydrogenase of TCA cycle | give energy and they are requiring vitamins Both link reaction and TCA requires 4 B complex vitamins B1, B2, B3 and B5