The main circulating form of vitamin B₁ is thiamine diphosphate (TDP) which is found almost completely in red blood cells. TDP is a cofactor for several enzymes – pyruvate dehydrogenase and transketolase (activity is sometimes measured as an indicator of vitamin B₁ deficiency) and thiamine triphosphate is thought to be important in nerve conduction.

Deficiency is most commonly associated with low intake (poor nutritional status – eg. in alcoholics, elderly), severe protracted vomiting. increased requirements (exertion, pregnancy, fever, breast feeding and rapid adolescent growth, TPN) or increased loss (haemodialysis). Deficiency can result in peripheral neuropathy, encephalopathy, muscle pain and tenderness, and congestive cardiac failure. The encephalopathy known as Wernicke Korsakoff syndrome, consists of abnormal eye movement and gait, confusion and memory loss.

Most vitamin B₁ in transported in blood in association with red blood cells and so assessment of possible deficiency is by measuring levels of TDP in whole blood.

Sample Requirements and Reference Ranges for Vitamin B₁

* This is the absolute minimum volume; these volumes are insufficient to carry out a repeat analysis in the event of an analytical problem.