Vitamin B1 (Thiamine)

The Vitamin B1 (Thiamine) test, also referred to as thiamine diphosphate (TDP) or aneurin assessment, is used to investigate suspected thiamine deficiency and to appraise B‑vitamin status in populations with elevated risk from poor intake, malnutrition, parenteral nutrition, prior gastric bypass surgery, chronic alcohol use disorder, or malabsorption disorders such as celiac disease. It supports diagnostic evaluation when clinical findings suggest beriberi or Wernicke–Korsakoff syndrome and is employed to track response to nutritional repletion. Testing may be performed as whole‑blood thiamine or TDP quantification and can be complemented by functional assessment (erythrocyte transketolase) when appropriate.

B‑complex vitamins are required in small quantities for metabolic processes and energy generation, and because they are water soluble, excess amounts are excreted in urine. Thiamine serves primarily as thiamine diphosphate, a coenzyme for pathways of glucose and amino acid metabolism, and is necessary for normal neurologic, cardiac, and skeletal muscle function. Common dietary sources include fortified cereals, whole grains, bran breads, potatoes, pork, seafood, nuts, and legumes. Laboratory evaluation can quantify thiamine or thiamine diphosphate in blood, and a functional approach using erythrocyte transketolase activity may also be used. Advanced deficiency manifests as wet beriberi with high‑output cardiac failure or dry beriberi with peripheral neuropathy; thiamine deficiency also underlies Wernicke encephalopathy and Korsakoff syndrome. Deficiency develops from inadequate intake, impaired absorption or utilization, increased physiologic requirements, or antagonism related to diet or coexisting nutrient deficiencies. Groups at highest risk include individuals with malnutrition, chronic alcohol use disorder, malabsorption (eg, celiac disease), those who have undergone gastric bypass, older adults, and persons with chronic disease or prolonged diarrhea; risk also increases during pregnancy when diet is restricted. Toxicity from B‑complex vitamins is uncommon, though excessive intake of some B vitamins can adversely affect hepatic or neurologic function.