Objective To measure the vitamin B1 levels in plasma,erythrocytes and urine of the patients with type 2 diabetes,and to analyze the correlation of vitamin B1 level with the progression of diabetic nephropathy,and to clarify the metabolism of nutrtion mechanism of type 2 diabetic nephropathy.Methods Total 90 patients with type 2 diabetes and 30 healthy volunteers were recruited.According to the levels of microalbuminuria,the patients with type 2 diabetes were divided into non diabetic nephropathy (NDN)group,early diabetic nephropathy (EDN)group and clinical diabetic nephropathy (CDN)group (n=30);the healthy people was used as normal control (NC) group.The vitamin B1 levels in the plasma,erythrocytes and urine were examined with high performance liquid chromatography (HPLC). The correlation of microalbuminuria with the plasma viamin B1 level was analyzed. Results The level of vitamin B1 in plasma of the patients in NC group was (7.1±3.3)μg·L-1,while it was (4.0±2.3)μg·L-1 in NDN group,(3.1±1.0)μg·L-1 in EDN group and (2.3±0.6)μg·L-1 in CDN group. Compared with NC group,the vitamin B1 levels in the plasma in NDN,EDN and CDN groups dropped 43.7%, 56.3%,and 67.6%,respectively (P<0.05). The excretion of vitamin B1 in urine were (2.9 ± 0.8),(9.0 ± 4.7),(11.7±3.9),and (15.6±5.0)μg·L-1 in NC group,NDN group,EDN group and CDN group, respectively.Compared with NC group,the vitamin B1 levels in the urine in NDN,EDN and CDN groups were increased by 2,3 and 4 times,respectively (P<0.05).A negative correlation was found between the level of microalbuminuria and the level of vitamin B1 in plasma (r=-0.62,P=0.013).Conclusion Vitamin B1 deficiency can be observed in the early stage of diabetic nephropathy,and the level of vitamin B1 is closely correlated with the progression of diabetic nephropathy.