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High-dose thiamine supplementation improves glucose tolerance in hyperglycemic individuals: a randomized, double-blind cross-over trial



To assess the effect of high-dose oral thiamine supplements on glucose tolerance in patients with impaired glucose metabolism.


Twelve hyperglycemic subjects (10 cases of impaired glucose tolerance and 2 new cases of type 2 diabetes) completed this randomized, double-blind trial, where all participants received both placebo and thiamine capsules (3 × 100 mg/day) for 6 weeks in a cross-over manner. The main endpoint was changes in 2-h plasma glucose. Fasting plasma glucose and insulin, 2-h plasma insulin, the hemostatic model assessment of insulin resistance (HOMA-IR), renal function measurement and thiamin status were also evaluated at the commencement and completion of each treatment period.


Thiamine supplementation resulted in significant decrease in 2-h plasma glucose relative to baseline (8.78 ± 2.20 vs. 9.89 ± 2.50 mmol/l, p = 0.004), with no significant change in the placebo arm. Fasting plasma glucose and insulin, and HOMA-IR increased significantly from baseline after 6 weeks in the placebo arm (p = 0.003, p = 0.04 and p = 0.02, respectively). These variables did not change with thiamine supplementation. There were no significant changes in 2-h plasma insulin or renal function marker, within or between arms.


Supplementation with high-dose thiamine may prevent deterioration in fasting glucose and insulin, and improve glucose tolerance in patients with hyperglycemia. High-dose thiamine supplementation may prevent or slow the progression of hyperglycemia toward diabetes mellitus in individuals with impaired glucose regulation.

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Fig. 1



Estimated glomerular filtration rate


Impaired glucose tolerance


Glutaminefructose-6-phosphate amidotransferase


Red blood cell


Thiamine pyrophosphate


Thiamine-responsive megaloblastic anemia


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This study was funded by an intramural grant.

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Correspondence to F. Alaei Shahmiri.

Additional information

Trial registration: Australian New Zealand Clinical Trials Registry ACTRN12611000051943.

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Alaei Shahmiri, F., Soares, M.J., Zhao, Y. et al. High-dose thiamine supplementation improves glucose tolerance in hyperglycemic individuals: a randomized, double-blind cross-over trial. Eur J Nutr 52, 1821–1824 (2013).

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  • Thiamine
  • Glucose tolerance
  • Insulin resistance
  • Hyperglycemia
  • Type 2 diabetes
  • Cardiovascular disease