IRCT20170513033941N58 IRCT 2019-05-24 National Institute for Medical Research Development of Iran (NIMAD) The effect of thiamine supplementation in the treatment of gestational diabetes The effect of thiamine supplementation on biomarkers of inflammation, oxidative stress and its related gene expression in patients with gestational diabetes 2019-04-24 anticipated 60 Complete https://irct.ir/trial/39531 interventional Randomization: Randomized, Blinding: Double blinded, Placebo: Used, Assignment: Parallel, Purpose: Treatment, Randomization description: To decrease potential confounding effects, all participants will have stratified randomization according to BMI (<25 and ≥25 kg/m2) and age (<30 and ≥30 y). Then, participants in each block will be randomly allocated into two treatment groups to take either supplements or placebo. Randomization will be done by the use of computer software, Blinding description: Randomization and allocation will be concealed from the researchers and participants until the final analyses are completed. Another person at the gynecology and obstetric clinic, who is not involved in the trial and not aware of random sequences, will be assigned the participants to the numbered bottles of capsules. 3 Gestational diabetes mellitus. Intervention 1: Intervention group: 100 mg thiamine (Shafa Pharmaceutical Company, Karaj, Iran) daily for 6 weeks orally. Intervention 2: Control group: Placebo (Barij Essence, Kashan, Iran), daily for 6 weeks orally. Undecided - It is not yet known if there will be a plan to make this available Justification or reason for indecision in sharing IPD is Undecided - It is not yet known if there will be a plan to make this available