High-dose supplements of thiamine prevent the development of microalbuminuria in experimental diabetes. The aim of this pilot study was to assess whether oral supplements of thiamine could reverse microalbuminuria in patients with type 2 diabetes. Type 2 diabetic patients (21 male, 19 female) with microalbuminuria were recruited at the Diabetes Clinic, Sheikh Zayed Hospital, Lahore, Pakistan, and randomised to placebo and treatment arms. Randomisation was by central office in sequentially numbered opaque, sealed envelopes. Participants, caregivers and those assessing the outcomes were blinded to group assignment. Patients were given 3 x 100 mg capsules of thiamine or placebo per day for 3 months with a 2 month follow-up washout period. The primary endpoint was change in urinary albumin excretion (UAE). Other markers of renal and vascular dysfunction and plasma concentrations of thiamine were determined. UAE was decreased in patients receiving thiamine therapy for 3 months with respect to baseline (median -17.7 mg/24 h; p