The primary objective of this double-blind, placebo-controlled, randomised cross-over study was to investigate the influence of acarbose on insulin requirement in patients with Type 1 diabetes (T1DM) following a standardised meal. In addition, the study assessed the effects of acarbose on post-prandial triglyceride, glucagon and gastrointestinal peptide levels, gastric emptying, and oxidative glucose metabolism. Following normalisation of their blood glucose, 10 patients received a standardised meal together with acarbose (100 mg) or placebo. Each patient was evaluated twice (separated by 10+/-3 days), and the cross-over study design ensured that they received both acarbose and placebo. The insulin requirement for maintenance of normoglycaemia was assessed using a closed-loop insulin infusion system (artificial pancreas, Biostator). Acarbose produced a statistically significant reduction in mean insulin requirement over a 3-hr period following the meal compared with placebo (5171.7+/-2282.6 mU vs 8074.5+/-3045.4 mU; p=0.003). The level of blood glucose control over the same period was similar in the two groups. Gastric inhibitory polypeptide levels also showed a statistically significant decrease with acarbose treatment compared with placebo for AUC (area under the curve; p=0.006) and Cmax (maximum plasma concentration; p=0.022), but not tmax (time to reach Cmax from the start of the standardised meal; p>0.05). Analysis of the other efficacy parameters revealed no statistically significant differences between acarbose treatment and placebo (p>0.05). These results indicate that acarbose decreases insulin requirement in patients with T1DM without affecting gastric emptying.