To clarify the optimum timing for ingestion of acarbose, a 100 mg dose of this oral hypoglycaemic agent was administered 30 min before, at the beginning, and 15 min after ingestion of a test meal, and the effects of the drug on blood glucose rises were compared with increases observed after a control meal (no drug). Twenty-four patients with Type 2 diabetes were included in a randomized, open, cross-over study. The smallest increases in blood glucose (p < 0.001) occurred when acarbose was taken at the beginning and 15 min after starting the test meal (3.3 ± 1.6 mmol I−1 and 3.3 ± 1.4 mmol I−1). The increase in blood glucose levels when acarbose was taken 30 min before the test meal was significantly higher (4.2 ± 1.8 mmol I−1) and it was at its maximum following the control meal (5.2 ± 1.7 mmol I−1). Similar results were observed when the effects of acarbose on insulin and C-peptide levels were measured. It is recommended that patients should be instructed to take acarbose with their first mouthful of food.