Type 2 diabetic patients undergoing twice daily injections of premixed insulin are administered glinides (10mg of mitiglinide or 90 mg of nateglinide) at lunchtime without changing their insulin regimen. Twelve weeks after administration of the glinides, they are discontinued. HbA1c levels at the start of glinide administration, 12 weeks after administration, and 12 weeks after discontinuation are measured.