In general, as an initial drug, the higher the fasting glucose level, the greater the sulfonylurea effect will be. In patients with a pre-treatment glucose level of approximately 200 mg/dl (sulfonylureas typically will reduce glucose by 60-70 mg/dl and HbA_1C by 1.5-2%

Well controlled trials have not shown superiority of one 2^nd generation sulfonylurea over another, nor over any of  the 1^st generation agents.

Approximately 10-20% of patients will exhibit a poor initial response to sulfonylureas (primary failures). While these patients are typically those who have severe fasting hyperglycemia (>280 mg/dl) and reduced fasting C-peptide levels, these tests are not specific enough to help decide on the usefulness of a sulfonylurea for an individual patient.