Five classes of oral drugs have been approved for treatment with Type 2 diabetics in the United States:

Sulfonylureas : Enhance insulin secretion from the pancreatic beta cells. Hypoglycemia and weight gain are noted as side effects.

Biguanides: Reduce plasma glucose via inhibition of hepatic glucose production and increase of muscle glucose uptake. Weakness, fatigue, shortness of breath, nausea, dizziness, lactic acidosis and kidney toxicity are noted as side effects.

Alpha-glucosidase Inhibitors: Decrease post-prandial glucose levels by interfering with carbohydrate digestion and delaying gastrointestinal absorption of glucose. Gas, bloating and diarrhea are noted as side effects.

Thiazolidinediones: Improve insulin sensitivity in the muscles and liver. Liver toxicity, weight gain, bloating and hypoglycemia are noted as side effects.

Meglitinides: Augment insulin secretion. Weight gain, bloating and hypoglycemia are noted as side effects.