These guidelines examined the evidence and presented recommendations for the treatment of type 2 diabetes with oral glucose-lowering drugs. It was concluded that metformin (Glucophage) was suitable for most patients, and that some may require an additional drug.

Type 2 diabetes (T2D) is a progressive disease. T2D may be controlled at first with lifestyle changes, like diet and exercise. However, usually medications to lower glucose levels are needed. If glucose remains high, insulin therapy may be necessary.

Many drugs lower glucose levels in different ways. Different drug types include metformin, thiazolidinediones, sulfonylureas, DPP-4 inhibitors, and SGLT-2 inhibitors. 

The American College of Physicians (ACP) has published their 2017 guidelines on the drug-treatment of T2D. The benefits and risks of glucose-lowering drugs, and combinations of these drugs, were examined.

All drugs examined lowered HbA1c levels (measures average glucose over the last 3 months). Metformin was found to reduce HbA1c levels more than DPP-4 inhibitors (such as sitagliptin). When metformin was used with another drug, all combinations lowered HbA1c more than metformin alone.

The ACP recommends that all patients should be treated with metformin first. If glucose levels are not controlled with metformin, the ACP recommends adding a second type of treatment.

Metformin reduced weight more than all drugs, except SGLT-2 inhibitors (such as dapagliflozin). SGLT-2 inhibitors, either alone or combined with metformin, reduced weight more than metformin alone. Thiazolidinediones (such as pioglitazone) and sulfonylureas (such as glimepiride) were associated with weight gain.

SGLT-2 inhibitors reduced blood pressure more than metformin. A combination of an SGLT-2 inhibitor and metformin reduced blood pressure more than metformin alone, or metformin in combination with other drugs.

Metformin was associated with a lower risk of hypoglycemia (abnormally low blood glucose) than other drugs. Sulfonylureas increased the risk of hypoglycemia. SGLT-2 inhibitors were associated with a higher risk of fungal infections of the genitals (thrush, for example). Thiazolidinediones increased the risk for heart failure. 

The ACP concluded that metformin should be given to patients with T2D who need drugs to reduce their glucose levels. If another drug is needed, they recommended adding a sulfonylurea, thiazolidinedione, an SGLT-2 inhibitor, or DPP-4 inhibitor to metformin treatment. 

The recommendations in these guidelines, are guides only, and may not apply to all patients. They should not replace a physician’s opinion.

The drug chosen should depend on the benefits, risks, and needs of the individual patient. Drug treatment should not replace lifestyle changes, and insulin therapy may still be needed in some patients.