Thiazolidinediones (TZDs) are a group of antidiabetic agents that can be used along with exercise and diet to lower glucose (blood sugar) levels in patients with type 2 diabetes. These pills reduce resistance to insulin, a hormone that moves glucose from the bloodstream so the cells can use it for energy.

TZDs are taken once or twice a day. Because they do not affect the production of insulin, they are less likely to trigger episodes of low glucose (hypoglycemia), a side effect of some other antidiabetic agents. Side effects can include edema (swelling) and weight gain. Patients taking TZDs have periodic liver tests and should be monitored for possible heart problems.

The U.S. Food and Drug Administration (FDA) has approved two TZDs - pioglitazone (Actos) and rosiglitazone (Avandia) - and three combination drugs that contain a TZD. In 2007 the FDA strengthened warning labels for TZDs to add new information about risk of heart trouble.