The agency warns that the vials may not have been stored properly and could be dangerous to consumers. The FDA has received multiple reports of patients who suffered unsafe blood sugar levels after using the products.
The FDA issued an alert in June that three lots of Novo Nordisk's Levemir insulin were stolen in North Carolina. Regulators say only about 2 percent of the 190,000 vials have been returned.
Regulators advised patients not to use Levemir insulin from lots: XZF0036, XZF0037, XZF0038.
"Replace it with a vial of Levemir from another lot," the agency said in a statement. "If you must switch to another brand of insulin for any reason, first contact your health care provider because another insulin product may require adjustments in dosing."
The FDA says it continues to investigate the theft.
People with type 2 diabetes have trouble breaking down carbohydrates because their bodies have become resistant to insulin, a protein which occurs naturally in the body and is critical to digesting sugars. Over time, diabetics are at higher risk for heart attacks, kidney problems, blindness and other serious complications.