If you have type 2 diabetes and take the extended-release (ER) form of metformin to help control your blood sugar level, you should know that some metformin ER products continue to be recalled by the U.S. Food and Drug Administration (FDA) due to impurities that may be at higher than acceptable levels.

The impurity in question is N-nitrosodimethylamine (NDMA). It can be found in some foods and beverages, but the National Center for Biotechnology Information said it is also used in research to cause tumors to grow in animals and is “reasonably anticipated to be a human carcinogen” — meaning it can cause cancer. 

In May 2020, the FDA said that it found higher than acceptable levels of NDMA in several lots of metformin ER. The companies that made these lots of metformin ER were asked to voluntarily recall them. The FDA did point out that NDMA had not been found in any metformin immediate-release (IR) products.

The FDA continues to post recalls of metformin ER products, with the latest update coming on Oct. 5. The agency has added 77 lots to the recall list. Medical Daily asked the FDA why the recalls continue almost five months after the FDA first acknowledged that higher than acceptable levels of NDMA had been found in some metformin ER lots.

The FDA responded in an email that they asked all drug companies who make metformin ER to test their “at-risk” products before they were released to the consumer market. If the level of NDMA is shown to be above the FDA acceptable limit, the drug company must notify the FDA and not release the batch to market.




NDMA is used in some manufacturing processes but can chemically form as a byproduct in some drug manufacturing processes. It was the subject of a large recall last year because of its presence in some lots of ranitidine, or Zantac, a medication to treat heartburn. In early 2020, the FDA also recalled some blood pressure medications because of the presence of NDMA. 


The agency said that NDMA can be introduced into a drug product during the process of making the drug, packaging the drug or storing the drug. The FDA denied any current shortage of metformin ER, according to the email sent to Medical Daily

The take home

“Patients taking recalled ER metformin should continue taking it until a doctor or pharmacist gives them a replacement or a different treatment option. It could be dangerous for patients with type 2 diabetes to stop taking their metformin without first talking to their healthcare professional,” wrote the FDA.  

The list of recalled metformin products can be found here.