High Levels of Carcinogen NDMA Found in Common Diabetes Medication


Online pharmacy Valisure has found high levels of N-Nitrosodimethylamine (NDMA), a probable human carcinogen, in batches of metformin from 11 out of 22 tested manufacturers.1

Online pharmacy Valisure has found high levels of N-Nitrosodimethylamine (NDMA), a probable human carcinogen, in batches of metformin from 11 out of 22 tested manufacturers.1

Metformin is a commonly-prescribed medication used to control high blood sugar in patients with type 2 diabetes. It is the fourth most-prescribed drug in the United States, with approximately 80 million prescriptions written in 2019.1

NDMA has been studied since the 1960s and has been confirmed as a possible cause of cancer at high levels. The World Health Organization and the International Agency for Research on Cancer have classified it as a Group 2A compound, meaning it is "probably carcinogenic to humans."2

Valisure analyzed 22 companies selling the drug and a total of 38 batches. In total, 11 companies and 16 batches were found to have NDMA levels above the 96 nanograms, which are considered the acceptable daily limit by the FDA.1 They also found significant variability, even within a single company.1

The company was first alerted to the potential contamination by an individual client, who requested testing for a sample of metformin. After original findings of higher-than-normal NDMA levels in a single batch, the researchers expanded their analysis.1

"We found this was not an isolated incident and that there are many batches that contain unacceptable levels of NDMA," said Kaury Kucera, PhD, chief scientific officer at Valisure, in a statement. "These findings underscore the importance of chemically validating all batches of medications for safety and quality."1

Valisure also sent samples from a contaminated batch to be independently verified by Emery Pharma, and FDA-registered independent laboratory in California. Researchers there confirmed Valisure's findings.1

In response, the analysts filed a Citizen Petition with the FDA on March 2, 2020, urging the administration to request recalls for the identified lots of metformin in accordance with the FDA's mandate to ensure a safe drug supply.1

"The presence of this carcinogen in metformin where multiple tablets can be taken daily and often for a lifetime diabetic condition makes this finding particularly concerning," said Deanna Akinbajo, PharmD, MPH, chief pharmacist at Valisure, in a statement. "Furthermore, the increased prevalence of diabetes in adolescents and young adults strongly underscores the need for quick action to protect patients."1

This newest finding follows NDMA contamination in multiple angiotensin receptor blockers and ranitidine, all of which is increasing concerns from consumers and health care providers.


  • Valisure Detects High Levels of NDMA in Metformin [news release]. New Haven, CT; March 2, 2020. https://www.valisure.com/blog/valisure-news/valisure-detects-high-levels-of-ndma-in-metformin/. Accessed March 4, 2020.
  • N-Nitrosodimethylamine (NDMA). World Health Organization; 2008. https://www.who.int/water_sanitation_health/dwq/chemicals/ndmasummary_2ndadd.pdf. Accessed March 4, 2020.

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