Metformin Contaminated With Cancer-Causing Chemicals NDMA in Other Countries, Sparking FDA Investigation

Following the discovery of cancer-causing chemicals in metformin sold outside the U.S., federal regulators indicate that they are investigating whether the generic diabetes drug may contain the same carcinogenic byproducts that have resulted in widespread valsartan recalls and Zantac recalls over the past year.

In an FDA statement issued on Thursday, the regulatory agency announced that it is investigating the presence of N-Nitrosodimethylamine (NDMA) and similar chemicals, known collectively as nitrosamines, in metformin, after the impurity was found versions of the diabetes drug sold in other countries.

To date, the FDA indicates it has not found excessive levels of NDMA in metformin sold in the U.S., but the chemical has been linked to reports of stomach cancer, colorectal cancer, liver cancer and other cancers along the digestive tract after contaminating other medications in recent months.

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Zantac Lawsuits

Side effects of Zantac may increase the risk of cancer, due to chemical impurities found in the heartburn drug.


NDMA is a chemical byproduct, which is considered a carcinogen. It used to result from making rocket fuel in the early 1900s, but today is only used in laboratory experiments to induce cancer in animal test subjects.

Metformin is a commonly drug used as a front-line treatment for type 2 diabetes. It is sold under several brand names, including Glucophage, Carbophage, Fortamet, Diabex and Riomet. It is also often used in combination with other diabetes drugs, and is widely used worldwide.

Recent findings by the Singapore Health Sciences Authority led to a metformin recall for three products, out of 46 tested. Following those results, the FDA, the European Medicines Agency, and Health Canada have all launched investigations. However, no additional recalls or have been issued at this time.

“While we are aware that some regulatory agencies outside the U.S. may be recalling some metformin drugs, there are no metformin recalls affecting the U.S. market at this time. The FDA is investigating whether metformin in the U.S. market contains NDMA, and whether it is above the acceptable daily intake limit of 96 nanograms,” Dr. Janet Woodcock, director of the FDA’s Center for Drug Evaluation and Research, said in the press release. “The agency will also work with companies to test samples of metformin sold in the U.S. and will recommend recalls as appropriate if high levels of NDMA are found.”

Valsartan and Zantac Recalls

Concerns over NDMA contamination began last year with an investigation into number of blood pressure drugs. This led to several rounds of valsartan recalls, as well as recalls for losartan and irbesartan. The NDMA in those drugs is believed to be a by-product of changes in the generic drug manufacturing processes.

In response to concerns about the cancer risk with valsartan, and the possibility of shortages for the hypertension drug, the FDA established a permissible daily limit for NDMA at 96 nanograms, requiring pills that may expose users to more of the carcinogen to be recalled.

As a result of these concerns, new testing procedures were initiated by an independent pharmacy, which discovered earlier this year that most versions of the heartburn drug Zantac also contain alarming levels of NDMA. This has resulted in Zantac recalls for most brand-name and generic versions of the drug, which may expose users to levels of NDMA that are substantially higher than permissible daily intake levels established by the FDA.

Unlike valsartan, where NDMA contaminated the pill due to the manufacturing process, it appears that NDMA in Zantac was caused by the instability of the active pharmaceutical ingredient, which may produce NDMA when exposed to high temperatures, such as during transit or inside the human body.

While drug makers and federal regulators indicate they are continuing to investigate the underlying cause of both the NDMA contamination, many consumers diagnosed with cancer in recent years are now pursuing valsartan lawsuits and Zantac lawsuits, alleging they may have avoided a cancer diagnosis if other treatments had been used.


  • LARRYFebruary 8, 2023 at 12:48 pm

    was walking, no problems started taking metformin 8yrs ago at age 70th cant walk was not overweight. my problems started one after taking it had to be taken off it. 82nd airborne vet.

  • JerroldMarch 10, 2022 at 7:25 pm

    63 y/Old male taking metformin XR for years through the VA. Actively being tested for liver problems fatty liver, with extremely highly fibro liver, signs of cirrhosis and swollen lymph nodes surrounding the liver from MRI, fibroscan scale / 1400.

  • BrendaJuly 7, 2020 at 10:22 pm

    I've been taking metformin for over 20 yrs. And things are starting to go wrong with me.

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