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Which Metformin is OK and Which is on the FDA’s Problem List?

The FDA admits that several metformin diabetes formulations are contaminated with a probable carcinogen. Which metformin is OK? How would you know?
Which Metformin is OK and Which is on the FDA’s Problem List...
Metformin pills

Is the FDA facing another scandal? It was not that long ago that the agency was announcing massive recalls of popular “sartan” blood pressure medications such as irbesartan, losartan and valsartan because of nitrosamine contamination. Then, on April Fool’s day, the FDA had to request voluntary recalls of ranitidine (Zantac) because it too was showing up with too much nitrosamine.  Now the FDA is calling for removal of some metformin products. How would you know which metformin is OK?

Millions May be Vulnerable:

Metformin is the most widely prescribed diabetes drug in the world. More than 18 million Americans take it daily to control their blood sugar. Many people are also taking metformin off label under medical supervision to treat polycystic ovary syndrome (PCOS) and as an anti-cancer agent.

A few months ago, Singapore, Canada and Switzerland recalled several metformin products from pharmacy shelves because regulators became aware of contamination with the probable carcinogen NDMA. Now, the FDA is notifying health professionals that metformin from five manufacturers may also be tainted. Those companies include Actavis, Amneal, Apotex, Lupin and Marksans.

At the time of this writing only Amneal and Apotex have announced recalls of their extended-release metformin formulations. Most health professionals and patients do not realize that in the United States the FDA has no authority to issue a mandatory recall due to manufacturing problems. As far as we can tell, the agency does not want this authority, which we find astonishing.

Here is a link to the Amneal announcement about its recall. The NDC (National Drug Code) numbers of the 500 mg pills:



Here are the NDC numbers on the 750 mg pills


The Apotex company announcement lists the 500 mg extended release tablets with NDC number 60505-0260-1 as being recalled.

Good luck finding the NDC or lot number on your metformin label. Not all pharmacies put this information in an easily accessible place on the label. We have had better luck finding a lot number on a can of soup than on a prescription drug label.

Why Is There A Probable Carcinogen in Metformin?

Here is how the FDA explains this problem:

“There are multiple reasons for the presence of NDMA in drugs. The FDA has previously found that the source of NDMA can be related to the drug’s manufacturing process or its chemical structure or even the conditions in which they are stored or packaged. As food and drugs are processed in the body, nitrosamines, including NDMA, can be formed.”

The FDA tries to reassure the public with this statement (May 28, 2020)

“Nitrosamine impurities may increase the risk of cancer if people are exposed to them at above-acceptable levels over long periods of time, but we do not anticipate that shorter-term exposure at levels above the acceptable intake limit would lead to an increase in the risk of cancer.”

Reassured? The trouble with metformin is that millions of people with diabetes have been taking this drug for many years, if not decades. The FDA does not seem to know how long this nitrosamine contamination problem has been going on.

More FDA Misery

The online pharmacy Valisure recently published a report suggesting that it’s not just extended-release metformin products that may be problematic. A number of other metformin formulations may also fail the FDA’s standards. An analysis of samples submitted by consumers found that more than a third exceeded the FDA’s daily acceptable intake limit of NDMA.

Which Metformin is OK?

In its Citizen Petition to the FDA, Valisure listed the following companies as providing undetectable nitrosamine levels: 

AiPing Pharmaceutical, Inc.
American Health Packaging (Zydus)
Ingenus Pharmaceutical, LLC
Major Pharmaceuticals
Megalith Pharmaceuticals, Inc.
Mylan Pharmaceuticals, Inc.
Nostrum Laboratories, Inc.
Oceanside Pharmaceuticals
Sun Pharmaceutical Industries, Inc.
TAGI Pharma, Inc.
Westminster Pharmaceuticals, LLC

A more recent Valisure list can be found at this link

DO NOT Stop Taking Metformin!

Patients should not stop taking their metformin! That’s because controlling blood sugar is critical. People may wish to request a replacement from their pharmacy if their pills are from one of the affected manufacturers.

We wish the FDA would make it easier for physicians, pharmacists and patients by listing on an easy to locate web page which metformin is OK and which should be returned to the pharmacy for replacement. Until that day happens, dear reader, we fear you will have to be proactive. Contact your pharmacist and ask whether your metformin is on the voluntary recall list. If she does not know, ask her to please check.

You may also find our eGuide to Preventing & Treating Diabetes to be of interest.

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.” .
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