The US Food and Drug Administration (FDA) is investigating if the popular type-2 diabetes drug Metformin is possibly contaminated the same carcinogen that led to the heartburn drug Zantac being pulled off shelves this year.

It's part of a broader push to determine how many drugs might contain the carcinogen, known as N-nitrosodimethylamine (NDMA).  The US is reacting to findings in Singapore of NDMA impurity in some Metformin products.  Europe's drugs watchdog EMA is also asking companies to test Metformin medicines in the European Union for NDMA.

"While we are aware that some regulatory agencies outside the US may be recalling some Metformin drugs, there are no Metformin recalls affecting the US market at this time," said Dr. Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research.  "The FDA is investigating whether Metformin in the US market contains NDMA, and whether it is above the acceptable daily intake limit of 96 nanograms," she added.

For now, the US FDA is recommending type-2 diabetes patients continue taking Metformin because "there are no alternative medications that treat this condition in the same way".

The presence of NDMA in blood pressure and heartburn medications - including Zantac - prompted full recalls in the last year and a half, especially in Australia.