The agency said the drugs contained the likely carcinogenic N-nitrosodimethylamine (NDMA) beyond the acceptable limits in their extended-release formulations alone.
NDMA Pollution was responsible for recalling Zantac heartburn medicine sold by Sanofi SA and some generic versions of the treatment last year.
The FDA, which said it would send the company’s recall notices on its website, named Canadian company Apotex Corp as one of the companies whose metformin tablets has high levels of NDMA. It has yet to reveal the names of the four other companies.
However, the agency said patients should continue taking metformin tablets, even after recalls, until they consult their health care professional who may prescribe a replacement.
In December, the FDA had started a study on metformin, which is used as an initial treatment for patients with type 2 diabetes.
Online pharmacy Valisure said in March that its independent testing showed high levels of NDMA in metformin conducted by 11 companies, including Amneal Pharmaceuticals Inc and Aurobindo Pharma Ltd.