A popular diabetes medication is being recalled over an impurity that could cause cancer.

Metformin Hydrochloride Extended-Release Tablets made by Amneal Pharmaceuticals, Marksans Pharma Limited, Teva Pharmaceuticals, and Apotex Corp. are all under recall, according to the U.S. Food and Drug Administration, due to the presence of NDMA, an environmental contaminant that the FDA calls a “probable carcinogen”, in a number of tested lots.

Metformin is typically prescribed for those with Type-2 Diabetes; if your medicine falls under this recall, contact your doctor or pharmacy for advice on what to do next.