OTTAWA – Health Canada is aware that some metformin products available outside Canada have been found to contain a nitrosamine impurity, N-nitrosodimethylamine (NDMA), above the acceptable limit. Metformin is a prescription drug used to control high blood sugar in patients with type 2 diabetes.
At this time, Health Canada is not aware of any metformin products in Canada containing NDMA above acceptable levels. The Department has asked companies to test their metformin products and is collecting samples from companies to conduct its own testing. Health Canada is also working closely with international regulatory partners to inform its assessment of the issue and to determine whether any metformin product in Canada is affected. If a risk to Canadians is identified, the Department will take action as needed and inform Canadians.
Patients should not stop taking their metformin drug without first discussing options with their health care provider. While Health Canada is not aware of any affected products in Canada at this time, it is important to note that the risks from not having adequate diabetes treatment far outweigh any possible effects of exposure to the levels of NDMA found in metformin in other countries. Stopping metformin medication could lead to uncontrolled diabetes, which has serious health risks:
- Immediate symptoms of high blood sugars include increased urination, thirst, excessive hunger, fatigue, blurred vision, drowsiness, irritability, unintended weight loss and dizziness. Very high blood sugars can lead to effects such as vomiting, diarrhea, dehydration, confusion, agitation and coma.
- Longer-term serious health risks include heart disease, nerve problems, kidney damage, blindness and amputations.
NDMA is classified as a probable human carcinogen. We are all exposed to low levels of nitrosamines through a variety of foods (such as smoked and cured meats, dairy products and vegetables), drinking water and air pollution. NDMA is not expected to cause harm when ingested at low levels. A person taking a drug that contains NDMA at or below the acceptable level every day for 70 years is not expected to have an increased risk of cancer.
Health Canada has been working to address the issue of NDMA and other nitrosamine impurities found in certain medications since the summer of 2018. The Department continues to work closely with international regulatory partners to understand the root causes and to address them.