WINNIPEG -- A drug used to control high blood sugar for people with type 2 diabetes has been found to contain carcinogens outside the country, Health Canada said.

In a statement Thursday, Health Canada said it was aware that some metformin products, most commonly sold as a pill or tablet, available outside Canada contain N-nitrosodimethylamine (NDMA) above the appropriate limit.

NDMA is classified as a probable human carcinogen, Health Canada said.

“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,” the statement said.

Health Canada patients should not stop taking the drug until they talk with their health care provider.

“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,” Health Canada said.

“Stopping metformin medication could lead to uncontrolled diabetes, which has serious health risks.”

Health Canada said people who take a drug that contains NDMA at or below the acceptable level every day for 70 years are not expected to be at a higher risk of cancer.

The metformin drug found to contain NDMA had levels above the acceptable limits.

Health Canada said at this point it is not aware of any metformin drugs in Canada containing NDMA above the limits, but it is asking companies to test their products. Health Canada is also collecting samples to do their own tests.

If there is a risk to Canadians identified, Health Canada said it would take the action needed to inform the country.