Metformin and cancer: Information on medication's risk surfaces for diabetics

Denise Titian, July 6, 2020

Metformin is a drug widely used in Canada to treat Type 2 diabetes. With Indigenous people at high-risk for developing diabetes, many are taking Metformin to control blood sugar levels. (Wikimedia Commons photo)

An article about the possible link between the prescription drug Metformin and cancer is raising concerns for diabetes sufferers.

Metformin is a drug widely used in Canada to treat Type 2 diabetes. With Indigenous people at high-risk for developing diabetes, many are taking Metformin to control blood sugar levels.

In December 2019 Health Canada announced that it is aware that some Metformin products available outside the country have been found to contain NDMA (nitrosodimethylamine) above the acceptable limit. 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,” says the Health Canada report.

Back in December Health Canada stated it is not aware of any Metformin products in Canada containing NDMA above acceptable levels. The federal department asked companies to test their Metformin products and have collected 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.

Then in February Diabetes Canada issued an update.

“As a result of its recent product analysis, Ranbaxy Pharmaceuticals Canada Inc. is recalling six lots of its prescription RAN-Metformin drug from the Canadian market due to findings of NDMA. After product testing, two lots had NDMA levels above what is considered acceptable if the drug were to be taken over a lifetime,” states the report.

In addition, Ranbaxy is recalling four other lots of the medication as a precautionary measure because they contain NDMA close to the acceptable limit.

NTC Nurse Navigator Lesley Cerney warned that NDMA, when taken in high levels for a long time, has been associated with cancer.

“What the article didn’t tell you is that the issue only affected a small number of the many brands of Metformin,” she added.

According to Cerney, Canada is among world leaders when it comes to drug safety rules. All lots of Metformin with unsafe levels of the ingredient have been recalled. When any drug is recalled, pharmacists are notified and call all the people who received it.

Rachel Dickens, a diabetes educator and dietician with the NTC, says that she is making inquiries about the local supply of Metformin.

“I called both pharmacies in Tofino to make sure the generic version they dispense is not the one with the compound linked to cancer,” she said.

It turns out that the supplies there are safe.

An employee at Tofino’s Pharmasave assured Dickens that if they had dispensed any of the recalled lots of Metformin they would have called every patient that received it.

Dickens said she is aware of one client in Ahousaht that stopped taking his prescribed Metformin due to concerns about NDMA contamination, but has since been reassured that his medication is safe.

Both Diabetes Canada and Cerney advise clients that it is safe to continue taking Metformin.

“If you have any questions about it, call your pharmacist,” said Cerney.

“There is a lot of misleading health information on the internet and social media,” said Cerney. She urges people to contact her if they have any concerns about something they’ve read.

Lesley Cerney, NTC nurse navigator, can be reached at 250-731-5392. Nurses Catherine Gislason (250-720-5491) or Francine Gascoyne (250-739-9850) are also available for help over the telephone.