Diabetes drugs are once more under the microscope because the Food and Drug Administration (FDA) has found certain samples of sitagliptin contain nitrosamine – a possible cancer-causing ingredient – at levels above what’s allowable by the agency.

Sitagliptin is used for the management of high blood sugar in individuals which have Type 2 diabetes, however it just isn’t the primary ingredient to boost a flag with the FDA over allowable levels that would cause cancer.

Several makes of the diabetes drugs metformin were previously recalled under the agency’s supervision, in addition to a variety of hypertension pills and Pfizer’s smoking cessation medication – Chantix – all resulting from a possible cancer-causing risk from an ingredient often known as NDMA or N-Nitrosodimethylamine in levels higher than were allowed by the FDA.

Now Merck’s diabetes drugs Januvia, Janumet, and Steglujan, which contain sitagliptin with higher than allowable levels of nitrosamine, are being reviewed by the agency. The pills are still being permitted to be made to stave off a shortage of medication, Bloomberg reported.

In an email to the news outlet, Merck confirmed that it “recently detected a nitrosamine identified as NTTP in some batches of our sitagliptin-containing medicines,” adding that it’s working with health officials globally to place in place quality control measures to make sure the drugs meet FDA interim limits.

The FDA said that it allows 37 nanograms per day of nitrosamine in a drug, but to avoid any shortages of the diabetes medications, it’s allowing as much as 246.7 nanograms each day. The agency did maintain that cancer risk with the allowable increase is minimal.

The FDA said, “It might be dangerous for patients with this condition to stop taking their sitagliptin without first talking to their health care skilled.” It also “recommends prescribers proceed to make use of sitagliptin when clinically appropriate to forestall a niche in patient treatment.”

Januvia is the third best-selling drug for Merck, followed by Janumet, with revenues of $3.3 billion and nearly $2 billion, respectively, in 2021 for the corporate, Bloomberg said.