If you take prescription medication—especially if it’s for high blood pressure or heart problems—listen up!

The FDA recently announced a recall of some medications that contain losartan (such as Hyzaar and Cozaar) after tests found contamination with a suspected cancer-causing chemical.

If this sounds familiar, it’s because the FDA has this year announced a series of recalls for valsartan, another drug used by heart patients. A single lot of losartan was recalled because the active ingredient was found to be tainted with N-nitrosodiethylamine (NDEA), an industrial chemical that’s classified as a “probable” human carcinogen. Multiple lots of valsartan have been recalled due to contamination with NDEA or with another “probable” human carcinogen, N-nitrosodimethylamine (NDMA). And lots of the blood pressure drug irbesartan have now also been recalled because of contamination with NDEA.

Not all drug labels include lot numbers, so anyone taking either medication should ask his/her pharmacist if the dispensed generic prescription drug is, in fact, manufactured by one of the companies cited in the recalls. Important: Don’t stop this—or any—medication without checking with your doctor. The risk of stopping a drug cold turkey could be worse than the risk from any possible impurities it contains.

Not an isolated problem: “Unfortunately, this phenomenon is not uncommon,” says Jack E. Fincham, PhD, RPh, a professor of pharmacy administration at Presbyterian College School of Pharmacy in Clinton, South Carolina.

While many drugs have been recalled because of contamination or other problems with manufacturing, some of the largest recalls occurred after popular drugs—such as Baycol (for high cholesterol) in 2001 and Bextra (a painkiller) in 2005—were found to have unexpectedly dangerous side effects.

Self-defense: Ask your pharmacist if the manufacturer listed on your drug label is known to be reputable. If there’s any question about the manufacturer’s track record, you can ask the pharmacist to get your medication from a different manufacturer.

Helpful resource: The FDA website allows you to enter the medication name in the “filter by keyword(s)” field to see if a drug you’re taking has been recalled.

Also: You can sign up on the FDA’s website to receive “Recalls, Market Withdrawals and Safety Alerts.” The e-mails provide the latest recall information about drugs and other FDA-regulated products.

To learn about safety alerts that are available for foods, household products and cars, read here.