Cheaper Ozempic alternatives are out there. Be wary of fakes and fraudsters.

The price has people looking at less expensive compounded versions. Compounded drugs are custom versions of medications that are made by special pharmacies. They’re gaining more attention, and not just for weight loss.

Typically, people use compounded drugs because the regular version is in short supply or a patient needs a special formulation. Some compounded drugs also cost less. With weight-loss drugs, they cost a fraction of the more-than-$1,000-a-month price tag for the regular GLP-1s.

There are lots of legitimate, safe compounding pharmacies. However, with weight-loss drugs especially, doctors, medical organizations and even the Food and Drug Administration have warned that people need to be wary of bad actors supplying fake or even dangerous products that could harm their health.

“We don’t know exactly what the compounded products contain, what the actual dose of the active ingredient is, or whether the product has contaminants," says Dr. Katherine H. Saunders, a clinical assistant professor of medicine at Weill Cornell Medicine and co-founder of Intellihealth, a medical obesity-treatment company.

If you opt for a compounded drug, make sure the pharmacy is a legitimate one that is accredited by your state. And if a company claims to be able to sell you a version of a GLP-1 without a prescription, don’t buy it.

The ins and outs of compounding

The use of compound pharmacies for weight-loss drugs is growing for many reasons. In some cases, it’s an attractive option for people whose employer health plans are curbing coverage of weight-loss drugs. And shortages have sometimes made it hard to find the regular versions, too.

“There has been an explosion" in patients asking for compounded GLP-1 drugs, says Dr. Jaime Almandoz, medical director of the Weight Wellness Program and associate professor of internal medicine at UT Southwestern in Dallas.

Many people think drugs coming from compound pharmacies are generic versions and are surprised to learn they aren’t. They also might not contain the same active ingredient as the FDA-approved medications, he adds.

Compound drugs exist in a weird corner of the pharmaceutical world. The FDA allows pharmacies to make their own versions of medications when there are shortages, as there currently are with semaglutide, the active ingredient in Ozempic and Wegovy, and tirzepatide, the main ingredient in Mounjaro and Zepbound.

However, the FDA doesn’t approve the compounded medications, so the agency doesn’t verify their safety and effectiveness. Instead, most of the pharmacies that are making compounded GLP-1 drugs are regulated by state licensing boards.

The FDA has said it has received reports of adverse events after people took compounded semaglutide. The agency also received reports of some compounders using salt forms of semaglutide, which have different active ingredients than the approved drugs.

“Poor compounding practices can result in serious drug-quality problems, such as contamination or a drug that contains too much active ingredient," the FDA says on its website. “This can lead to serious patient injury and death."

Novo Nordisk, which makes Wegovy and Ozempic, has sued businesses, including some compounding pharmacies, selling products claiming to contain semaglutide. Eli Lilly, which makes Zepbound and Mounjaro, has filed suits against businesses to halt the sale of products claiming to contain tirzepatide, including some against compounding pharmacies.

What to look for

Scott Brunner, chief executive of the Alliance for Pharmacy Compounding, which represents about 500 to 600 pharmacies, says it’s important to distinguish between bad actors on the internet selling illicit substances and legitimate compounding pharmacies.

To purchase a drug directly from a compounding pharmacy, you need a prescription. This type of compounding pharmacy is regulated by state licensing boards. (There’s another category of compound-making pharmacies that distribute drugs to hospitals.)

If you buy something marketed as, say, “research-grade semaglutide" online without a prescription, that’s potentially dangerous.

“That’s not a compounded drug and it’s not even a pharmacy," says Brunner.

Injectable compounded versions of GLP-1 drugs can only be made by sterile compounding pharmacies that must adhere to numerous sanitary and compliance standards, says Brunner. And a compounding pharmacy must buy its substances from FDA-registered facilities.

If a doctor prescribes a compounded version of a GLP-1 drug, ask them if they are familiar with the pharmacy. If it’s a legitimate pharmacy it should be licensed in your state. The National Association of Boards of Pharmacy has a list of state boards on its website.

Another thing to look for is accreditation from the Pharmacy Compounding Accreditation Board. The board is part of the Accreditation Commission for Health Care, a nonprofit organization that has accredited more than 3,000 pharmacies, about a third of which currently perform compounding.

Jaime McMinn, a 48-year-old human-resources executive who lives in  Houston, has been taking a compounded weight-loss drug for about six months. She says her insurance wouldn’t cover the regular drugs.

She pays about $295 a month to buy the compounded form from a pharmacy recommended by her doctor. She has lost about 45 pounds.

McMinn says she feels comfortable with sourcing the medication from an accredited compounding pharmacy. “I also had more confidence knowing that my primary-care physician—part of a large medical hospital system here—endorsed this particular pharmacy," she says.

Her husband, Chris White, has coverage to take a GLP-1 drug but is unable to find it currently because of shortages. Unlike his wife, he says he isn’t comfortable buying a compounded version and is waiting until he can find the brand-name drug.

Write to Sumathi Reddy at Sumathi.Reddy@wsj.com