Hundreds of thousands of Americans stand to soon lose their access to cheaper weight-loss drugs, with a federal crackdown on copycat versions threatening to disrupt treatment and raise costs.

The Food and Drug Administration has ordered producers and sellers of the less-expensive products to wind down operations in the coming weeks now that it has declared there are no longer shortages of the blockbuster drugs Wegovy and Zepbound.

Produced through a process of mixing drug ingredients known as compounding, the copycat medications had spawned a booming multibillion-dollar industry. Patients turned to compounding because their health insurance would not pay for the brand-name drugs, and they could buy the compounded versions for less than $200 a month in some cases.

Eli Lilly and Novo Nordisk now offer the brand-name drugs for $500 a month in most cases to patients who pay with their own money instead of going through insurance. Until recently, patients sometimes had to pay over $1,300 a month.

The FDA ordered compounding for versions of Eli Lilly’s Zepbound to end last month. Small compounders have until April 22 to stop making and selling versions of Novo Nordisk’s Wegovy; large compounders have until May 22.

It is not clear how the FDA will enforce these deadlines.

Robert F. Kennedy Jr., the health secretary, has criticized the weight-loss medications, saying that people would be better off eating healthful food, though he said last week that they were “extraordinary drugs.” He has not weighed in on the cheaper copycats.

The compounding industry has been waging a public-relations campaign and fighting in court to reverse the orders but has been unsuccessful so far. Some providers plan to keep offering the drugs at dosages that aren’t standard or by mixing in vitamins, moves they hope will allow them to skirt the crackdown.

“We’re about to see just how creative the compounding industry can get,” said Lindsay Allen, a health economist at Northwestern University.

If these strategies keep compounding going even at a reduced scale, it could siphon billions of dollars of business away from Novo Nordisk and Eli Lilly. Drugmakers view these tactics as an illegal attempt to bypass their patents.

In a long-overlooked corner of pharmacy, compounding obesity drugs has generated huge business for telehealth companies and medical spas that connect patients with prescribers. Compounders have supplied not only patients with obesity, but also those with diabetes who couldn’t find the brand-name drugs because of the shortages.

A trade group for large compounders estimates that millions of patients are getting the weight-loss drugs through compounding, which, if accurate, would rival sales of the brand-name products. No one is tracking the specific number of patients getting the drugs this way.

With the FDA’s deadlines, people who can no longer afford the drugs and stop taking them face the prospect of regaining weight and reversing progress in combating other health issues.

In Woodbury, New York, one pharmacy, Town Total Compounding Center, has been supplying the drugs for about 400 patients, charging as little as $210 for a month’s supply. To comply with the FDA’s deadlines, it recently stopped selling versions of Eli Lilly’s product and plans to soon discontinue selling versions of Novo Nordisk’s product.

In Jefferson Township, New Jersey, Victoria Weyand, 66, paid $200 a month for compounded drugs for obesity that were produced by her local pharmacy. She is on Medicare, which generally will not pay for Wegovy or Zepbound. The Trump administration recently rejected a Biden administration proposal that would have expanded Medicare coverage of those drugs for millions of people.

Weyand said she had lost about 25 pounds since starting the drugs last November. But she ran out of her supply of the compounded version of Zepbound earlier this month, and her pharmacy stopped offering it to comply with the FDA’s order. She said she mainly relies on Social Security and won’t be able to afford the extra $300 a month to switch to the brand-name drug. “I don’t know what I’m going to do now. I’m very upset. I feel lost,” she said.