(Bloomberg) -- Eli Lilly & Co.’s weight-loss drug Zepbound is officially in shortage in the US, after mounting complaints by patients, doctors and pharmacists who are having trouble finding the drug.

Two doses of the medicine will be limited in their availability through the end of April, according to a US Food and Drug Administration webpage updated Wednesday. The supply constraint is caused by increased demand, according to the agency. 

Lilly’s shares rose 1.4% as of 11:56 a.m., paring earlier gains. A spokesperson for Lilly didn’t immediately respond to a request for comment. 

In recent weeks, dozens of patients have told Bloomberg News that they’ve been unable to find the drug in local pharmacies. Pharmacists have also confirmed that they’re sometimes unable to order the medicine. 

Read More: Zepbound Patients in Panic Mode as Pharmacies Can’t Get Enough

“A few days ago I called every Walmart pharmacy in the state of New Jersey. I wish I were exaggerating,” said Amanda Cella, who takes Zepbound for obesity. “Then, a few in Philly. Then a bunch of mom and pop pharmacies and a hospital pharmacy. I called around for an entire day, no one I called had the 7.5mg in stock.” The FDA lists that dosage as available, but pharmacy staff across the country have said it’s been on backorder.

When she experienced similar supply issues last year with Novo Nordisk A/S’s Wegovy, a similar weight-loss shot, she had to abruptly stop taking the medicine and quickly started regaining weight, she said. 

Unable to find Novo and Lilly’s drugs, some patients are turning to compounded versions, which the FDA allows to be made during drug shortages. The compounded medicines are made from the same active ingredients and can cost half as much. The FDA doesn’t approve compounded products or have the same oversight it does with traditional prescription drugs.

Obesity shots have skyrocketed in popularity in recent years, making it difficult for the drugmakers to keep up with the intense demand. The companies have said they’re ramping up production, but it’s unclear how quickly that will resolve the problems. Shortly after Zepbound launched, Lilly executives said they would likely not be able to meet 2024 needs.

Lilly’s manufacturing challenges are due to the complexity of making the pen-like device that delivers the shot. Patients have urged Lilly to ditch the injector for vials, which it uses in other countries but not in the US — even though they are approved by the FDA.

Read more: Why Weight-Loss Drugs Are Billion-Dollar Blockbusters: QuickTake

Meanwhile, patients are finding the drug by any means necessary. 

“I saw a patient yesterday who is having so much trouble finding her Zepbound that she calls CVS pharmacies all over the country and pays someone through Taskrabbit to pick up the med for her and FedEx,” said Katherine Saunders, an obesity medicine specialist at Weill Cornell and the co-founder of Intellihealth.

The patient lives in the northeast, Saunders said. She most recently got the drug from a CVS in New Mexico.

--With assistance from Bill Haubert.

(Updates throughout with new information)

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