“Due to the unprecedented demand for these medicines, some patients may experience difficulty when trying to fill their prescription at their pharmacy,” a Lilly spokesperson said.

The US Food and Drug Administration doesn’t currently consider the obesity shot in shortage and Lilly said it “continues to manufacture and ship all doses of Zepbound.”

Rite Aid Corp. and Amazon Pharmacy said that the drug was in short supply, and multiple pharmacists across the US told Bloomberg News that some or all of the doses of the drug were on backorder.

On the website of Amazon Pharmacy, which has a partnership with Lilly, four doses of Zepbound are listed as unavailable. An Amazon spokesperson confirmed there is a “nationwide shortage” of some weight-loss medications, including Zepbound.

A Rite Aid spokesperson told Bloomberg News the demand for the obesity shot has “created some sporadic supply constraints.”

Other large pharmacy chains, including CVS Health Corp., Walgreens Boots Alliance Inc., and Walmart Inc. did not respond to requests for comment on their Zepbound supply.

Pharmacists say they’re having difficulty ordering the drugs from major wholesalers. On Mar. 25, wholesaler McKesson Corp.’s ordering system displayed to one pharmacist that all doses of Zepbound were on a supplier backorder, with the next release of drugs expected in early or mid-April, according to records reviewed by Bloomberg News. Full recovery of supply was “TBD,” the notice said.

Cardinal Health Inc., another distributor, was also reporting a manufacturer backorder for some doses of Zepbound and limiting shipments to pharmacies, said Richard Glotzer, owner and pharmacist at Drug Mart of Millwood in Westchester County. A CVS pharmacy technician in Ohio, who asked not to be identified, provided the same information.

McKesson and Cardinal did not respond to requests for comment.

— With assistance from Jemima Denham