Hundreds of people taking compounded GLP-1 drugs — unapproved versions of brand-name weight loss medications — have reported “adverse events,” with some health issues requiring hospitalization, according to the U.S. Food and Drug Administration (FDA).
As of July 31, 2025, the agency has received a total of 605 reports of adverse events with compounded semaglutide, the active ingredient in Wegovy and Ozempic, and a total of 545 adverse event reports for tirzepatide, the active ingredient in Mounjaro and Zepbound, the FDA said in a statement. The true number of safety issues with compounded GLP-1 drugs is likely higher because many pharmacies that make these products aren’t required to report adverse events to regulators, the FDA said.
Dosing Errors May Be More Common With Compounded GLP-1s
Multiple adverse event reports were related to dosing mistakes with compounded semaglutide injections, which resulted from patients self-administering incorrect doses or healthcare providers miscalculating doses, the FDA said.
Melanie Jay, MD, a professor at New York University and the director of the NYU Langone Comprehensive Program on Obesity Research, points out that most brand-name drugs come in prefilled pens that make it relatively simple to “dial up” the right dose by twisting a knob. People using compounded GLP-1s, however, typically draw the medication from a vial with a syringe.
“When patients have to fill their own syringes, there are more opportunities for dosing errors,” Dr. Jay says.
Some adverse event reports were also related to patients being prescribed doses of compounded semaglutide or tirzepatide that were higher than those for the FDA-approved versions of these drugs, the FDA said.
In some instances, the side effects were serious enough for patients to require medical treatment for symptoms such as nausea, vomiting, diarrhea, abdominal pain, and constipation, the FDA said. Other patients experienced side effects such as redness, swelling, or pain at the injection site.
How Common Are Adverse Events From Compounded GLP-1s?
An FDA spokesperson contacted by Everyday Health didn’t provide additional information to quantify the risk of compounded GLP-1 drugs, such as the total number of people taking compounded GLP-1 medicines or the proportion of these patients who experienced adverse events.
“It’s really hard to get a handle on the actual number of prescriptions and adverse events, including serious adverse events, among people who use compounded semaglutide and tirzepatide,” says Jody Dushay, MD, an endocrinologist and an assistant professor at Harvard Medical School and Beth Israel Deaconess Medical Center in Boston.
“If I had to guess, I’d say this is the tip of the iceberg in terms of adverse events, and I think there is an even larger number of people who are not getting any benefit from these medications,” Dr. Dushay says.
One reason adverse events for compounded GLP-1 drugs are probably underreported is that people who prescribe or sell these drugs don’t hear from patients when there are problems, Dushay says. It’s also likely that some places selling compounded GLP-1 drugs don’t report side effects they learn about to the FDA, Dushay adds.
The FDA tally of adverse events associated with compounded GLP-1 drugs doesn’t prove that these treatments directly caused specific side effects, according to the Alliance for Pharmacy Compounding (APC). It’s possible that health issues people experience while taking compounded GLP-1 drugs are attributable to something other than these medicines, APC notes.
Beyond that, it’s possible that people who experienced adverse events while taking compounded GLP-1 drugs had counterfeit or fraudulent products from unlicensed pharmacies or medical spas — and not from legitimate licensed compounding pharmacies, notes the APC.
States provide licensing to compounding pharmacies that can prepare customized medicines using the same active ingredients in FDA-approved drugs for patients who need a dose or form that isn’t commercially available or is in shortage — which was previously the case with Wegovy and Ozempic.
How to Spot a Fraudulent Compounded GLP-1
The FDA encourages the following safety measures:
Carefully check labels of compounded GLP-1 drugs for warning signs of a counterfeit medication, such as spelling errors or incorrect addresses, and ensure your medicine is from a licensed pharmacy and prescribed by a licensed healthcare provider.
If you receive a product with a licensed pharmacy name on the label that you think might be fraudulent, contact the pharmacy to ask if it is their product.
Talk to your doctor if you have questions about your medicines.
EDITORIAL SOURCES
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Emily Kay Votruba has copyedited and fact-checked for national magazines, websites, and books since 1997, including Self, GQ, Gourmet, Golf Magazine,Outside, Cornell University Press, Penguin Random House, and Harper's Magazine. Her projects have included cookbooks (Padma Lakshmi's Tangy Tart Hot & Sweet), self-help and advice titles (Mika Brzezinski's Know Your Value: Women, Money, and Getting What You're Worth), memoirs (Larry King's My Remarkable Journey), and science (Now You See It: How the Brain Science of Attention Will Transform How We Live, Work, and Learn, by Cathy Davidson). She started freelancing for Everyday Health in 2016.
Lisa Rapaport is a journalist with more than 20 years of experience on the health beat as a writer and editor. She holds a master’s degree from the UC Berkeley Graduate School of Journalism and spent a year as a Knight-Wallace journalism fellow at the University of Michigan. Her work has appeared in dozens of local and national media outlets, including Reuters, Bloomberg, WNYC, The Washington Post,Los Angeles Times, Scientific American, San Jose Mercury News, Oakland Tribune, Huffington Post, Yahoo! News, The Sacramento Bee, and The Buffalo News.
