By Dr. Donald L. Gates, MD
Compounded semaglutide purity has been measured, published, and peer-reviewed. The findings are worth reading before your next refill — particularly if you are unsure which pharmacy prepared your vial.
One clarification before the data. This research examined semaglutide obtained from unregulated online sellers. It is not a study of every compounding pharmacy in the country. That distinction matters in both directions. It means a licensed, accredited compounder is a meaningfully different thing. It also means a label claiming 99% purity proves nothing on its own.
What the Published Testing Found
A study in JAMA Network Open analyzed semaglutide purchased from online sources without a prescription. Measured purity ranged from 7% to 14%, against labels claiming 99%.
The same research found that the actual semaglutide content exceeded the labeled dose by 28% to 39%. Patients using those products would have received substantially more drug per injection than intended, without knowing it.
A separate 2024 analysis found that roughly 30% of semaglutide obtained from unregulated online sellers met quality standards. That leaves a majority that did not.
Contamination Is a Separate Problem
Purity is about how much of the vial is the drug. Contamination is about what else is in there.
Endotoxin — a bacterial byproduct that can cause fever, inflammation, and in higher doses serious systemic reactions — was detected in every sample tested in one peer-reviewed investigation, at levels ranging from 2.16 to 8.95 EU/mg.
In February 2025, the FBI issued a public alert warning that some products sold as compounded semaglutide contained no semaglutide at all. Others contained material described as animal grade, which is not approved for human use in any context.
Litigation filings from Novo Nordisk indicate that a substantial share of the active pharmaceutical ingredient used in unregulated compounding originates from facilities outside FDA oversight.
Three Tiers, Three Very Different Standards
Compounded semaglutide purity depends almost entirely on which of these produced it.
503B outsourcing facility: FDA-registered, current Good Manufacturing Practices required, subject to FDA inspection, and adverse events are reportable.
503A pharmacy (licensed): Regulated primarily by the state board of pharmacy, with state rather than federal manufacturing standards, limited inspection, and adverse event reporting that varies by state.
Unlicensed online seller: Effectively no oversight, no manufacturing standard, no inspection, and no adverse event reporting.
Two points about this. First, registration is not approval. A 503B outsourcing facility is registered and inspected, and it still does not produce FDA-approved drugs. No compounded preparation is FDA-approved. Second, the third category is where the alarming purity data comes from. If your medication came from a verifiable, licensed pharmacy with your name on the label and a lot number you can trace, you are not in that category.
How to Find Out Which Category You Are In
Look at your vial and box. You are looking for four things:
The exact legal name of the dispensing pharmacy
A lot or batch number and a beyond-use date
The ingredient form and concentration, stated in milligrams per milliliter
Your name, as the prescription patient
If all four are present, verify the pharmacy with the Georgia State Board of Pharmacy or the relevant state board. If the pharmacy claims 503B status, it should appear on the FDA’s published list of registered outsourcing facilities.
If any of those four elements is missing, bring the vial to a physician before your next dose.
Frequently Asked Questions
Does a certificate of analysis prove compounded semaglutide purity?
Only if it can be tied to your specific lot and comes from a credible independent laboratory. A generic document with no lot linkage does not establish anything about the vial in your refrigerator.
Is compounded semaglutide legal?
Compounding is legal within a defined regulatory framework. The FDA’s position is that compounded GLP-1 drugs should be used only when a patient’s medical need cannot be met by an FDA-approved product. With the semaglutide and tirzepatide shortages declared resolved, the basis for producing copies at scale has ended.
What should I do if I bought semaglutide online without a prescription?
Stop and speak with a physician before your next dose. Bring the vial and any packaging. Purity, ingredient form, concentration, and contamination are all unknown in that scenario, and the dose you believe you are taking may not be the dose you are receiving.
This article is educational and is not a substitute for individualized medical advice. Treatment decisions depend on your medical history, current medications, and clinical circumstances. Talk with a physician before starting, changing, or stopping any medication. If symptoms are severe, rapidly worsening, or feel like an emergency, call 911 or seek emergency care.
About the Author: Dr. Donald L. Gates, MD leads Scale Solutions, a medical weight management practice serving Savannah, Pooler, and coastal Georgia. He earned his medical degree at Loma Linda University and practiced emergency medicine before focusing his career on bariatric and metabolic medicine. At Scale Solutions he treats obesity as the chronic medical condition it is, combining GLP-1 therapy with nutrition counseling and long-term follow-up care.
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