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FDA has documented subpotent tirzepatide in compounded formulations. That finding, from a 2024 agency sampling program, is now driving a broader oversight shift. The same inspectors who flagged tirzepatide quality failures are likely to turn toward semaglutide compounding next. This article maps that pathway.
1. The news: FDA sampling found subpotent tirzepatide
In late 2024, FDA released results from testing compounded tirzepatide samples. Several vials contained less active ingredient than labeled. One batch tested at 68% of declared strength. Another showed 79%. These are not trivial deviations.
The agency did not name the compounding pharmacies. It did publish the failure rates. Subpotency appeared in both 503A and 503B facilities. That matters because 503B outsourcing facilities are supposed to meet higher manufacturing standards.
Why did FDA test tirzepatide first? Demand. Tirzepatide compounding exploded after the drug went into shortage in 2022. Semaglutide compounding grew even faster. But tirzepatide had a higher price per vial, around $300 to $500 for a month supply from compounders. That made it a priority target.
2. Context: compounding oversight has been uneven
FDA regulates compounded drugs under sections 503A and 503B of the FD&C Act. 503A pharmacies compound for individual patients with prescriptions. 503B outsourcing facilities can compound larger batches without patient-specific prescriptions. Both are supposed to meet quality standards. Enforcement has been patchy.
In 2023, FDA issued warning letters to several compounders for sterility failures. In 2024, the agency began sampling finished compounded GLP-1 products. The tirzepatide results were the first public data release from that program.
Semaglutide is next. FDA has already collected semaglutide samples from compounders. Results are pending. The tirzepatide findings will shape how those results are interpreted.
3. What it means: targeted semaglutide inspections are coming
FDA does not inspect every compounding pharmacy. It prioritizes based on risk signals. Subpotent tirzepatide is a strong signal. It tells the agency that some compounders cannot reliably produce GLP-1 agonists. Semaglutide is chemically similar. The same equipment, the same raw material suppliers, the same analytical methods. If a facility failed on tirzepatide, it likely has semaglutide problems too.
Expect three inspection triggers:
- Any compounder that received a Form 483 for tirzepatide quality issues will get a follow-up semaglutide inspection within 12 months.
- Facilities that purchased tirzepatide active pharmaceutical ingredient (API) from the same suppliers flagged in FDA import alerts will be inspected for semaglutide API sourcing.
- 503B outsourcing facilities with tirzepatide assay failures will face semaglutide assay testing as part of routine surveillance.
This is not speculation. FDA's 2025 compounding inspection work plan lists GLP-1 agonists as a priority class. Tirzepatide results simply moved semaglutide up the queue.
4. Who's affected: compounders, prescribers, patients
Compounding pharmacies that produce both tirzepatide and semaglutide face the highest risk. A single failed tirzepatide assay can trigger a semaglutide-focused inspection. That inspection may include review of batch records, API certificates of analysis, and stability data.
Prescribers who write for compounded semaglutide should verify the pharmacy's quality record. Ask for third-party assay results. If the pharmacy cannot provide them, consider an alternative source. This is not medical advice. It is due diligence.
Patients using compounded semaglutide may see supply disruptions. If FDA issues warning letters or recall requests, some pharmacies will stop production. Others may raise prices to cover compliance costs. A 2024 survey of compounding pharmacies found that GLP-1 testing adds $15 to $25 per vial. That cost gets passed on.
Other peptides are not immune. FDA's panel vote on six peptides included BPC-157, MK-677, Semax, and Hexarelin. Those compounds are not GLP-1 agonists. But the panel's reasoning, that compounding quality data is insufficient, applies across the peptide category. A semaglutide inspection wave could spill over into other peptide products.
5. What to watch next: semaglutide assay results and warning letters
FDA will release semaglutide sampling results in the next two quarters. Expect a similar format to the tirzepatide release: aggregate failure rates, not pharmacy names. If semaglutide failure rates match tirzepatide, warning letters will follow.
Watch for three developments:
- FDA import alerts on semaglutide API from specific overseas suppliers.
- Form 483 observations citing inadequate assay methods for semaglutide.
- State pharmacy board actions against compounders with GLP-1 quality failures.
The tirzepatide findings also inform FDA's draft guidance on compounded GLP-1s. That guidance proposes stricter documentation for peptide compounding. Semaglutide inspections will test whether compounders can meet those standards.
One more link matters. FDA's subpotent tirzepatide finding is the anchor for this entire shift. Without that data, semaglutide inspections would be routine. With it, they become targeted.
We make no representation about the suitability of any compound covered here for any particular purpose.