503A Pharmacy Testing: Sterility, Potency, and the COA
Compounded medications are not FDA-approved. The FDA does not review them for safety, effectiveness, or quality. Compounded semaglutide and tirzepatide are not the same as brand-name products and may differ in formulation, purity, and potency.
When a prescription for a compounded GLP-1 reaches a 503A pharmacy, several steps happen before a vial ships. Some of those steps are required by federal law or state rules, and some depend on the pharmacy. This article explains what a 503A pharmacy must do, what it does not have to do, the tests a pharmacy may run, and how you can ask about your own lot.
What a 503A pharmacy is
A 503A pharmacy is a traditional, state-licensed compounding pharmacy. Under section 503A of the federal Food, Drug, and Cosmetic Act, it compounds for an identified individual patient based on a valid prescription, and a licensed pharmacist does the compounding.[1][2] State boards of pharmacy have primary responsibility for day-to-day oversight of these pharmacies; the FDA also conducts surveillance and for-cause inspections.[3]
A 503B outsourcing facility is different. It registers with the FDA, is subject to CGMP requirements, is inspected by the FDA on a risk-based schedule, and can make larger batches.[2][3] That distinction is covered in 503A vs 503B Compounding Pharmacy. What follows is about the sterile preparation of an injectable GLP-1 at a 503A pharmacy.
Sterile compounding: the environment comes first
Injectable medications must be sterile. In the US, the standard for compounding sterile preparations is USP General Chapter 797, usually written as USP 797. USP says the chapter covers requirements including the responsibilities of compounding personnel, training, environmental monitoring, storage, and testing of finished preparations.[4] The current revision became official on November 1, 2023.[5]
Federal law ties 503A compounding to USP standards: the ingredients a 503A pharmacy uses must meet an applicable USP or National Formulary monograph, if one exists, and the USP chapter on pharmacy compounding.[1] USP itself has no role in enforcement. USP says compliance is the responsibility of the applicable regulatory jurisdiction, and that regulators such as state boards of pharmacy may set their own official dates.[5] In practice, that makes your state board of pharmacy the place to check a pharmacy’s license and inspection record.
The four tests that matter
There is no single federal testing requirement for every 503A preparation. Drugs compounded by a 503A pharmacy are not subject to CGMP requirements, and the FDA says quality standards differ by setting.[3] Under USP 797, some sterile preparations must be sterility tested, and some must also be tested for bacterial endotoxins, depending on how they are made and how long a beyond-use date the pharmacy assigns.[5] Whether a lot is tested for potency or purity also varies by pharmacy. These are the four tests to ask about.
Sterility
Checks whether the tested units contain viable microorganisms. USP notes that a sterility test does not guarantee an entire batch is sterile, only the units tested.
Bacterial endotoxins
Checks for endotoxins, fragments of bacteria that can cause fever and other reactions when injected. USP 797 requires it for some injectable preparations and recommends it for others.
Potency (assay)
Measures how much active ingredient the preparation contains compared with the label. Ask whether your lot was tested and what range the pharmacy accepts.
Purity and identity
Checks that the preparation is the labeled compound and looks for contaminants or degradation. For semaglutide, also ask which form of the active ingredient the pharmacy uses.
That last question matters for semaglutide. The FDA says some compounders may use salt forms such as semaglutide sodium or semaglutide acetate, which are different active ingredients from the one in FDA-approved semaglutide products, and that it is not aware of any lawful basis for using them in compounding.[6]
The certificate of analysis
A certificate of analysis, or COA, is the lab report for a specific lot. It usually lists the tests run, the results, the lot number, and the test dates. You can ask the pharmacy for the COA for your lot.
When you get it, check three things: that the lot number matches your vial, who ran the test (an independent lab or the pharmacy’s own lab), and what was tested. Because testing practices vary, a COA that covers only one test, or no COA at all, tells you something about how that pharmacy works. If a pharmacy publishes statements about its own testing, treat them as the pharmacy’s own claims and ask for the COA for your lot.
Beyond the batch: accreditation and inspection
Some compounding pharmacies hold voluntary accreditation, such as PCAB accreditation, which is now offered through the Accreditation Commission for Health Care (ACHC).[7] Accreditation does not replace a state license, and a pharmacy without it can still be properly licensed. If a pharmacy says it is accredited, confirm it with ACHC directly.
State boards of pharmacy license and inspect pharmacies in their jurisdictions, and the FDA can inspect 503A pharmacies through surveillance and for-cause inspections.[3] The FDA publishes its warning letters in a searchable database.[8] None of these records makes a compounded product FDA-approved, but each is something you can check.
An honest word on the limits
Compounded medications are not FDA-approved, and the FDA does not review them for safety, effectiveness, or quality before they are marketed.[3] The steps on this page are real controls, but they are not the same as the premarket review and manufacturing controls behind an FDA-approved drug. Testing practices also vary from pharmacy to pharmacy. That is why the specific pharmacy matters, and why it helps to check it yourself with How to Vet a Compounding Pharmacy: A Checklist.
How to verify your own medication
You can check most of this yourself. Look up the pharmacy’s license in your state board of pharmacy’s database; the FDA’s BeSafeRx page links to each state.[9] If a pharmacy says it holds an accreditation, confirm it with the accrediting body. Search the FDA’s warning letter database for the pharmacy’s name.[8] Ask for the certificate of analysis for your lot. For a fuller walkthrough, see How to Choose a Safe Compounding Pharmacy.
The bottom line
Between a prescription and a vial, a 503A pharmacy works under section 503A, its state board’s rules, and USP compounding standards. It does not have to meet CGMP requirements, and testing practices vary, so the questions to ask are which tests were run on your lot, who ran them, and whether you can see the certificate of analysis. None of this makes a compounded product FDA-approved.
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For the contrast, The Grey Market: Why Overseas GLP-1s and Peptides Are a Gamble covers what goes wrong when a seller skips these steps. For a step-by-step checklist, read How to Vet a Compounding Pharmacy: A Checklist, and see Compounding Pharmacy Profiles and Safety Guides for the rest of this section.
Sources
- 21 U.S.C. 353a, “Pharmacy compounding” (section 503A of the Federal Food, Drug, and Cosmetic Act). Legal Information Institute, Cornell Law School. Accessed October 17, 2026. https://www.law.cornell.edu/uscode/text/21/353a
- U.S. Food and Drug Administration. “Human Drug Compounding Laws.” Content current as of December 17, 2024. Accessed October 17, 2026. https://www.fda.gov/drugs/human-drug-compounding/human-drug-compounding-laws
- U.S. Food and Drug Administration. “Compounding and the FDA: Questions and Answers.” Content current as of September 16, 2025. Accessed October 17, 2026. https://www.fda.gov/drugs/human-drug-compounding/compounding-and-fda-questions-and-answers
- United States Pharmacopeia (USP). “USP Compounding Standards” and “General Chapter 797.” Accessed October 17, 2026. https://www.usp.org/compounding/general-chapter-797
- United States Pharmacopeia (USP). “797 FAQs.” Updated December 11, 2023 (questions 7, 8, 12, 157, and 159). Accessed October 17, 2026. https://pages.usp.org/rs/711-SXF-172/images/USP_HQS_797_FAQs_December2023_V6__002.pdf
- U.S. Food and Drug Administration. “FDA’s Concerns with Unapproved GLP-1 Drugs Used for Weight Loss.” Content current as of October 1, 2026. Accessed October 17, 2026. https://www.fda.gov/drugs/drug-alerts-and-statements/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss
- Accreditation Commission for Health Care (ACHC). “PCAB Accreditation for Modern Compounding Pharmacies.” Accessed October 17, 2026. https://achc.org/pcab-compounding-pharmacy/
- U.S. Food and Drug Administration. “Warning Letters.” Accessed October 17, 2026. https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/compliance-actions-and-activities/warning-letters
- U.S. Food and Drug Administration. “BeSafeRx: Locate a State-Licensed Online Pharmacy.” Accessed October 17, 2026. https://www.fda.gov/drugs/besaferx-your-source-online-pharmacy-information/locate-state-licensed-online-pharmacy
Important: This content is for general education and is not medical advice. Talk with a licensed provider about your situation. Transformation Health is an independent publisher. It does not provide medical care, prescribe, compound, or sell medication, and it does not partner with, vet, or recommend any pharmacy. Compounded medications, including compounded semaglutide and tirzepatide, are not FDA-approved, and the FDA does not review them for safety, effectiveness, or quality. They are not the same as brand-name products and may differ in formulation, purity, and potency. Testing practices vary by pharmacy. A licensed provider decides whether a prescription is appropriate. Transformation Health does not accept payment from providers. How we make money.