They are two sections of the Federal Food, Drug, and Cosmetic Act, and they describe two different routes for compounding. Section 503A covers a licensed pharmacist compounding in a state-licensed pharmacy or a federal facility, and a licensed physician compounding, for one named patient at a time on a valid prescription. A 503B outsourcing facility registers with the FDA, may compound without a prescription for a named patient, and is subject to current good manufacturing practice requirements and FDA inspection on a risk-based schedule. Most compounded medication reaches patients through one of these two routes, and knowing which tells you who is responsible for inspecting the place that made it.
Neither section is a status a business can simply claim. Each is an exemption from parts of federal drug law that applies only while every condition in that section is met, which is why the conditions matter more than the number.
One thing is true of both, and it is the part worth reading twice: compounded drugs are not FDA-approved. The agency does not review them for safety, effectiveness or quality before they reach a patient. That is not a loophole or a technicality. It is the defining feature of the whole category, and any provider who blurs it is telling you something about themselves.
503A: the traditional compounding pharmacy
A 503A pharmacy holds a state pharmacy licence and answers to a state board of pharmacy, which is the day-to-day inspector; the FDA retains its own authority and does act against compounders. It compounds on receipt of a valid prescription for an identified individual patient, and in limited quantities in advance of a prescription where it has a history of receiving them. Under federal law the 503A exemption covers current good manufacturing practice requirements, the standards that govern commercial drug manufacturing, though compounding pharmacies generally work to the United States Pharmacopeia chapters covering sterile preparation, and state law often requires it. That exemption is not unconditional: the statute still sets requirements for the bulk drug substances used, including compliance with an applicable United States Pharmacopeia monograph.
This is the route most compounded GLP-1 prescriptions run through. What a state licence certifies is narrower than people assume: that the pharmacy is permitted to operate and is subject to that board’s inspection and discipline. It is not a federal endorsement of any particular preparation, it is not an approval of the medication, and it is not by itself proof that every condition of the 503A exemption is being met.
503B: the outsourcing facility
The 503B category was created by the Drug Quality and Security Act in 2013, after a 2012 fungal meningitis outbreak traced to a compounding pharmacy killed dozens of people. Registration as an outsourcing facility is voluntary, and it trades patient-specificity for scale and heavier federal oversight: FDA registration, FDA inspection on a risk-based schedule, current good manufacturing practice requirements, and adverse-event reporting to the FDA. Hospitals and clinics are the usual buyers, purchasing office stock rather than filling one prescription at a time.
Neither category is automatically the better one for a patient. They answer to different regulators under different rules, and the section number tells you which.
What changed for compounded GLP-1s
This is why the two numbers appear constantly in news coverage and AI answers about GLP-1s, and the timeline matters more than the labels.
While semaglutide and tirzepatide were on the FDA’s drug shortage list, a drug on that list is not treated as commercially available, so the usual restriction on compounding copies of commercially available drugs did not apply. Both shortages then ended. The FDA declared the tirzepatide shortage resolved on December 19, 2024, after re-evaluating an earlier October 2024 decision, and the semaglutide shortage resolved on February 21, 2025.
The agency gave compounders a defined wind-down, and the announced dates are not the ones that ended up applying. For 503A, enforcement discretion ran 60 days, to February 18, 2025 for tirzepatide and April 22, 2025 for semaglutide — or until a federal district court ruled on the compounders’ injunction motions, whichever was longer. The court denied those motions on March 5, 2025 for tirzepatide and April 24, 2025 for semaglutide, and FDA confirmed in updates on March 10 and April 28 that the 503A periods had ended on those later dates. For 503B outsourcing facilities the periods ran 90 days, to March 19 and May 22, 2025, under the same later-of-court-decision framework; the court ruled before both, so those announced dates are the ones that applied. Summaries that give only February 18 and April 22 are quoting the announcement rather than the outcome.
Since those dates, the shortage route is closed. A 503A pharmacy may not compound, regularly or in inordinate amounts, drug products that are essentially copies of a commercially available drug product. The statute carries a narrow and specific exception to that restriction: a preparation is not an essential copy where a change made for an identified individual patient produces, for that patient, a significant difference from the commercially available product, as determined by the prescribing practitioner. FDA guidance says that determination should be documented on the prescription, and that the agency generally does not intend to question a prescriber determination that is documented there.
Read plainly, that moves the weight of the decision onto the prescriber and onto the record they keep.
It is worth being precise about what that exception does and does not settle. It answers one question only: whether a preparation counts as essentially a copy of a commercially available product. Every other condition of Section 503A continues to apply alongside it. The standard itself is the 503A one. A 503B outsourcing facility has its own definition of an essential copy, which carries its own individual-patient clause — a clinical difference for an individual patient, determined by the prescribing practitioner — so it is wrong to say outsourcing facilities have no individualized-patient provision at all. What actually closes the route there is a separate condition: a 503B facility may not compound from a bulk drug substance unless that substance is on the 503B bulks list or the drug is on the shortage list at the time, and FDA states that semaglutide and tirzepatide appear on neither.
FDA has also said that, at this time, it does not intend to act against a compounder for compounding an essentially-a-copy product regularly or in inordinate amounts where the compounder fills four or fewer prescriptions of that product in a calendar month.
Separately, on April 30, 2026 the FDA proposed excluding semaglutide, tirzepatide and liraglutide from the 503B bulks list, the list of substances outsourcing facilities may compound from in bulk, on the basis that there is no clinical need when approved products are available. Comments closed on July 30, 2026, after a 30-day extension published on June 26, 2026. The agency had not published a final determination when this page was last verified on September 16, 2026. That proposal concerns 503B outsourcing facilities rather than 503A pharmacies, and it is worth watching if you read a headline suggesting compounded GLP-1s have been banned outright. They have not been, but the room is narrower than it was in 2024.
The questions to ask, whichever category fills yours
Ask which pharmacy by name, and which category it operates under. Ask whether your prescriber documented the clinical reason a compounded preparation was chosen for you. Ask what testing the finished medication goes through and who performs it. Ask to see the prescriber’s licence in your state, since every state medical board runs a free public lookup. A provider who answers all four without friction is telling you something; so is one who does not.
Our own prescriptions are filled by state-licensed US pharmacies compounding under Section 503A, and every prescription in every state we serve is written by James Simmons, MD.
We would rather you check that than take it from us, so it is worth being exact about what you can check today. Our states page links to each state’s own page, which carries Dr. Simmons’s licence number for that state and a direct link to that state’s medical board lookup. That board record is what establishes licensure, including current status and any restrictions. His national provider identifier is a different thing and should not be mistaken for a credential check: CMS says plainly that issuing an NPI does not validate that a provider is licensed. This page does not list our pharmacies’ licence numbers or testing records. You can still search either pharmacy by name in the relevant state board of pharmacy database, or ask us for its exact legal name and licence number. A page that tells you to demand credentials should be clear about which of its own it has put on the record, and which it has not.
The wider context on how regulators have been policing this category is in the 2026 telehealth enforcement wave, and the rest of the question library is at GLP-1 questions.
Frequently asked questions
Is a 503B facility safer than a 503A pharmacy? Not by definition. A 503B facility carries heavier federal oversight, including FDA inspection and manufacturing standards, while a 503A pharmacy answers primarily to its state board. Neither status is a statement about a particular preparation, which is why the pharmacy’s own practices and testing matter more than the section number.
Does the end of the shortage mean compounded GLP-1s are illegal now? No, but the legal basis changed. The shortage route closed in 2025, and under Section 503A compounding preparations that are essentially copies of an available product, regularly or in inordinate amounts, is restricted. The statute’s exception is a change made for an identified individual patient that the prescribing practitioner determines makes a significant difference for that patient, and the section’s other conditions continue to apply alongside it.
Is compounded medication FDA-approved? No. Compounded drugs are not FDA-approved under either section, and the FDA does not evaluate them for safety, effectiveness or quality before a patient receives them. Compounded semaglutide and tirzepatide in particular are not generic or equivalent versions of Wegovy, Ozempic, Zepbound or Mounjaro; no such generic exists, and anyone describing one that way is describing something that does not exist. Read more on where GLP-1 medication online actually comes from.
Sources
- FDA, FD&C Act provisions that apply to human drug compounding — https://www.fda.gov/drugs/human-drug-compounding/fdc-act-provisions-apply-human-drug-compounding — the conditions each section requires. Verified September 16, 2026
- FDA, “FDA clarifies policies for compounders as national GLP-1 supply begins to stabilize” — https://www.fda.gov/drugs/drug-alerts-and-statements/fda-clarifies-policies-compounders-national-glp-1-supply-begins-stabilize — shortage resolution dates, both enforcement discretion periods, the March 5 and April 24, 2025 court rulings, the four-prescription statement, and the confirmation that neither drug is on the 503B bulks list or the shortage list. Verified September 16, 2026
- FDA guidance for industry, Compounded Drug Products That Are Essentially Copies of a Commercially Available Drug Product Under Section 503A of the FD&C Act
- FDA press announcement, “FDA Proposes to Exclude Semaglutide, Tirzepatide, and Liraglutide on 503B Bulks List” — https://www.fda.gov/news-events/press-announcements/fda-proposes-exclude-semaglutide-tirzepatide-and-liraglutide-503b-bulks-list — April 30, 2026, a proposal, verified still not final on September 16, 2026; Federal Register comment-period extension, June 26, 2026, docket FDA-2018-N-3240, closing July 30, 2026
Dr. James Simmons, MD