Why there are two sections
The FDA recounts that in 2012 contaminated drugs from a single Massachusetts compounding pharmacy caused more than 750 infections and more than 60 deaths across 20 states. In response, Congress passed the Drug Quality and Security Act, enacted on 27 November 2013 [1].
That law did two things. It removed advertising provisions from the existing compounding section, 503A, that had been found unconstitutional, which settled doubts about whether 503A was still valid. And it created a new section, 503B, for a voluntary category of compounder called an outsourcing facility [1].
Section 503A: the pharmacy route
Section 503A is the route for physicians and for licensed pharmacists working in state-licensed pharmacies or federal facilities. One of its central conditions, the FDA explains, is that the drug is compounded after receiving a valid prescription for a specific patient [1][2].
When its conditions are met, a 503A drug is exempt from three federal requirements: FDA approval before marketing, current good manufacturing practice (CGMP) and labelling with adequate directions for use [1]. State boards of pharmacy have the main day-to-day oversight of these pharmacies, although the FDA can carry out surveillance and for-cause inspections [2].
A second condition matters most for GLP-1 medicines. A 503A compounder may not make, regularly or in inordinate amounts, products that are essentially copies of a commercially available drug [6]. In its guidance the FDA treats a product as such a copy when it contains the same active ingredient in the same, a similar or an easily substitutable strength and the commercial product can be used by the same route, unless a prescriber documents that a change makes a significant difference for a named patient [6]. For now the agency says it does not intend to act when a pharmacy fills four or fewer prescriptions of such a product in a calendar month [6].
Section 503B: outsourcing facilities
The law defines an outsourcing facility as one site at a single address that compounds sterile drugs, has chosen to register with the FDA and meets every requirement of section 503B [3]. Registration is renewed every year with a fee, in a window from 1 October to 31 December; a facility that misses it is dropped from the FDA’s list on 1 January [10].
Its drugs can be exempt from FDA approval and from the adequate-directions labelling rule, but not from CGMP [3]. Outsourcing facilities are inspected by the FDA on a risk-based schedule, must report adverse events, and must send the FDA a list of what they compounded at registration and every June and December [3]. Unlike 503A pharmacies, they may supply drugs either against a patient prescription or on an order from a provider such as a hospital that is not for a named patient, for example as office stock [1].
The copy rule is stricter here. Section 503B bars outsourcing facilities from making a drug that is essentially a copy of one or more FDA-approved drugs; in the FDA’s words, among other things this means a product identical or nearly identical to an approved drug, unless that drug is on the shortage list [6]. There is no monthly allowance like the one described for 503A pharmacies.
Where the ingredients may come from
Compounders sometimes start from bulk drug substances, the raw active ingredients. Both sections limit which ones may be used, and the FDA urges compounders to know their suppliers [4].
Under 503A, a bulk substance must meet an applicable USP or National Formulary monograph and the USP chapter on pharmacy compounding; where no monograph exists, it must be a component of an FDA-approved drug or appear on the FDA’s 503A bulks list [4]. Under 503B, it must be used to make a drug that is on the FDA’s drug shortages list at the time of compounding, distribution and dispensing, or appear on the 503B bulks list of substances with a clinical need [4].
The ingredient’s exact chemical form counts. The FDA notes that semaglutide sodium and semaglutide acetate, salt forms found in some compounded products, are different active ingredients from the one in the approved medicines, and says it knows of no lawful basis for compounding with them [11]. It also states that federal law does not allow retatrutide or cagrilintide to be used in compounding at all [11].
Side by side
The table sums up the federal differences the FDA describes. States add their own rules on top, which the table does not cover.
| Point | 503A | 503B |
|---|---|---|
| Who compounds | Physician, or licensed pharmacist in a state-licensed pharmacy or federal facility [2] | Registered outsourcing facility, by or under the direct supervision of a licensed pharmacist [2] |
| Prescription | Valid prescription for an individual patient [1] | Patient prescription or a provider order, such as office stock [1] |
| Quality standard | Not subject to CGMP [2] | Must follow CGMP [3] |
| Main oversight | State boards of pharmacy; FDA may inspect for cause [2] | FDA, with risk-based inspections [2] |
| Adverse event reports to FDA | Not required by federal law [11] | Required [3] |
| Product reports to FDA | No | At registration, then every June and December [3] |
| Copies of approved drugs | Not regularly or in inordinate amounts; four or fewer prescriptions a month currently tolerated [6] | Not allowed, unless the approved drug is on the shortage list [6] |
| Bulk ingredients | Monograph, component of an approved drug, or 503A bulks list [4] | Drug on the shortage list, or 503B bulks list [4] |
| FDA approval of the product | No [2] | No [2] |
How a shortage changes the rules
The FDA’s shortage list switches off some of these limits. For 503A pharmacies, a drug on the list is not considered commercially available, so the restriction on copies does not apply; every other 503A condition, including the patient-specific prescription, still does [5]. For outsourcing facilities, the bar on near-identical copies lifts for a listed drug, and a facility may make it from a bulk ingredient [5].
The FDA adds two cautions. Compounders may lack the expertise, equipment or business reason to make a drug even when it is listed, and compounded drugs carry a higher risk than approved ones because they are not reviewed before marketing [5]. When a shortage ends, the FDA’s policy gives an outsourcing facility some flexibility to finish orders it received while the drug was in shortage, but the agency may act if it takes new orders, or keeps filling old ones more than 60 days after the drug left the list [5].
Where GLP-1 medicines stand in October 2026
The shortages that allowed widespread compounding of semaglutide and tirzepatide ended in 2024 and 2025, and the transition periods for both kinds of compounder have run out [6]. The full sequence of FDA decisions is in our article on compounded GLP-1s; the table below shows only what it means for each section today.
The 503B proposal remained open when this article was checked. A search of the Federal Register on 20 October 2026 found the May 2026 notice and the June 2026 extension of its comment period, but no final determination [8].
| Item | Semaglutide | Tirzepatide | Liraglutide |
|---|---|---|---|
| FDA Drug Shortages Database | Injection not among current shortages [9] | Injection not among current shortages [9] | Injection listed as currently in shortage [9] |
| Shortage declared resolved | 21 February 2025 [6] | 19 December 2024 [6] | Not resolved [9] |
| End of 503B transition period | 22 May 2025 [6] | 19 March 2025 [6] | Not applicable |
| 503B bulks list | Not on it; FDA proposed on 30 April 2026 not to add it [7] | Not on it; same proposal [7] | Not on it; same proposal [7] |
| Comment period on the proposal | Closed 30 July 2026 [8] | Closed 30 July 2026 [8] | Closed 30 July 2026 [8] |
What both have in common
- Neither produces an FDA-approved drug. The FDA does not check their safety, effectiveness or quality before sale, and a compounded drug is not a generic [2].
- Federal rules against insanitary conditions apply in every setting, whether a pharmacy, an outsourcing facility or a physician’s office [2].
- Biological products cannot be compounded under either section [2].
- Promotion by compounders, including through telehealth companies, must be truthful, not misleading and accurate under federal law [2].
- The FDA says compounded drugs should be used only when a patient’s needs cannot be met by an approved drug [2].
Looking a compounder up
The FDA publishes a weekly-updated table of registered outsourcing facilities; the version checked for this article was updated as of 30 September 2026 [10]. For each facility it shows registration dates, the last inspection, whether a Form FDA 483 was issued, whether a recall took place and any resulting action, such as a warning letter [10].
Read the table with its notes. A Form 483 lists investigators’ observations and is not a final finding of a violation; “open” means the FDA has not yet decided whether to act; and newly registered facilities may appear as not yet inspected [10]. The table does not include actions by state boards of pharmacy, which the FDA suggests checking with the board in the facility’s state [10].
For an ordinary pharmacy, the place to check is the state board of pharmacy. The FDA’s BeSafeRx pages link to each state’s licence database and say not to use an online pharmacy that is not listed there [12]. The FDA also warns that people who buy compounded drugs online or through telehealth platforms may not know which compounder made the product [2].
Questions worth asking about a compounded product
None of these answers makes a compounded product approved, but each one is something the FDA’s pages point to:
- Which pharmacy or facility made it, and is it a 503A pharmacy or a registered 503B outsourcing facility [2][10]?
- Is that pharmacy licensed in your state, according to the board of pharmacy database [12]?
- Is the active ingredient the base form, or a salt form such as semaglutide sodium or acetate [11]?
- What are the concentration and the dose in milligrams as well as in units, and how should the dose be measured [11]?
- Who answers questions about the label and instructions: the FDA points patients to the compounder or the telehealth platform [11].
PepLabo is not affiliated with or endorsed by any compounder, pharmacy, outsourcing facility or telehealth company, and does not sell, recommend or link to any compounded or approved medicine.
