503A vs 503B Compounding Pharmacies: Key Differences for Practices
Short answer: Sections 503A and 503B of the Federal Food, Drug, and Cosmetic Act (FD&C Act) are the two federal frameworks for human drug compounding. Section 503A applies to compounding by a licensed pharmacist in a state-licensed pharmacy or federal facility, or by a licensed physician, that is not registered with FDA as an outsourcing facility. Section 503B applies to compounding within an outsourcing facility, a voluntary category created by the Drug Quality and Security Act (DQSA) of 2013 (FDA; FDA). The main contrasts are patient-specific prescriptions, CGMP requirements, and FDA registration and reporting.
This article is general, informational reading for practices. It isn't legal advice, and it doesn't say that any particular substance can be compounded under either section. Confirm specifics with counsel or your pharmacy.
The two categories at a glance
FDA publishes a side-by-side chart of both sections. The table below summarizes selected rows from it (FDA). FDA states the chart is not an exhaustive list of conditions.
| Topic | Section 503A | Section 503B |
|---|---|---|
| Who compounds | Licensed pharmacist in a state-licensed pharmacy or federal facility, or a licensed physician | A licensed pharmacist's direct supervision in an outsourcing facility (not required to be a licensed pharmacy) |
| Patient-specific prescription | Compounding must be based on a valid prescription for an identified individual patient | An outsourcing facility may or may not obtain prescriptions for identified individual patients |
| CGMP | Exempt from current good manufacturing practice requirements if all 503A conditions are met | Not exempt from CGMP requirements |
| FDA registration | No explicit registration condition in 503A | Must register with FDA as an outsourcing facility and meet reporting requirements |
| Adverse event reporting | No explicit condition in 503A | Outsourcing facilities must submit adverse event reports to FDA |
| Labeling | No explicit condition in 503A | Label must carry certain information, including the statement "This is a compounded drug" |
| Interstate distribution | 503A limits interstate distribution under a memorandum-of-understanding framework | No explicit condition in 503B |
| Resale | No explicit condition in 503A | The drug can't be sold or transferred by an entity other than the outsourcing facility that compounded it |
What stays the same
Both categories are compounding, and FDA states that compounded drugs are not FDA-approved, meaning FDA doesn't review them for safety, effectiveness, or quality before they reach patients (FDA). Both require that a bulk drug substance arrive with a valid certificate of analysis and come from an establishment registered with FDA under section 510 (FDA).
503A in more detail
Under 503A, compounding is built around the patient-specific prescription. A pharmacist or physician compounds for an identified patient, and the compounder is exempt from CGMP, adequate-directions labeling, and new drug approval requirements only if every 503A condition is met (FDA). State boards of pharmacy license these pharmacies and regulate them alongside FDA's role. For more background, see what a 503A pharmacy is.
503B in more detail
Outsourcing facilities are subject to CGMP requirements and are inspected by FDA on a risk-based schedule. FDA says they may distribute compounded drugs either under a patient-specific prescription or in response to an order from a health care provider that isn't for an identified individual patient, for example office stock (FDA).
Registration is annual. FDA's list of registered outsourcing facilities (updated as of November 6, 2026) notes that a facility that doesn't re-register and pay the annual establishment fee is removed from the list on January 1 of the following year (FDA). FDA also cautions that registration "does not mean that the facility is making FDA-approved drugs" and doesn't by itself mean the facility complies with CGMP or other conditions (FDA).
Questions practices ask when comparing pharmacies
These are due-diligence questions, not a ranking of either category:
- Which section does the pharmacy operate under, and where is that documented?
- For a 503B facility, is it currently on FDA's registered outsourcing facilities list?
- What does the pharmacy's inspection history show? FDA's list includes the last inspection date and any action taken.
- Does the pharmacy document the source of its bulk drug substances, including a certificate of analysis and the manufacturer's FDA registration?
- Does your state board of pharmacy have any actions on file? FDA notes its list doesn't include state board actions (FDA).
Our peptide compounding pharmacy guide covers the practical side of working with a pharmacy.
Where Biomed Peptides fits
Biomed Peptides is a provider-only supplier of lyophilized product and doesn't hold or claim a 503A or 503B designation, and nothing here implies that any item in our catalog is approved or can be compounded under either section. Pharmacy sourcing questions belong with your compounding pharmacy, counsel, and state board. Licensed practices can apply for provider access to review catalog documentation, and the compounding catalog lists what's available to approved accounts.
FAQ
What is the difference between 503A and 503B?
Section 503A covers compounding by a licensed pharmacist or physician based on a prescription for an identified patient. Section 503B covers outsourcing facilities, which register with FDA, are subject to CGMP, and may supply drugs with or without patient-specific prescriptions.
Do 503A pharmacies have to follow CGMP?
FDA's chart says drugs compounded in accordance with all conditions of section 503A are exempt from CGMP requirements. Outsourcing facilities under 503B are not exempt from CGMP.
Can a 503B outsourcing facility supply office stock?
FDA states outsourcing facilities may distribute compounded drugs under a patient-specific prescription or in response to an order from a health care provider that isn't for an identified individual patient, such as office stock.
Does FDA registration mean a 503B facility's drugs are FDA-approved?
No. FDA states registration doesn't mean the facility is making FDA-approved drugs, and it doesn't by itself mean the facility complies with CGMP or other requirements.
Does Biomed Peptides hold a 503A or 503B designation?
No. Biomed Peptides is a provider-only supplier. Nothing in this article implies a catalog item is approved or compoundable under either section. Confirm with counsel or your pharmacy.
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
- FDA. Human Drug Compounding Laws. https://www.fda.gov/drugs/human-drug-compounding/compounding-laws-and-policies
- FDA. Registered Outsourcing Facilities (updated as of 11/06/2026). https://www.fda.gov/drugs/human-drug-compounding/registered-outsourcing-facilities
- FDA. Questions and Answers: Outsourcing Facility Registration. https://www.fda.gov/drugs/human-drug-compounding/questions-and-answers-outsourcing-facility-registration
Frequently Asked Questions
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