Every compounded medication a clinic orders in the United States comes through one of two sections of the Federal Food, Drug, and Cosmetic Act. Section 503A covers pharmacies that compound for an identified patient on a prescription. Section 503B covers outsourcing facilities that register with the FDA and may compound without one. Which section applies decides who may make the product, what it can be made from, how it is tested and labeled, and whether it may sit on a shelf in your clinic.
This guide explains the difference for clinics, med spas and telehealth practices that order compounded medications. It does not rank pharmacies or facilities.
The Short Answer
- 503A is for a named patient. A state-licensed pharmacy compounds a medication on a valid prescription for one identified patient, who usually takes it home.
- 503B is for office stock. An FDA-registered outsourcing facility compounds in batches under current good manufacturing practice (CGMP) and may ship product to a practice with no patient named, for administration in the office.
- Neither makes FDA-approved drugs. The FDA does not review compounded medications from either source for safety, effectiveness or quality before they are dispensed.
503A and 503B Side by Side
| 503A compounding pharmacy | 503B outsourcing facility | |
|---|---|---|
| Who it is | A state-licensed pharmacy | A compounder registered with the FDA as an outsourcing facility |
| Main regulator | State board of pharmacy, with FDA oversight | The FDA, through registration and inspection, plus state licensing |
| Production standard | USP compounding chapters | Current good manufacturing practice (CGMP) |
| Prescription | Required, for an identified patient | Not required; may also fill patient-specific prescriptions |
| What it supplies | A preparation made for one patient | Batches, including stock for in-office administration |
| Bulk ingredients | A component of an FDA-approved drug, a substance with a USP or NF monograph, or a substance on the 503A bulks list | A substance on the 503B bulks list, or one used to compound a drug on the FDA shortage list |
| Reporting to the FDA | No routine federal reporting | Product reports twice a year, and adverse-event reports |
| Where to verify | The board of pharmacy in the pharmacy's home state and in the patient's state | The FDA's public list of registered outsourcing facilities |
Both sections restrict compounding drugs that are essentially copies of commercially available FDA-approved products.
What 503A Means for a Clinic
Section 503A dates from 1997 and covers the traditional practice of pharmacy compounding. A pharmacy that meets its conditions is exempt from three requirements that apply to drug manufacturers: new drug approval, labeling with adequate directions for use, and CGMP.
The conditions that matter to a clinic:
- A prescription for an identified patient. The pharmacy compounds after it receives a valid prescription, or in limited quantities ahead of prescriptions it expects based on its history with a prescriber. It cannot fill an order "for the practice."
- Licensing where the patient is. The pharmacy needs an active license in the state it ships to, which usually means a non-resident license.
- Limits on copies. A 503A pharmacy may not compound, regularly or in inordinate amounts, a drug that is essentially a copy of a commercially available approved product, unless the prescriber determines and documents a change that makes a significant difference for that patient. The GLP-1 sourcing guide shows how the FDA applies this.
- Limits on ingredients. A bulk substance has to fit one of the three categories in the table above, which is why the status of peptides depends on FDA rulemaking.
The 503A ordering guide covers the workflow in detail.
What 503B Means for a Clinic
Congress created section 503B in the Drug Quality and Security Act of 2013, after contaminated injections from a compounding pharmacy caused a nationwide fungal meningitis outbreak in 2012. An outsourcing facility chooses to register with the FDA, and in exchange it accepts conditions closer to those of a manufacturer:
- CGMP and FDA inspection. Facilities are inspected by the FDA on a risk-based schedule, and the FDA publishes the date and outcome of each facility's last inspection.
- Batch production without a prescription. This is what makes office stock possible.
- Reporting. Facilities report the products they compound twice a year and submit adverse-event reports.
- Labeling. Product is labeled as a compounded drug, and stock shipped without a patient prescription is marked for office use only.
- A narrower ingredient list. A facility may compound from a bulk substance only if the substance is on the 503B bulks list or the drug is on the FDA shortage list. As of October 2026 semaglutide and tirzepatide meet neither test; see the 503B bulks list proposal explained.
The 503B office-use guide covers enrollment with a facility and the records a clinic should keep.
Can a 503A Pharmacy Supply Office Stock?
Not under federal law. Section 503A is built on the prescription for an identified patient, and the FDA's guidance on the prescription requirement says a 503A pharmacy may not supply compounded drugs to a practice as office stock without patient-specific prescriptions.
Some state laws address office use by pharmacies, but a state rule does not waive the federal conditions. If your clinic wants compounded product on hand, the lawful source is a 503B outsourcing facility, and your own state's rules on purchasing and administering office stock still apply.
Which One Does Your Clinic Need?
| Situation | Pathway |
|---|---|
| A patient needs a strength, dosage form or combination that is not commercially available, to take home | 503A, on a prescription for that patient |
| A telehealth practice ships medication to patients' homes | 503A, from a pharmacy licensed in each patient's state |
| A practice administers injections on site and wants stock on hand | 503B, after enrolling with the facility and confirming state rules |
| A practice wants compounded semaglutide or tirzepatide as office stock | Not available from 503B facilities under current rules |
| A controlled substance such as testosterone, kept as office stock | 503B, and the clinic needs its own DEA registration |
A practice that administers medication on site and also sends patients home with prescriptions usually needs both.
Quality: Different Standards, Not a Ranking
CGMP is the stricter production standard. A 503B facility validates its processes, tests batches before release and supports its expiration dates with stability data, which is why 503B product often carries longer dating. A 503A pharmacy follows USP standards written for preparations made for individual patients, where beyond-use dates are shorter by default and release testing depends on the kind of preparation and the size of the batch.
That does not make every 503B product better than every 503A preparation. A 503A pharmacy can make a formulation for one patient, which a batch producer does not do. And registration is not approval: a facility can hold a current registration and still have open inspection findings. Evaluate the individual pharmacy or facility:
- For a 503A pharmacy, check its license and any board discipline in its home state and in your patient's state. Ask about accreditation for sterile compounding, what testing it performs, and how it assigns beyond-use dates.
- For a 503B facility, look it up on the FDA's list of registered outsourcing facilities, which shows the date of the last inspection and whether the FDA issued observations or took further action.
Using Both From One Account
ScriptLinkRx supports both pathways from one account and keeps them apart. A patient-specific prescription starts from a patient record and goes to a 503A pharmacy licensed in that patient's state. An office-use order starts from the clinic's enrollment with a 503B facility and ships to the practice. The two have separate catalogs and separate checkouts, so a patient order is never mixed into an office-stock order.
The partner pharmacy list shows each pharmacy on the network and the states it is licensed in.
Related Reading
- How to choose a compounding pharmacy ordering platform
- The FDA's September 2026 warning letter and what it means for clinics
- PCAC's July 2026 peptide votes
Sources
- FDA: FD&C Act Provisions that Apply to Human Drug Compounding (sections 503A and 503B)
- FDA: Prescription Requirement Under Section 503A of the Federal Food, Drug, and Cosmetic Act (guidance)
- FDA: Compounded Drug Products That Are Essentially Copies of a Commercially Available Drug Product Under Section 503A (guidance)
- FDA: Information for Outsourcing Facilities
- FDA: Registered Outsourcing Facilities
- FDA: Bulk Drug Substances Used in Compounding Under Section 503A
- FDA: Bulk Drug Substances Used in Compounding Under Section 503B
- FDA: Compounding and the FDA: Questions and Answers