Compounding 101
503A vs. 503B Compounding: What's the Difference?
The difference between 503A and 503B is who they make medications for and who regulates them. A 503A compounding pharmacy prepares medications for a specific patient based on an individual prescription and is overseen primarily by state boards of pharmacy. A 503B outsourcing facility can compound larger batches without a patient-specific prescription, registers with the FDA, and must follow current Good Manufacturing Practice (cGMP). Neither produces FDA-approved drugs — both compound.
Key takeaways
- 503A = patient-specific prescriptions, regulated mainly by state boards of pharmacy.
- 503B = outsourcing facilities, can batch-compound, FDA-registered, must follow cGMP.
- Both compound non-FDA-approved preparations.
- Patients typically receive medications from a 503A pharmacy; clinics may stock office-use product from a 503B.
- Logos RX is a 503A compounding pharmacy.
Side-by-side comparison
Both 503A and 503B are defined in the Federal Food, Drug, and Cosmetic Act. The practical differences come down to prescriptions, oversight, scale, and typical use:
| Attribute | 503A pharmacy | 503B outsourcing facility |
|---|---|---|
| Patient-specific prescription | Required | Not required (may batch) |
| Primary regulator | State board of pharmacy | FDA |
| Manufacturing standard | USP <795>/<797>/<800> | cGMP (plus USP) |
| Typical volume | Per-patient | Larger batches |
| Common buyer | Individual patients | Hospitals, clinics (office use) |
| FDA-approved product | No | No |
Which one do patients use?
Most patients receive their personalized medications from a 503A compounding pharmacy, because compounding for an individual is exactly what 503A covers. 503B outsourcing facilities exist mainly to supply healthcare facilities with compounded preparations for office use (for example, clinic-administered injectables), where a patient-specific prescription isn't written in advance.
Logos RX is a 503A pharmacy: we compound each preparation against an individual prescription, whether it's shipped to the patient or coordinated through their provider.
Does 503A vs. 503B affect quality?
Both categories are held to rigorous standards — they're just structured differently. 503A pharmacies follow USP compounding chapters and state board rules; 503B facilities additionally follow FDA cGMP and are subject to FDA inspection. Quality at any compounder is best judged by its licensure, accreditation, testing practices, and track record, not by category alone.
Frequently asked questions
Is 503B safer than 503A?
Neither category is inherently 'safer.' They serve different purposes — 503A for patient-specific prescriptions, 503B for larger-batch office-use supply — and both are held to strict standards. Evaluate any pharmacy by its licensure, accreditation, and testing.
Can a 503A pharmacy compound without a prescription?
No. A defining feature of 503A compounding is that it's done for an identified patient based on a valid prescription.
Related reading
Work with a 503A compounding pharmacy
Logos RX compounds personalized medications in Tampa and ships nationwide within our licensed states. Providers can prescribe through our portal.
Educational content. Compounded medications are not FDA-approved and require a prescription. Last reviewed June 2026.