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Most telehealth operators can name their pharmacy. Far fewer can say which kind of pharmacy it is.
That gap costs money. The letters 503A and 503B come from sections of the Federal Food, Drug, and Cosmetic Act, and they describe two different kinds of compounder with different rules, different economics and different risks. If your offer depends on a compounded product, the category your partner falls into shapes what you can promise, what you will pay and what could go wrong.
Educational, not legal advice. Confirm everything about your own supply chain with qualified counsel and your clinical leadership.
What are 503A and 503B?
They are two sections of federal law governing two kinds of compounders.
Section 503A: traditional compounding
Under FDA's description, 503A compounders are not a voluntary category. Their drugs must be compounded after receiving a valid patient-specific prescription. They are exempt from FDA pre-market approval, CGMP requirements and the requirement for adequate directions for use on the label.1
Section 503B: outsourcing facilities
Section 503B covers a voluntary category called outsourcing facilities. An outsourcing facility, per FDA, is a facility that compounds sterile drugs, has elected to register with FDA and complies with all section 503B requirements. It is subject to CGMP, FDA inspects it on a risk-based schedule, and it must report adverse events and give FDA information about the products it compounds, including a list of drugs compounded in the previous six months submitted each June and December.2
Unlike 503A, a 503B facility can distribute under a patient-specific prescription or under a provider order not tied to an individual patient, and office use, such as office stock, is permitted.1
| 503A | 503B |
|---|---|
| Traditional compounding for an individual patient | Outsourcing facility registered with FDA |
| Patient-specific prescription required | Patient-specific prescription or non-patient-specific order |
| Exempt from CGMP | Subject to CGMP |
| Not a voluntary category | Voluntary registration |
| Exempt from FDA approval | Exempt from FDA approval, but not from CGMP |
| Works prescription by prescription | Reports adverse events and product lists to FDA |
Does either category mean the drug is FDA-approved?
No. This is the most important sentence in the post for marketers.
Compounded does not mean approved
FDA states plainly that compounded drugs are not FDA-approved and that it does not review their safety, effectiveness or quality before they are marketed.3 It also notes that compounded drugs can meet important medical needs but may pose risks to patients.3
STAT News walked through the same distinction in a video it posted on November 26, 2024, and added the part that matters for timing:
Compounders must cease production of these drugs as soon as they come off the FDA shortage list
That video came out before the FDA's February 2025 announcement, which put dates on it. The principle is the one to design around: the flexibility follows the shortage, not the pharmacy category.
VideoSTAT
How compounding pharmacies can make GLP-1 weight loss drugs
A plain-English explainer on how compounders, telehealth companies and shortage lists fit together.
Registered does not mean approved
Registered does not mean approved. An outsourcing facility chooses to register and is inspected. That is a regulatory status of the facility. It is not an approval of the drug. If your ad or page says anything like "FDA-approved" about a compounded product, or implies that a registered facility makes its product equivalent to an approved one, you have a claims problem.
The pharmacy's category is a fact about the pharmacy. It is not a claim you get to put on the product.
What does the category change for an operator?
Four practical things.
Pricing and supply
A 503B facility can supply orders that are not tied to one patient. A 503A pharmacy works prescription by prescription. That can shape cost structure, speed and how you manage inventory and patient flow. Check with your own partners rather than assuming a rule of thumb.
Quality systems
Because 503B facilities must follow CGMP and are inspected, the quality system is part of the category. 503A compounders are exempt from CGMP under federal law, which is part of why the choice of partner and the questions you ask matter.1
Risk and accountability
When something goes wrong with a patient, a batch or a claim, "who is responsible" depends on the model. Ask counsel how responsibility flows between your clinic, your clinicians and your pharmacy.
The shortage clock
Both categories have been relying, for some GLP-1 products, on shortage-related flexibility. FDA announced on February 21, 2025 that the semaglutide shortage was resolved, with enforcement periods ending April 22, 2025 for 503A and May 22, 2025 for 503B.4 On March 10, 2025 FDA noted those semaglutide periods run until the later of the listed dates or a court decision on the injunction motion, and that for tirzepatide the 503A period ended after a March 5 court denial and the 503B period ended March 19, 2025.4
How should you read what a pharmacy says about itself?
Pharmacy websites and sales decks are full of badges. Know what each one claims and what it does not.
- "FDA registered." For an outsourcing facility, registration is a status. It is not approval of the drugs it makes.
- "CGMP compliant." A 503B facility must meet CGMP, and FDA inspects on a risk-based schedule.2 Ask for documentation, not a logo.
- "Licensed." Licensing is usually a matter of the relevant state authorities. Ask which states, and for what.
- "Certified." A third-party certification (see LegitScript and the Telehealth Ad Approval Bottleneck) is a different thing from FDA approval or oversight.
Ask for the paper behind every badge, and match it to the claims you put in your own marketing.
What should you ask your pharmacy partner?
Put these in writing, with a date.
- Which category are you, 503A or 503B? If 503B, is the facility registered with FDA?
- How do you supply us: patient-specific prescriptions, office orders or both?
- What is your plan for each product after the shortage-related dates?
- What documentation do you require from our prescribers for any patient-specific preparation?
- What quality documentation can you share, and how do you handle recalls and adverse events?
- How will you tell us about changes in advance?
How should this change your marketing?
Write claims to the facts, not the vibes.
Say less, and say it accurately
Do not call compounded products FDA-approved (more on this in what clinics can and cannot claim). Do not borrow the language of approved drugs. Do not imply that a pharmacy category equals clinical equivalence. Describe your clinical process, your clinicians and your patient support. Those are things you control and can prove.
Keep your pages current
If your product is changing because of the dates above, your pages, ads and scripts need to change with it. A page that describes last quarter's offer is a liability.
The point of understanding 503A and 503B is not to become a lawyer. It is to stop treating "the pharmacy" as one thing, so the offer you build rests on the right kind of partner and the claims you make stay inside the lines. For how I think about clinic offers more broadly, see my telehealth page.
Keep building.Ekai
Questions people ask
What is the difference between 503A and 503B?
Section 503A covers traditional compounding for an individual patient on a patient-specific prescription, with exemptions from FDA approval, current good manufacturing practice and adequate-directions labeling. Section 503B covers outsourcing facilities, which voluntarily register with FDA, must follow current good manufacturing practice and are inspected by FDA.
Are compounded drugs FDA-approved?
No. FDA says it does not review the safety, effectiveness or quality of compounded drugs before they are marketed. Registration of an outsourcing facility is not approval of its products.
Can a 503B facility supply office stock?
Per FDA's description, outsourcing facilities can distribute under a patient-specific prescription or a provider order not tied to an individual patient, and office use is permitted for orders such as office stock.
When do the semaglutide grace periods end?
FDA announced on February 21, 2025 that the shortage was resolved, with periods ending April 22, 2025 for 503A and May 22, 2025 for 503B. On March 10, 2025 FDA noted those periods run to the later of the listed dates or a court decision on a pending injunction motion.
Sources
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