503A vs. 503B in 2026: The New Rules for Med Spas and Functional Medicine

For a few years, the GLP-1 shortage made "503A vs. 503B" feel like an academic distinction — with semaglutide and tirzepatide both on FDA's drug shortage list, compounding pharmacies operating under either section had a workable path to producing versions of these drugs, and a lot of clinics never had to think hard about which type of source they were actually using. That workaround is gone. FDA has confirmed the shortage is over, and spent the first part of 2026 spelling out, in specific and narrower terms, exactly what a compounder can and can't do now. Getting the 503A/503B distinction right is no longer optional detail — it's the thing that determines whether your sourcing is currently legal.

The Actual Difference, Not the Marketing Version

Both sections of the Food, Drug & Cosmetic Act let a compounder produce a drug without going through full FDA new-drug approval, but they authorize genuinely different things.

• 503A — traditional compounding: a licensed pharmacist or physician compounds a drug for a specific, named patient, based on a valid prescription. It's primarily governed by state pharmacy practice law, not FDA registration, and it cannot be used to build an ongoing office-use inventory — each preparation is tied to an individual patient.
• 503B — outsourcing facilities: FDA-registered facilities that can compound in larger batches without a patient-specific prescription, sell to a clinic for its own office-use stock, and ship across state lines more freely. In exchange, they're subject to FDA registration, inspection, and current Good Manufacturing Practice (cGMP) requirements that a 503A pharmacy generally is not.
• What this actually means for a clinic: if your clinic wants to keep vials on hand and administer from stock the same day, without a prescription written for each specific patient in advance, that supply has to come from a 503B facility. A 503A pharmacy legally can't supply that model — no matter how the vendor markets it.

The GLP-1 Shortage Is Officially Over, and So Is the Workaround

FDA determined the semaglutide shortage resolved in February 2025 and the tirzepatide shortage resolved shortly after, and gave compounders a wind-down period of enforcement discretion while supply chains caught up. That discretion period has since ended for both drugs. As of this writing, neither tirzepatide nor semaglutide appears on FDA's drug shortage list, and neither appears on the separate 503B bulks list either — which means the shortage-based justification that let so many clinics offer a compounded GLP-1 without much scrutiny no longer applies to either compounding pathway.

This matters for functional medicine and med spa clinics specifically, because compounded GLP-1s — often sold as a lower-cost alternative to the branded product, sometimes combined with other ingredients like vitamin B12 — were one of the most common compounding relationships these clinics built during the shortage years. That relationship needs a fresh legal basis now, not a continuation of the old one.

The Actual New Rule: FDA's April 2026 Clarification

In an April 2026 update, FDA spelled out, more precisely than before, what counts as compounding a drug that is "essentially a copy" of a commercially available product — the category 503A compounders are generally barred from producing regularly or in inordinate amounts. FDA will treat a compounded product as essentially a copy if it has the same active ingredient, in the same, similar or easily substitutable strength, given by the same route of administration as a commercially available product — and that test applies whether the compounded product has one active ingredient or combines the same active ingredient with something else, such as semaglutide combined with vitamin B12. A prescriber can document a genuine, patient-specific reason the compounded version is meaningfully different for that individual patient, which is a real exception, not a formality — but it has to actually be documented, per patient.

The specific new piece is a narrow safe harbor: FDA has stated it does not currently intend to take enforcement action against a 503A compounder for producing an essentially-a-copy product if that compounder fills four or fewer prescriptions of that specific product in a calendar month. That is a real, usable allowance for genuinely occasional, individualized compounding — it is not a return to volume compounding of GLP-1 copies, and a clinic or pharmacy treating it as one is reading well past what FDA actually said.

The 503B side has its own, separate constraint that hasn't loosened at all: an outsourcing facility can only use a bulk drug substance if that substance is on the 503B bulks list or the finished drug is currently on FDA's drug shortage list. Semaglutide and tirzepatide currently satisfy neither condition, which means a 503B facility does not have an open lane to batch-compound these drugs simply because it operates under the section that allows batch production.

What This Means for a Clinic That Wants to Stock Its Own Supply

This is where the distinction gets practical fastest for functional medicine and med spa clinics running an in-house injectable or IV program. If the model is same-day treatment from a clinic-held supply — a vial pulled and administered without a prescription written for that specific patient in advance — that supply has to come from a 503B outsourcing facility, full stop. A 503A pharmacy, even a well-run one, is not legally structured to supply that model, because everything it compounds has to be tied to an individual patient's prescription.

And because 503B facilities are themselves constrained by the 503B bulks list and the shortage list, "we source from a 503B facility" is not, by itself, a complete answer for a GLP-1 program specifically — the facility still needs a lawful basis for the particular substance, which for semaglutide and tirzepatide currently means it isn't there. The clean way to build an office-use GLP-1 or peptide program right now is around what a 503B facility can actually supply lawfully today, not around what the shortage years made routine.

What to Actually Confirm With Your Pharmacy

• Which section your pharmacy is operating under: for each specific product, not as a blanket assumption about the vendor — some pharmacies hold both 503A and 503B licenses and use different ones for different products.
• Whether a product is being compounded per-patient or held as office-use stock: these require different legal bases, and a vendor blurring the line is a sourcing risk, not a convenience.
• Volume tracking against the four-or-fewer threshold: if your clinic is doing individualized, documented-difference compounding of an essentially-a-copy product under 503A, someone needs to actually be counting.
• Documentation of a patient-specific significant difference: where that exception is the basis for a prescription — recorded per patient, not asserted generally across your patient population.
• Current bulks-list and shortage-list status: for any 503B-sourced product, since that status can change and a lawful basis today isn't a permanent one.

Where MedGrid Fits

MedGrid sources exclusively from vendors that clear compounding-pharmacy diligence for the specific pathway your program actually needs — 503A for individualized prescriptions, 503B for office-use stock — and your medical director reviews that sourcing against current bulks-list, shortage-list and enforcement-discretion status as part of a real protocol-review cadence, not a one-time check when the relationship started.

Frequently Asked Questions

• Can my clinic still offer compounded semaglutide or tirzepatide?: Only on a narrower basis than during the shortage years — either through documented, patient-specific compounding under 503A within the four-or-fewer-prescriptions-per-month safe harbor, or from a 503B facility sourcing a substance that's actually on the 503B bulks list or shortage list, which semaglutide and tirzepatide currently are not.
• What's the simplest way to tell 503A and 503B apart?: Ask whether the product is compounded against a specific patient's prescription (503A) or held as stock a clinic administers without one (503B, office use). That single question resolves most sourcing confusion.
• Does the four-or-fewer rule mean my clinic can compound GLP-1 copies again like during the shortage?: No. It's a narrow safe harbor for occasional, individually documented compounding under 503A — not a general return to volume compounding, and not a 503B allowance at all.
• If my 503B vendor says they're FDA-registered, does that clear semaglutide or tirzepatide sourcing?: Registration alone doesn't. The specific bulk substance still needs to be on the 503B bulks list or the drug shortage list, and neither GLP-1 currently is.

This article is general educational information about how 503A and 503B compounding pathways currently work, not legal advice for your specific clinic. FDA's enforcement positions and the bulks and shortage lists referenced here change over time — confirm current status with your medical director and licensed counsel before making a sourcing decision.