Compounded GLP-1s: What You Need to Understand Before You Buy

Compounded semaglutide and compounded tirzepatide are not FDA-approved medications. That single fact is the one most obscured by the marketing around them, and it is the one that changes what you are agreeing to when you buy.

This subject generates more confusion than any other part of the weight-management market, largely because the language used to sell compounded products borrows heavily from the language used to describe approved ones. If you are new to this class of drug, our complete guide to GLP-1 medications covers the fundamentals.

What compounding actually is

Compounding is the practice of a licensed pharmacist or physician combining, mixing or altering ingredients to create a medication tailored to an individual patient. It has a long and legitimate history: a child who cannot swallow tablets needs a liquid formulation; a patient allergic to a dye needs the product made without it.

What compounding is not is a parallel approval system. Compounded drugs do not go through FDA review. Nobody at the agency has evaluated whether a particular compounded preparation is safe, whether it works, whether the amount of drug in the vial matches the label, or whether the facility that made it manufactures consistently. That is not an accusation against any particular pharmacy. It is a description of the regulatory framework: compounded preparations are exempt from those requirements by design, because they were envisaged as a small-scale response to individual clinical need.

503A and 503B are not the same thing

Two sections of the Federal Food, Drug, and Cosmetic Act govern this, and the distinction matters when you are evaluating a supplier.

• 503A pharmacies are traditional compounding pharmacies. They compound for an identified individual patient in response to a prescription. They are licensed and inspected primarily by state boards of pharmacy. They are not required to comply with federal current good manufacturing practice regulations, and their products are exempt from FDA approval and from certain labelling requirements.
• 503B outsourcing facilities register with the FDA, are subject to FDA inspection, and must comply with current good manufacturing practice. They may compound in larger batches without patient-specific prescriptions, typically supplying clinics and hospitals.

A 503B facility operates under meaningfully more federal oversight than a 503A pharmacy. Neither, however, produces an FDA-approved drug. A 503B product is still a compounded product.

Why compounded GLP-1s appeared, and what changed

Ordinarily, a pharmacy may not compound a preparation that is "essentially a copy" of a commercially available FDA-approved drug. That restriction exists to stop compounding being used as a route around the approval process. It is the reason you cannot generally have a pharmacy make you a cheaper version of a drug that already exists.

There is an exception. When a drug appears on the FDA's drug shortage list, the essentially-a-copy restriction is lifted for that drug for as long as the shortage lasts, so that patients are not left without treatment. Both semaglutide and tirzepatide spent an extended period on that list as demand outstripped manufacturing capacity. That is the legal basis on which a very large compounded market grew.

The FDA subsequently declared both shortages resolved — tirzepatide first, semaglutide shortly after — and set short transition periods before enforcement resumed, with different dates for 503A pharmacies and 503B outsourcing facilities. When those periods expired, the exception that had permitted routine compounding of copies expired with them.

This does not mean every compounded GLP-1 disappeared, and it does not mean every remaining one is unlawful. There are narrow circumstances in which compounding a preparation may still be defensible — a documented clinical need for a formulation that the approved product cannot meet, for instance. It does mean that a business selling compounded semaglutide at scale, to anyone who fills in a form, on the basis of price, is on considerably weaker ground than it was in 2024.

The salt-form problem

The FDA has issued specific warnings about products containing semaglutide sodium and semaglutide acetate. These are salt forms of the molecule, and they are not the same active ingredient as the semaglutide base used in the approved products. They have not been shown to be safe or effective, and they are not permitted as bulk drug substances for compounding.

Salt forms have appeared in compounded preparations, in part because they have been available from suppliers — including overseas suppliers — selling material not intended for use in humans at all. If a pharmacy cannot tell you exactly which form of the active ingredient it uses, where the material came from, and whether that supplier is FDA-registered, that is a complete answer to whether you should buy from it.

Dosing errors

The approved products come in pre-filled, single-patient injection devices that deliver a fixed dose. Most compounded preparations do not. They arrive as a vial of liquid, with syringes, and instructions to draw up a volume yourself.

That is a meaningful change in what is being asked of the patient, and the FDA has received adverse event reports reflecting it. The recurring pattern involves confusion between units of a syringe and millilitres of liquid, resulting in people injecting several times the intended dose. Some of those errors have led to severe nausea and vomiting, dehydration and emergency care. Concentrations also vary between pharmacies, so instructions that were correct for a previous vial may be wrong for the next one.

None of this makes self-measurement impossible — people manage insulin this way every day. It does mean a provider who ships you a vial without a conversation about measuring a dose has skipped an important step. If you are unsure how much to draw up, do not guess. Ask before you inject.

Why the price difference exists

Compounded preparations are usually cheaper, and it is worth being clear about where that saving comes from. It is not efficiency. It comes from the absence of the costs associated with bringing an approved drug to market and keeping it there: the clinical trial programme, the manufacturing validation, the post-marketing surveillance, the regulatory compliance. Those costs are real work that produces real information about a product. When you buy a compounded version, you are not buying the same product more cheaply. You are buying a similar preparation without the evidence and oversight attached to the original.

For some people, on some occasions, that trade may still be a rational one made with open eyes. It is not a trade anyone should make without knowing they are making it.

What to ask any provider offering a compounded GLP-1

1. Is this product FDA-approved? (The honest answer for a compounded GLP-1 is no.)
2. Is it prepared by a 503A pharmacy or a 503B outsourcing facility? What is the name, and in which state is it licensed?
3. What is the exact active ingredient — semaglutide base, or a salt form?
4. Where is the active pharmaceutical ingredient sourced, and is that supplier FDA-registered?
5. Is the product tested by an independent laboratory for potency and sterility, and can I see a certificate of analysis for my batch?
6. What concentration is my vial, and precisely what volume corresponds to my dose?
7. Why is a compounded preparation being recommended for me rather than an approved product?
8. Who do I contact if I have a reaction, and is there a clinician available outside business hours?

A provider practising properly will answer all of these without hesitation. Deflection on the first four is informative. The same evaluative logic applies elsewhere in compounded medicine — our article on the regulatory picture around peptide therapy covers a market with very similar dynamics, and how to spot a prescription mill covers the warning signs of an operation that is not really practising medicine.

The reasonable position

Nobody should be shamed for having looked at compounded options. The approved products have been expensive and, for a long stretch, hard to get. The problem is not that patients considered alternatives. It is a market that has consistently described a non-approved preparation in language borrowed from an approved one.

If the difference between the two options matters to your decision — and it should — the choice between the drugs themselves is a separate question, covered in semaglutide vs tirzepatide. Either way, these are prescription medications that require a clinical evaluation, and a clinician may reasonably conclude that no GLP-1 is appropriate for you. Our weight management service works with FDA-approved products, and you can book a consultation to talk through what applies to your situation.