503A vs 503B Compounding Pharmacies: What a Clinic's Pharmacy Label Tells You

FDA describes compounding as a licensed pharmacist or physician (or, at an outsourcing facility, someone supervised by a licensed pharmacist) combining, mixing or altering ingredients “to create a medication tailored to the needs of an individual patient.” FDA says compounded drugs “can serve an important medical need for certain patients” but “also may pose risks to patients.”

The key fact: compounded drugs are not FDA-approved, which FDA says “means the agency does not review their safety, effectiveness or quality before they are marketed.” They are not generics either. FDA says compounded drugs “are also not the same as generic drugs, which are FDA-approved.”

There is also no such thing as an FDA-approved pharmacy. FDA’s June 2026 page for telehealth companies warns against claiming a drug comes from an “FDA-approved or FDA-licensed pharmacy or outsourcing facility,” adding: “FDA does not approve or license any facility.”

Section 503A of the Federal Food, Drug, and Cosmetic Act (FD&C Act) covers compounding by a licensed pharmacist in a state-licensed pharmacy or federal facility, or by a licensed physician. FDA’s summary of the law highlights these conditions:

• A named patient. Compounding “must be based on the receipt of a valid prescription for an identified individual patient.”
• State oversight. “State boards of pharmacy have primary responsibility for the day-to-day oversight of state-licensed pharmacies.”
• Federal exemptions. Qualifying drugs are exempt from current good manufacturing practice (CGMP) requirements, from labeling “with adequate directions for use” and from new drug approval requirements.
• No routine copies. A 503A compounder may not make essentially copies of a commercially available drug “regularly or in inordinate amounts.” FDA’s April 1, 2026 update describes the exception: a prescriber “determines and documents” a change that makes a significant difference for an identified individual patient.
• Documented ingredients. Bulk drug substances need “a valid certificate of analysis” and must come from an establishment registered with FDA.

Section 503B comes from the Drug Quality and Security Act, passed “in response to the 2012 fungal meningitis outbreak,” according to FDA, and enacted on November 27, 2013. It created outsourcing facilities: compounders of sterile drugs that choose to register with FDA and meet all of section 503B.

• FDA inspections and CGMP. Outsourcing facilities “are inspected by FDA according to a risk-based schedule.” Their drugs can be exempt from FDA approval, “but not from current good manufacturing practice (CGMP) requirements.”
• Prescriptions optional. “An outsourcing facility may or may not obtain prescriptions for identified individual patients.” Compounding is done by or under the direct supervision of a licensed pharmacist, but the facility “is not required to be a licensed pharmacy.”
• Reporting. Facilities must report adverse events to FDA and, each June and December, list the drugs they compounded in the previous six months.
• Labeling. Labels must include statements such as “This is a compounded drug.”
• Bulk limits. A facility may not compound from a bulk drug substance unless the substance is on the “503B bulks list” or the drug is on FDA’s drug shortage list at the time of compounding, distribution and dispensing.

Compounded semaglutide and tirzepatide are not FDA-approved. Some compounding conditions depend on whether a drug is on FDA’s drug shortage list. When those shortages ended, FDA gave compounders a limited period in which it did not intend to act on those conditions. Dates come from FDA’s update page and FDA press announcements.

As of September 16, 2026, we found no final decision on the bulks-list proposal on fda.gov or in the Federal Register. FDA’s announcement of the proposal does not mention 503A pharmacies.

Compounded GLP-1s are not FDA-approved, and FDA has published the safety warnings below.

Dosing errors. On July 26, 2024, FDA warned about dosing errors with compounded injectable semaglutide, including products dispensed in multiple-dose vials. Reports involved patients “measuring and self-administering incorrect doses” amid confusion between milliliters, milligrams and “units,” and health care providers miscalculating doses when “converting from milligrams to units or milliliters.” Some patients “sought medical attention or required hospitalization.”

Adverse event reports. As of May 31, 2026, FDA had received 990 adverse event reports associated with compounded semaglutide and more than 730 associated with compounded tirzepatide. FDA notes it is “not always possible to determine if the adverse event directly resulted from use of the drug.” Some reports may involve doses “beyond what is in the FDA-approved drug label.”

Salt forms. FDA says salt forms “should not be used to compound semaglutide” and explains that salt forms, “including semaglutide sodium and semaglutide acetate, are different active ingredients than are used in the approved drugs.”

Counterfeits and shipping. Counterfeit drugs, FDA warns, “could contain the wrong ingredients, contain too little, too much or no active ingredient at all.” FDA also recommends that patients “not use any injectable GLP-1 drug that arrives warm or with insufficient refrigeration.”

Reporting. FDA encourages patients, health care professionals and compounders to report adverse events or quality problems to its MedWatch program, online or on consumer Form FDA 3500B.

1. Get the exact name and address. Ask the clinic for the pharmacy’s legal name, city and state, and compare them with your label. FDA’s telehealth red flags include labels with spelling errors or “incorrect addresses of the pharmacy.”
2. Search your state board of pharmacy. FDA calls this license check “an important step,” links to each state’s license search and says: “If your online pharmacy is not listed, you should not use that pharmacy.” NABP keeps a directory of state boards.
3. For a 503B claim, check FDA’s list. FDA’s registered outsourcing facilities table is updated weekly (the version we read was dated September 8, 2026). It shows registration dates, the last inspection, whether a Form FDA 483 was issued, recalls and any action taken. FDA notes that a Form 483 “does not constitute a final agency determination.”
4. Search FDA’s warning letters. FDA suggests the term “telehealth” in its warning letter database; search the pharmacy’s name too.
5. Check NABP’s Safe.Pharmacy. NABP says a website ending in .pharmacy “has been accredited by NABP.” Its Safe Site Search Tool checks a web address, and NABP labels sites “Not Recommended” when they appear out of compliance with its standards or the law.
6. Look up LegitScript status at the source. LegitScript’s lookup page lets you “enter a website to see if it is LegitScript-certified, legitimate, or rogue.” Use it alongside the state license check, not instead of it.
7. Apply FDA’s BeSafeRx test. A safe online pharmacy, per FDA, always requires a doctor’s prescription, provides a U.S. physical address and phone number, has a licensed pharmacist to answer questions and is licensed with a state board of pharmacy.

• Which pharmacy fills my prescription (legal name, city, state), and is it a 503A pharmacy or a 503B outsourcing facility?
• What is its license number in my state?
• Is my medication FDA-approved or compounded? If compounded, is the active ingredient a salt form?
• Will the label state the dose in the same units my prescriber uses, and who explains how to measure it?
• How is the medication kept cold in transit, and what happens if it arrives warm?
• If the pharmacy can no longer fill my prescription, what happens to my plan and any prepaid months?

Our GLP-1 clinic reviews note which pharmacy each company names, and how we review explains how we use that information. Next: our checklist for online GLP-1 clinics.