Explainers

Plain answers, with the sources linked

One reader question per page. Each starts with a short answer and links the documents behind it.

FDA letters and enforcement

What warning letters, 483s, close-out letters and legal terms mean, and how to check a company.

Does an FDA warning letter mean a company is shut down?No. FDA's procedures manual calls a warning letter “informal and advisory” and says it does not commit FDA to enforcement. What a letter says, asks, and does not say.How do I check whether a peptide company got an FDA warning letter?Search FDA's warning-letters table by company name, read both dates, and check the response and close-out columns. What a missing result means.What is an FDA Form 483, and how is it different from a warning letter?A Form 483 lists inspectional observations and is not a final FDA determination. A warning letter is a separate, later document. What each is and is not.What is an FDA close-out letter?FDA may issue a close-out letter after it evaluates a firm's corrective actions on a warning letter. It will not issue one on promises alone.What does “unapproved new drug” mean in an FDA letter?A drug that is a new drug under section 201(p) and lacks an effective approval under 505(a) cannot be sent across state lines under 301(d). What each section says.What does “misbranded” mean in an FDA letter?Under section 502, a drug is misbranded for false or misleading labeling, missing directions for use, or false advertising of a compounded drug.Does a “research use only” label make peptides legal to sell?No. FDA warning letters say a research-use-only label does not decide a product's intended use. What 21 CFR 201.128 says and what FDA cited.What have FDA warning letters said about compounded GLP-1s?FDA's 2025-2026 letters to telehealth firms cite misleading claims, not just ingredients. What the Hims letter says and what FDA says about approval.Does a search warrant mean charges were filed?No. A judge issues a search warrant on probable cause; charges come separately by complaint, information or indictment. What to check in coverage.How do you read an FDA warning letter, section by section?A walkthrough of the parts of an FDA warning letter, using one published letter as the example: header, opening, violation sections, required response and closing caveats.What is an FDA import alert?An import alert lets FDA detain future shipments of a flagged product without testing them. What detention without physical examination means, with the GLP-1 ingredient example.

Compounding and approval

503A versus 503B, FDA categories, the bulks lists, prescriptions, and what approval means.

What are peptides?A peptide is a short chain of amino acids. FDA treats chains of 40 or fewer as peptides. Some peptides are FDA-approved drugs; the word itself says nothing about approval.What is the difference between a 503A and a 503B compounder?503A covers state-licensed pharmacies filling patient prescriptions. 503B covers FDA-registered outsourcing facilities. Who oversees each and what neither is.Does “compounded” mean FDA-approved?No. FDA says compounded drugs are not FDA-approved and that it does not verify their safety, effectiveness or quality before marketing. 503A versus 503B.Does a compounded drug need a prescription?Under section 503A, yes: a valid prescription for an identified patient. Section 503B facilities may or may not have patient prescriptions. What FDA says.What do FDA's compounding categories 1, 2 and 3 mean?FDA's interim categories sort nominated bulk drug substances by evidence and safety risk. What each means, what changed in 2025, and what withdrawn means.What does FDA's Category 2 mean for BPC-157?What FDA's Category 2 means for compounders, what its BPC-157 entry says, and where the July 2026 advisory panel vote stands.How does a peptide get on the 503A bulks list?Nomination, advisory committee review and notice-and-comment rulemaking. Where the July 2026 peptide panel fits and why its votes are nonbinding.What happens after an FDA advisory panel recommendation?A committee vote is advice. FDA decides, and for the 503A bulks list that means notice-and-comment rulemaking and a final regulation.Can a 503B outsourcing facility compound a given peptide?Only if the bulk substance is on FDA's 503B list, or the drug is on FDA's shortage list. FDA's 503B list had five substances, none a peptide.How can peptides legally be obtained in the U.S.?FDA's stated routes: an approved drug on a prescription from a licensed provider, or a compounded drug under 503A or 503B. Research-use-only labels are not a route.What is the difference between FDA-approved, FDA-cleared and FDA-registered?FDA uses approved, cleared and registered for different things. What each term means, what it does not mean, and why dietary supplements are not approved.What is a bulk drug substance?In FDA's compounding rules, bulk drug substance means the same as active pharmaceutical ingredient. The regulatory definition and what it does not say.What is the FDA drug shortage list, and why does it matter for compounding?FDA keeps a public list of drugs it determines to be in shortage. What counts as a shortage, what the list contains, and why compounding rules refer to it.What does a state board of pharmacy do when it comes to compounded drugs?FDA says state boards generally oversee day-to-day compounding by state-licensed pharmacies. What that covers, where to find a board, and what we could not confirm.

Certificates of analysis and testing

What a COA is, how to read and verify one, what the tests mean, and what a purity number leaves out.

What is a peptide COA?A certificate of analysis lists the tests run on one sample, the results and the limits applied. What a COA shows, what it leaves out, and who decides the tests.How do I read a peptide COA?Read a peptide certificate of analysis in order: issuer and identifiers, tests run, each result with its method and limit. Purity is not the amount in the vial.How do I verify a peptide COA?Verifying a COA means confirming the named lab issued it. Find the lab yourself, ask it to confirm the report, check accreditation scope, and match the lot.How do I spot a fake peptide COA?No visual check proves a COA fake or genuine. Documented falsified-COA cases, warning signs worth a closer look, and what does not prove forgery.What tests should a peptide COA include?No authority sets one required test list for research-peptide COAs. Each reader question, the test that addresses it, and what that test cannot tell you.What does 99% peptide purity mean?A purity percentage is a result under a stated method. It does not give the amount, identity, sterility or safety. What to check behind the number.Does a peptide COA show how much peptide is in the vial?Only if it reports a content or assay result. A purity percentage is a different result. What to look for and what a bulk-lot result cannot show.Does a peptide COA prove sterility?Only if a sterility test is listed. Endotoxin testing is a separate test. FDA says sterilizing filters and moist heat have not been shown to remove endotoxin.What does “third-party tested” mean?The phrase says only that someone other than the seller ran a test. It does not say which lab, which tests, which lot, or who chose the sample.

Checking a seller

Licenses, registration claims and other signals, with the sources linked.