Sellers of compounded peptides often promise testing. The wording is familiar. Every compound comes with third-party certificates of analysis. Or: high potency, third-party lab tested, guaranteed.
Few of those pages show a certificate. This page sets out what one should contain. It also sets out what the phrase “third-party lab tested” cannot prove on its own.
What a certificate of analysis is
A certificate of analysis is a lab report for one lot of material. It lists each test run. It gives the acceptance limit and the result.
Federal compounding law uses the term in one place. It applies to the raw ingredient.
Section 503A covers pharmacies. Their bulk drug substances must be “accompanied by valid certificates of analysis” [1]. Section 503B, for outsourcing facilities, uses nearly the same words [2].
FDA reads the 503B wording as one valid certificate for each lot of bulk substance [3]. It recommends the certificate follow an international model for drug specifications.
Federal manufacturing rules allow a supplier’s report in place of full testing of an ingredient [4]. The buyer must still run its own identity test.
That certificate describes the powder the pharmacy bought. It does not describe the vial you received. Dissolving, mixing, filling and storage all happen after it was issued.
What each line on a finished-vial report means
Federal manufacturing rules require a lab check of each batch before release [4]. That check must cover the identity and strength of each active ingredient.
FDA’s draft guidance for outsourcing facilities lists the minimum a finished product should meet [3]. It is still a draft, dated January 2020.
- Identity. Is the molecule the one on the label? The test should name the exact form.
- Strength, or assay. How much drug is in the vial, against how much the label states.
- Purity. How much of the peptide present is the intended molecule, and how much is related impurity.
- Sterility. For injectables. FDA points compounders to USP chapter <71>, Sterility Tests [3].
- Bacterial endotoxins. A limit for injectables. USP’s <797> chapter refers to chapter <85> for the calculation [7].
- Preservative effectiveness. For a multiple-dose vial.
Endotoxins come from bacterial cell walls [3]. They can be present when no living bacteria are, as the study below found. USP says enough in the bloodstream can cause fever and septic shock [7].
Strength and purity are separate lines for a reason. One study shows why.
Researchers test-bought semaglutide vials from illegal online pharmacies selling without a prescription. Three vials arrived. [10]
The labels claimed 99% purity. Measured purity was 7.7% to 14.37% [10].
Yet semaglutide content exceeded the labeled amount by 28.56% to 38.69% [10]. A vial can hold too much drug and still be mostly something else.
No viable microorganisms were found. Endotoxin was detected in every sample, at 2.1645 to 8.9511 EU/mg [10].
That was three vials from unlicensed sellers. It says nothing about any US pharmacy. It shows how far a printed purity figure can sit from a measured one.
Who has to test the finished vial
The answer depends on which kind of compounder made it. The legal routes are covered in are peptides legal. This section is about testing only.
503B outsourcing facilities must follow current good manufacturing practice, or CGMP [5]. FDA inspects them on a risk-based schedule [2].
503A pharmacies are exempt from CGMP by statute [1] [5]. State boards of pharmacy oversee them day to day [5].
A 503A pharmacy follows USP chapter <797> for sterile work. It became official on November 1, 2023 [6].
Under <797>, the lowest category of sterile preparation needs no sterility test at all [7]. Higher categories need one when they carry longer use-by dates.
Even then, a pharmacy may dispense before the result comes back [7]. It needs procedures to tell the prescriber and recall the batch if the test fails.
Registration is not inspection either. FDA’s outsourcing facility list, updated September 24, 2026, had 97 facilities [8].
Forty of them were marked “Not yet inspected” [8]. The table also shows whether an inspection ended with an FDA Form 483.
What “third-party lab tested” leaves out
The phrase answers none of the questions above. It does not say which lot, which test, which lab or when.
It also cannot say what happened after the ingredient was tested. One 2026 analysis shows the gap.
Scientists employed by the maker of brand tirzepatide tested compounded tirzepatide mixed with vitamin B12. They found a widespread, previously unknown impurity [11].
It formed from a reaction between tirzepatide and certain B12 analogs. Its clinical effects are unknown [11].
A certificate for the raw tirzepatide could not show that. Only a test of the finished mixture could.
Form matters too. FDA says semaglutide sodium and semaglutide acetate are different active ingredients from the approved drug [9].
The agency knows of no lawful basis for compounding with them [9]. A certificate reading only “semaglutide” leaves that question open.
So does the pharmacy name. FDA reports compounded semaglutide and tirzepatide labeled with pharmacies that do not exist [9].
Other labels named a real, licensed pharmacy that did not make the product [9].
Then there is “research use only.” FDA has warned companies selling GLP-1 drugs labeled “for research purposes” or “not for human consumption” [9].
FDA says those products are of unknown quality [9]. Pharmacy researchers describe the same channel as a way of bypassing prescribers and pharmacists [12].
A certificate from that channel describes a product not made for people. It does not change what the product is.
What to ask for, in order
Each step takes one message to the seller or pharmacy. Keep the vial and its label.
- Ask for the certificate for the lot number printed on your vial.
- Check the lot number, product name and strength match the label exactly.
- Ask whether it covers the finished vial or only the raw ingredient. Both are called COAs.
- Check the test date. A finished-vial test should fall after compounding and before the use-by date.
- Find the lab’s name. Ask whether it is independent of the pharmacy.
- Look for each line: identity, strength, purity, sterility, endotoxin. Each needs a limit and a result.
- Check the form named in the identity line. A salt form is a different ingredient.
- Look up the pharmacy. Outsourcing facilities appear on FDA’s public list [8].
- Report a quality problem to FDA’s MedWatch program [9].
A seller that cannot produce a lot-matched certificate has told you something. It does not prove the vial is bad. It means the testing claim cannot be checked.
For heat damage in transit, see your peptides arrived warm. For the wider risk picture, see are peptides safe.
For the diluent that goes into a vial, see bacteriostatic water for peptides.