Tesamorelin lab tests

Seven checks before you trust a Tesamorelin certificate

The same seven questions decide whether a certificate of analysis means anything, whichever compound it describes. Six are about the document; the seventh is about what no document can tell you.

1. An independent, batch-matched COA. The certificate must name the batch or lot in your hands, and must come from a laboratory the vendor neither owns nor pays. A specimen certificate from an earlier lot proves nothing about the vial you were sent.
2. HPLC purity, read against a known band. A purity figure is only informative against the distribution for that compound. "Above 98%" is not a claim — the useful question is whether the result sits inside the range the rest of the market reports. How to read HPLC and mass-spec results.
3. Mass-spectrometry identity. HPLC says how much of the sample is one thing; it does not say which thing. Only a mass-spec result establishes identity, and it is the only check that separates compounds a few daltons apart. Contamination is not hypothetical: research-grade custom peptides from two independent commercial suppliers were found to carry contaminating peptides at roughly 1% by weight, enough to produce false-positive results in immunology assays (Clinical and Vaccine Immunology, 2008 — a study of HIV vaccine peptide libraries rather than of any compound on this site).
4. Net content, measured rather than assumed. Purity and quantity are different questions: a vial can be 99.7% pure and still contain two thirds of the labelled mass. Why 10 mg isn't 10 mg.
5. Endotoxin (LAL) on the batch. An absent endotoxin line means the batch was not tested — not that it passed. Endotoxin testing and LAL interpretation.
6. Who ran the test, and what they left off. A laboratory with a record on this compound, named on the certificate, with a verification route back to it. Testing laboratories we track · Red flags in a certificate of analysis.
7. What no test on the vial can establish. A perfect certificate confirms that a vendor sold the correct molecule at the stated quantity. It says nothing about efficacy, dosing, or long-term safety.

Want a vial tested yourself? How to send a peptide for independent HPLC testing.

What tesamorelin testing has to rule out: the missing hexenoyl group

Tesamorelin is a 44-amino-acid analogue of human growth hormone-releasing hormone — the full GHRH(1-44), YADAIFTNSYRKVLGQLSARKLLQDIMSRQQGESNQERGARARL, not a fragment — modified by a trans-3-hexenoyl group on the N-terminal tyrosine and amidated at the C-terminus: CAS 218949-48-5 (PubChem CID 16137828), C₂₂₁H₃₆₆N₇₂O₆₇S, 5,136 Da. Substitution by a neighbour is easy to catch. Tesamorelin sits 1,778 Da above sermorelin (3,357.9) and 1,489 above CJC-1295 with DAC (3,647.2), gaps unmissable on a mass spectrum and invisible on an HPLC purity certificate. A vial sold as tesamorelin that measures around 3,400 Da is sermorelin, and anything reading in the 3,000s is not tesamorelin regardless of the label.

The subtle identity check is the acylation. The hexenoyl group is what protects the molecule from dipeptidyl peptidase-4 (DPP-4) degradation, and it is the only part of this molecule's identity that a careless synthesis can quietly omit while still producing a 44-residue peptide. A mass reading around 5,040 is unmodified GHRH(1-44), not tesamorelin — the hexenoyl group is roughly the whole difference.

• Mass spectrometry at 5,136 Da on a batch-matched certificate, with the mass matching the hexenoyl-modified form rather than unmodified GHRH(1-44) at around 5,040.
• Database caution: PubChem's CJC-1295 record has had both "CJC1295 With DAC" and "CJC1295 Without DAC" listed as synonyms and subsequently removed them, so treat that record as the DAC form only.
• Fill accuracy: one vendor's sample on this platform tested 23.6% above labelled quantity (verified August 2026). A fill process that runs 23.6% over is not being measured and produces shortfalls just as readily; quantitative content testing is the check.
• Endotoxin (LAL) results are absent from most tesamorelin entries on this platform.