Tesamorelin CAS Number and Molecular Formula Explained
A reference breakdown of the tesamorelin CAS number and molecular formula, covering how these identifiers appear on certificates of analysis and listings.
Reviewed by Yuki Tanaka, PhD, molecular biologist ·
Yuki Tanaka, PhD is a molecular biologist with a doctorate from Osaka University and postdoctoral training at Stanford School of Medicine, specializing in growth hormone axis biology, GHRH receptor signaling, and synthetic peptide analog mechanisms.
The tesamorelin CAS number is 218949-48-5, and its molecular formula is C221H366N72O67S1. These two identifiers function as a fixed reference pair: the CAS number is a registry index assigned by the Chemical Abstracts Service, and the molecular formula is a count of the atoms that make up one molecule of the peptide. Together they let a researcher confirm that a vial label, a certificate of analysis, and a supplier listing all describe the same substance, rather than relying on the name alone, which can be spelled or abbreviated inconsistently across sources.
Why the CAS Number Matters as an Identifier
A CAS Registry Number is a unique numeric label assigned to a specific chemical substance the first time it is indexed. It carries no chemical meaning on its own — it is not derived from molecular weight, structure, or formula — but it is unambiguous. Two suppliers using different trade names or synonyms for tesamorelin will still list the same CAS number if the underlying substance is identical.
The format itself is standardized: a string of digits broken into groups by hyphens, with the final digit serving as a check digit calculated from the preceding numbers. This check digit is why a mistyped CAS number rarely resembles a valid one. When cross-referencing a listing or certificate of analysis, matching the tesamorelin CAS number against 218949-48-5 is a faster and more reliable check than comparing product names, since names are chosen by marketing rather than by a registry body.
Reading the Molecular Formula
The molecular formula C221H366N72O67S1 is a straightforward count of atoms: 221 carbon atoms, 366 hydrogen atoms, 72 nitrogen atoms, 67 oxygen atoms, and one sulfur atom, joined into a single peptide chain. Peptide molecular formulas are large compared with small-molecule drugs because a peptide is built from dozens of amino acid residues strung together, and each residue contributes its own carbon, hydrogen, nitrogen, oxygen, and sometimes sulfur atoms to the total.
This formula corresponds to a specific molecular weight, which listings and certificates of analysis typically express in daltons or grams per mole. The molecular weight is calculated directly from the formula by summing the atomic weights of every atom it contains, so a formula and its associated molecular weight should always be internally consistent. If a listing shows a molecular weight that does not match what the stated formula would produce, that is a signal to check the source more carefully rather than assume a rounding difference.
How These Identifiers Appear on Documentation
Certificates of analysis for research peptides generally list several identifying fields together: the substance name, the CAS number, the molecular formula, the molecular weight, and often the purity as measured by high-performance liquid chromatography. Reading these fields as a set, rather than any single one in isolation, is the more reliable way to confirm a document actually corresponds to the vial it accompanies.
| Field | Typical Value for Tesamorelin |
|---|---|
| CAS number | 218949-48-5 |
| Molecular formula | C221H366N72O67S1 |
| Sequence length | 44 amino acid residues |
| Common listing units | mg per vial |
Sequence length is a useful secondary check alongside the CAS number and formula. Tesamorelin is a 44-amino-acid peptide, and this residue count is what produces the relatively high atom totals in its molecular formula compared with shorter peptides. A listing describing a much shorter or longer sequence under the tesamorelin name would be inconsistent with the registered formula.
Common Sources of Confusion
Synonyms and brand-associated names sometimes appear on listings alongside or instead of the generic compound name, which is one more reason the CAS number is useful as a fixed anchor point. A listing that uses an unfamiliar synonym but cites CAS number 218949-48-5 is still describing the same registered substance.
Formatting differences are also common and do not change the underlying identity of the compound. A molecular formula might be written with the sulfur count omitted, since a subscript of 1 is often dropped by convention, so C221H366N72O67S is the same formula as C221H366N72O67S1. Similarly, some documents write the CAS number without hyphens as a continuous digit string. Neither variation changes what the identifier refers to, but a researcher comparing documents from different sources should normalize formatting before treating a mismatch as meaningful.
For researchers who want to independently verify a stated molecular weight against a listed formula, resources such as HEEZ Research maintain compound reference pages that list these identifiers alongside sourcing information, which is a useful cross-check when a certificate of analysis looks unfamiliar or incomplete. Cross-referencing against more than one independent source is a reasonable practice whenever a document’s identifiers cannot be verified through the original testing lab.
Buyers comparing multiple listings for consistency sometimes find it useful to check pricing pages such as peer tesamorelin listing catalogs alongside the technical identifiers, since a listing that is inconsistent on price relative to comparable vial sizes often turns out to be inconsistent on documentation as well.
Summary
The tesamorelin CAS number, 218949-48-5, and molecular formula, C221H366N72O67S1, are the two most reliable identifiers for confirming that a listing, label, or certificate of analysis refers to the correct substance. Reading them together with sequence length and molecular weight, rather than relying on a product name alone, is the more dependable way to verify documentation across different suppliers and formats.
A note on how to read this
This article is written for research and educational reference. The materials described are sold for laboratory research and are not for human consumption. Nothing here is dosing guidance, a prescription, or a clinical recommendation.