Retatrutide Molecular Formula and CAS Number Explained
A reference guide to the retatrutide molecular formula and CAS number, explaining what each identifier represents and how to check them against a listing.
Reviewed by Priya Nair, MD, physician, metabolic medicine ·
Priya Nair, MD is a physician with subspecialty training in metabolic disorders and obesity medicine, bringing over a decade of clinical practice expertise to educational content on investigational peptide therapeutics.
The retatrutide molecular formula, as reported across chemical registries and supplier documentation, is C223H347N51O68, and the associated CAS Registry Number is 2381089-83-2. These two identifiers serve different purposes: the molecular formula is a literal count of the atoms making up one molecule of the peptide, while the CAS number is an arbitrary registry index that lets a substance be looked up unambiguously regardless of what trade name or synonym a listing uses. Together, they function as a fixed reference pair that a researcher can check a vial label, a certificate of analysis, or a catalog entry against, rather than relying on the compound name alone.
What the CAS Number Actually Identifies
A CAS Registry Number is assigned once, the first time a substance is indexed by the Chemical Abstracts Service, and it carries no chemical information on its own — it is not derived from the formula, the molecular weight, or the structure. Its value is that it is unique and permanent. If two supplier pages use different names or abbreviations for the same peptide, the underlying substance can still be confirmed as identical if both list the same CAS number.
The format is a string of digits split into groups by hyphens, with the last digit functioning as a check digit calculated from the rest of the number. This is why a mistyped CAS number rarely happens to resemble a real one by accident. When comparing a retatrutide listing against a certificate of analysis, matching the CAS number, 2381089-83-2, against what is printed on both documents is a faster and more reliable cross-check than comparing product names, since naming conventions vary by supplier and are not standardized the way registry numbers are.
Reading the Molecular Formula
C223H347N51O68 is a straightforward atom count: 223 carbon atoms, 347 hydrogen atoms, 51 nitrogen atoms, and 68 oxygen atoms, joined into a single peptide-based molecule. Formulas of this size are typical for larger synthetic peptides rather than small-molecule drugs, because the molecule is built from dozens of amino acid residues linked together, with each residue contributing its own share of carbon, hydrogen, nitrogen, and oxygen to the running total. Retatrutide’s classification as a triple receptor agonist, engineered to interact with three separate metabolic receptor pathways, is part of why its backbone and attached modifications produce a formula this large compared with shorter reference peptides.
The molecular formula and the molecular weight should always be internally consistent, since weight is calculated by summing the atomic weights of every atom the formula lists. A listing or certificate that shows a molecular weight inconsistent with its stated formula is a signal worth checking further, rather than something to dismiss as a rounding difference.
How These Figures Typically Appear Together
Certificates of analysis and supplier specification sheets generally group several identifying fields in one place: substance name, CAS number, molecular formula, molecular weight, and purity as measured by high-performance liquid chromatography. Reading these as a set is more reliable than checking any single field in isolation, since a document that gets one figure right but omits or garbles another is harder to trust as a whole.
| Field | Typical Value for Retatrutide |
|---|---|
| CAS number | 2381089-83-2 |
| Molecular formula | C223H347N51O68 |
| Classification | Triple receptor agonist (GIP, GLP-1, glucagon) |
| Common listing units | mg per vial |
This table reflects the identifiers as they are commonly reported on vendor documentation and chemical reference listings; a specific production batch’s certificate of analysis remains the authoritative document for that particular vial.
Why Formatting Varies Between Sources
The same underlying identifiers sometimes look different across documents without actually referring to a different substance. A molecular formula is occasionally written with element order changed, or with a subscript of 1 dropped by convention where it would otherwise apply, though retatrutide’s formula does not include a single-atom element in this case. CAS numbers are sometimes printed without hyphens as one continuous digit string rather than in the standard grouped format. Neither variation changes the underlying identity of what is being described, but it does mean a researcher comparing two documents should normalize formatting before treating a mismatch as meaningful, and should treat an actual digit or atom-count discrepancy, as opposed to a formatting difference, as the more serious flag.
Readers comparing multiple compounds side by side, rather than checking one listing at a time, often find it faster to start from a catalog view where identifiers are laid out consistently across entries, such as the COA-verified source maintained by HEEZ Research, before narrowing down to a single vial’s specific documentation.
Common Sources of Confusion
Trade names, internal development codes, and marketing shorthand sometimes appear on a listing instead of, or alongside, the compound’s generic name, which is one more reason the CAS number functions as a stable anchor. A listing using an unfamiliar synonym but citing CAS number 2381089-83-2 is still describing the same registered substance, provided the number matches exactly, digit for digit.
Confusion also arises when a listing states only a molecular weight without the accompanying formula, or states a formula without a weight. Because the two are calculated from each other, a complete listing should generally include both, along with the CAS number, rather than presenting a single figure as if it stood on its own. A researcher who only has a molecular weight to work from has less to verify against than one who can check the full formula and CAS number together.
Checking a Listing Against These Identifiers
The practical use of the retatrutide molecular formula and CAS number is as a verification pair, not as trivia. Before treating a vial or listing as confirmed, it is reasonable to check that the CAS number matches 2381089-83-2 exactly, that the molecular formula matches C223H347N51O68 exactly, and that the stated molecular weight is consistent with that formula. A listing that gets all three right is not automatically confirmed as accurate in every other respect, but a listing that gets any of the three wrong is a clear reason to look more closely before treating the rest of its documentation as reliable.
Summary
The retatrutide molecular formula, C223H347N51O68, and its CAS Registry Number, 2381089-83-2, are the two most reliable fixed identifiers for confirming that a listing, vial label, or certificate of analysis refers to the correct substance. Checking both together, and confirming that any stated molecular weight is consistent with the formula, is a more dependable approach than relying on a product name or marketing description alone when comparing documentation across different sources.
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.