Where to buy Oxytocin Peptide: sizes, price per mg and how to verify the lot

What "oxytocin peptide" names, and what it does not

Oxytocin is nine residues, Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly with an amidated C-terminus and a disulfide bridge between the two cysteines that closes six of the nine into a ring. Formula C43H66N12O12S2 for the free peptide, average mass 1,007.2 Da, PubChem CID 439302. It is supplied as the acetate salt, hence "oxytocin acetate", and listings write oxytocin, oxytocin acetate and oxytocin peptide; one molecule. The review cited at the foot of this page describes its receptor system, and this page describes the material as laboratory reagent only.

Approved medicines containing oxytocin have existed for decades, and the United States Pharmacopeia carries a monograph for oxytocin as a drug substance. Neither fact transfers to a research vial: what is sold here is a research chemical, not a drug product, and it is not tested to that monograph unless its certificate says so, which is a claim a buyer should read for rather than assume. Listing it is not an approval, an equivalence or a safety claim.

The disulfide is why identity paperwork matters more than usual for this peptide. The bridge is formed in synthesis; a lot where it did not form is 2 Da heavier with two free thiols, a lot where it formed between molecules is a dimer at twice the mass, and in solution the bridge can open and re-form the wrong way. The glutamine and asparagine at positions 4 and 5 add a second, slower route to change by deamidation. All of it is visible on a certificate that prints its numbers.

The reference point for identity is public. PubChem lists Oxytocin (free base) as CID 439302 with molecular formula C43H66N12O12S2, an average molecular weight of 1007.2 Da and a monoisotopic mass of 1006.436 Da. Those are the numbers a mass spectrometer is checked against, and the number a certificate must print beside the observed mass. Acetate is the counter-ion of the solid; the mass spectrometer sees the oxytocin ion, so the theoretical mass on a certificate is the free peptide.

In plain terms: A hormone nine building blocks long, supplied as the acetate salt. What is sold here is a research chemical and not a drug product. The sulphur bridge makes the molecule sensitive to conditions that break it, so identity paperwork matters more than usual.

Oxytocin Acetate for sale: sizes and price per mg

LabFirst lists Oxytocin Acetate in 3 sizes (2mg, 5mg, 10mg) from $35 to $45, priced per vial with the per-mg figure beside it so sizes can be compared without arithmetic. Per mg, the 5mg vial is the cheapest today at $8 and the 2mg the dearest at $17.50, which is the reverse of the usual shape; the table below is the arithmetic, and the per-mg column, not the vial price, is the one to compare.

The volume tiers are per size, not per basket: ten vials of one size take 10% off that line and twenty take 15%, and mixed sizes do not combine. Shipping is a flat $15 on orders under $200 and free from $200, within the United States only, with same-day dispatch on orders placed before 12 PM Pacific on a business day. The cost per mg tool runs the same comparison across any two listings, ours or anyone else's.

Oxytocin has been synthesised at scale for longer than almost any peptide, and it is inexpensive per milligram; the vial, the fill and the laboratory run are most of the price, which is why LabFirst lists 2, 5 and 10 mg vials and the per-milligram figure falls steeply across them. A laboratory qualifying a lot buys the 2 mg vial once and reads the bridged mass and the deamidation peaks on its certificate before buying larger; one using the material buys the size its work needs and compares per milligram.

The price signal is the state of the bridge. A lot that was stored warm, or in solution too long, carries dimer and reduced forms, and such lots get discounted; the chromatogram says whether a markdown is a bargain or a clearance. "Same as the pharmacy product" at any price is a different error, since a drug product's evidence does not transfer to a research vial. The only discounts on this page are the volume tiers, per size and unchanged month to month, and the lot on the vial is whatever the certificate index says on the day.

The certificate a Oxytocin Acetate lot must carry

Three tests answer three different questions, and a certificate of analysis for Oxytocin Acetate is only complete when it carries all three for the exact lot on the vial. Identity is settled by mass spectrometry, and the number to look for on a Oxytocin Acetate certificate is 1006.436 Da monoisotopic (or 1007.2 Da average, if the laboratory reports the deconvoluted average mass). The observed mass should sit within the instrument's stated tolerance of that figure, and the certificate should print both the theoretical and the observed value, not just a tick.

Purity is a separate question, answered by HPLC: how much of what came off the column was the compound. The figure is only interpretable with its method beside it (column, gradient, detection wavelength) and a date, which is what ICH Q2(R2) means when it asks that an analytical procedure be shown fit for its purpose. A percentage with no method and no date is a number somebody typed, and a certificate that carries every test but for a different lot number than the vial is the most common failure of all and the easiest to catch. Net content is the third test and the one most often missing: the milligrams of Oxytocin Acetate actually in the vial, measured, against the size printed on the label.

Identity is the observed mass against 1,006.436 Da monoisotopic for the bridged peptide (1,007.2 Da average), seen in electrospray as m/z 1,007.4 for the singly charged ion and 504.2 for the doubly charged, printed beside the theoretical value. Three readings tell three stories: 1,006.4 is the bridged molecule; 1,008.4 is the reduced form with both thiols free, a different chemical state; about 2,013 Da is a disulfide-linked dimer. One dalton high with a retention shift is deamidation at the glutamine or asparagine. A certificate rounded to the nearest dalton, or reading "conforms" without a number, has not answered the question that matters most for this peptide.

Purity by HPLC should show the chromatogram with its column, gradient and wavelength; the tyrosine gives a usable 275 nm signal, and the reduced form, the dimer and the deamidated forms each elute at their own time on a proper method, which is why the trace matters more than the percentage here. Net content is the third line: oxytocin acetate is, by name, an acetate salt, and quantitative HPLC against a standard, or amino acid analysis, tells you how many of the labelled milligrams are peptide rather than acetate and water. Because a USP monograph exists, a certificate may state that the lot was tested to it; if it does not say so, it was not.

Where to buy Oxytocin Acetate: five checks before you order from anyone

Every seller of oxytocin peptide says "third-party tested". The phrase costs nothing. These five checks take about four minutes per listing and separate a tested lot from a tested-sounding one.

1. The lot on the vial is the lot on the certificate. Read the printed lot number, then open the certificate and match it. A certificate for "Oxytocin Acetate" with no lot, or a lot that does not match, describes some other vial.
2. The laboratory is named and has its own lookup. The report should come from a laboratory the seller does not own, with a search code you can enter on the laboratory's own site. LabFirst lots are tested by Freedom Diagnostics and looked up by accession number; anything that can only be verified on the seller's own page has not been verified.
3. The theoretical mass is printed, and it is the right one. For Oxytocin Acetate that is 1006.436 Da monoisotopic; a certificate that prints a different figure has either measured a different molecule or copied a template.
4. Purity has a method and a date. An HPLC percentage should name the method and the run date. A figure that reads "99%+" with neither, or one date reused across every product a seller lists, is decoration.
5. Net content is stated in milligrams. The label size is a claim; the certificate's net content is the measurement. If the certificate has no net content line, the purity figure describes the powder, not the vial, and the price per mg you calculated is fiction.

How listings for Oxytocin Acetate specifically mislead:

• "USP grade" with no statement that the lot was tested to the monograph. A monograph exists for oxytocin; a certificate that does not say the lot was tested against it is describing a different standard, or none.
• "Same as the pharmacy product". Approved oxytocin medicines are made under approvals to specifications; a research vial has a lot certificate and nothing else, and no equivalence is claimed or possible.
• A certificate reading 1,008 Da and calling it conforming. That is the reduced, unbridged form, 2 Da heavier than the folded molecule; a careful laboratory reports which state it saw.
• "99.9%" with no dimer, reduced-form or deamidation peaks named. A disulfide peptide with a glutamine and an asparagine ages in known ways; a certificate that never sees those peaks may never have looked.

How to verify a LabFirst Oxytocin Acetate lot

The Oxytocin Acetate sizes in stock today carry lot LF-2608-20. Lot LF-2608-20 is at Freedom Diagnostics on accession FD-2026-05716 for identity, purity and net content. Until the report is attached the product page says "pending verification" against that lot and makes no purity claim; the price stands and the report goes live the day it arrives, on the page, at /coa/, and inside the receipt and packing slip for every order of that lot.

Verification runs through the laboratory, not through us. Open the certificate index, find the lot, and use the accession number on the Freedom Diagnostics lookup page; the report you see there is the laboratory's copy, not ours. Each lot also carries a Finnrick verify link, and every receipt and packing slip states that a customer may submit a sealed vial to Finnrick's free testing programme with the order as proof of purchase, so the brand's public record is built from vials we did not choose.

The product page reads the live stock feed on load (stock, lot and certificate state for every size), so what you see when you order is what ships. The lot is printed on the label and encoded in the QR patch on its right-hand side; scanning it opens that lot's record.

Storage and shipping for Oxytocin Acetate

The disulfide sets the storage terms. Lyophilised and sealed at 2 to 8 C out of light, oxytocin acetate keeps its bridge for the shelf period on the certificate; in solution the bridge can open and re-form between molecules, the rate rising with temperature, pH and time, and the glutamine and asparagine deamidate on a slower clock. So a prepared solution is dated, kept cold, kept out of light for the tyrosine's sake, and used inside the laboratory's own stability record rather than any figure on a label. The dry cake's other enemy is water drawn from humid air once the vial is opened; open a vial once, for its purpose, and never re-seal one for storage.

Orders ship within the United States, flat $15 under $200 and free above it, same day when placed before 12 PM Pacific on a business day, and the shipping page states the cutoff, the carriers and what is and is not promised.

The record a laboratory keeps on arrival is what makes the certificate usable later, and it is short:

• the lot number as printed on the vial, and the certificate's accession or search code beside it;
• the date received and the condition of the seal;
• the storage location and temperature it went into;
• the number of vials, and later the date each one was opened and by whom.

A Oxytocin Acetate vial with that record behind it can be traced from the bench to the laboratory report in one step; without it, the certificate is a document about a vial that can no longer be identified.

Regulatory status, and what this page is not

Approved medicines containing oxytocin have been on the market for decades, and the United States Pharmacopeia carries a monograph for oxytocin as a drug substance. Those facts concern drug products and pharmaceutical manufacturers; what is sold here is a research chemical offered as laboratory material only, not made under any approval, not tested to the monograph unless its certificate states so, and not claimed to be equivalent to, as pure as, or a substitute for any medicine. Oxytocin was not among the peptides the FDA moved to Category 2 of its interim 503A bulk substances list in September 2023, and its compounding position, whatever it is, concerns pharmacies rather than laboratory vials.

FOR LABORATORY AND IN-VITRO RESEARCH USE ONLY. NOT FOR HUMAN OR ANIMAL CONSUMPTION. LabFirst sells Oxytocin Acetate to laboratories and researchers as material for in-vitro work, gives no guidance on use, and ships only against that understanding. Nothing on this page or on the product page describes preparing or administering anything.

What is Oxytocin Acetate studied for?

Published research on Oxytocin Acetate investigates the areas below — which is a different question from what Oxytocin Acetate will do for anyone, a claim about a living system that nothing on this site is sold for.

What it is. A hormone nine building blocks long, supplied as the acetate salt.

What the research looks at. A very large body of basic and clinical research on oxytocin exists. Approved medicines containing oxytocin exist for specific uses.

How it is thought to work. It works on the oxytocin receptor. The peptide has a sulphur-to-sulphur bridge holding its shape, and that bridge is the part most easily damaged in handling.

What is not established. What is sold here is a research chemical and not a drug product. The sulphur bridge makes the molecule sensitive to conditions that break it, so identity paperwork matters more than usual.

The full record, including the certificate for the lot in stock, is on the Oxytocin Acetate product page.

Common questions

Sources

• PubChem, Oxytocin (free base), CID 439302. Public record for the molecular formula (C43H66N12O12S2), average molecular weight (1007.2 Da) and monoisotopic mass (1006.436 Da) quoted here as the identity reference.
• Gimpl and Fahrenholz, The oxytocin receptor system: structure, function, and regulation, Physiological Reviews 2001. Primary description of the compound in the literature; supports the class and naming stated here, not any use.
• ICH Q2(R2), Validation of Analytical Procedures (2023) 2023-11. Why a purity figure is only interpretable with its method, and what "fit for purpose" means for the HPLC and mass spectrometry results a certificate reports.
• Freedom Diagnostics, certificate lookup by accession number. The laboratory-side lookup a LabFirst lot is verified on; the report there is the laboratory copy, not ours.
• Finnrick, verify a vendor or lot. Independent verification page linked from every LabFirst lot; customers may submit sealed vials with their order as proof of purchase.