Retatrutide pens UK: strengths, formats and price per mg

What a retatrutide pen is

In a research catalogue, a retatrutide pen is a sealed, pre-filled container holding a stated amount of retatrutide, sold as a laboratory research material. The pen is the format, retatrutide is the compound, and the label strength, such as 40mg, is the stated amount in the container. Check each of those facts separately, because none of them tells you the others.

Vivora's Retatrutide 40mg pen is one pre-filled research pen, packed in its own sealed, batch-coded window box, under catalogue code VV-RT. It is supplied for laboratory research only. It is not a medicine, it is not for human or animal use, and it comes without preparation, dosing or administration guidance.

Reta, GLP-3 and LY3437943: the names

Retatrutide turns up under several names. "Reta" is common shorthand in listings and conversation. "GLP-3" is an informal nickname that alludes to the compound's three receptor targets; it is not a scientific name. The research literature uses either the name retatrutide or the development code LY3437943, and the two refer to the same compound: a 2023 Phase 2 trial report introduces it as retatrutide (LY3437943) (PubMed 37366315).

Vivora's product page records the research code LY3437943, CAS number 2381089-83-2, the molecular formula C₂₂₁H₃₄₂N₄₆O₆₈ and a molar mass of 4731.3 g/mol. For your own records, use the name retatrutide with the research code beside it. Nicknames are fine in conversation, but they make records harder to search and easier to confuse with other compounds.

Retatrutide is also easy to confuse with tirzepatide, whose name sounds similar and whose research code is LY3298176. They are different compounds with different receptor targets, and Vivora sells them as separate products under separate catalogue codes: VV-RT for retatrutide and VV-TZ for the Tirzepatide 40mg pen.

Receptor targets

Retatrutide was described in a 2022 paper in Cell Metabolism, by researchers at Eli Lilly and Company, as a triple agonist peptide at three receptors: the glucagon receptor (GCGR), the glucose-dependent insulinotropic polypeptide receptor (GIPR) and the glucagon-like peptide-1 receptor (GLP-1R) (Coskun et al., 2022, PubMed 35985340). The same abstract reports that, in vitro, the compound shows balanced activity at the glucagon and GLP-1 receptors and more activity at the GIP receptor.

An agonist is a molecule that binds to a receptor and activates it, and retatrutide is a single peptide with agonist activity at all three of these receptors. That is the source of the "triple agonist" description, and of the informal GLP-3 nickname. Vivora's catalogue describes the product in the same terms: a triple receptor agonist at the GLP-1, GIP and glucagon receptors.

Receptor targets describe a compound's pharmacology in published laboratory and clinical research. They are not a description of what a research pen does, and Vivora makes no claims about effects of any kind.

Development stage

Retatrutide is in clinical development. On 22 October 2026, a search of ClinicalTrials.gov for retatrutide returned 33 registered studies, all but one with Eli Lilly and Company as lead sponsor. Fourteen were Phase 3 studies: 5 completed, 8 active but no longer recruiting and 1 recruiting. The rest were 14 Phase 1 studies, 4 Phase 2 studies and one record with no phase listed.

Registry counts change as studies are added and completed, so treat these figures as a dated snapshot and check the registry for the current position. One of the Phase 3 studies, NCT06662383, compares retatrutide directly with tirzepatide.

A trial registry describes studies run under their own approvals and supply arrangements. It has no connection with a research pen bought from a catalogue, and nothing in a registry entry tells you anything about a particular product, batch or listing.

What a pre-filled pen listing should state

Before comparing prices, check that the listing gives you the facts you need to record:

• The compound name, ideally with its research code.
• The label strength per pen, with units.
• The number of pens per box, and therefore the box total.
• The packaging: a sealed box, a batch code and anything else included.
• The price per box, the delivery charge and where both are shown.
• Fill volume and concentration, if your records need them. If a listing does not state them, ask before ordering rather than estimating.
• Any test documentation the seller publishes, with the laboratory, the date and the sample it relates to.

For Vivora's listing the facts are: retatrutide, research code LY3437943; 40mg per pen; one pen per box; a sealed, batch-coded window box; £160 per box, with the UK delivery charge shown before payment.

What a research pen listing contains explains each field in more detail, and the label-reading guide covers the printed label.

Strengths and formats

Retatrutide is listed in more than one format and at more than one label strength across the research market, which is why a box price on its own tells you very little. A pen and a vial with the same label strength are different products: the pen arrives pre-filled in a device, while a vial is a simpler container, often holding a dry preparation. Check the listing rather than assuming.

Vivora sells a single retatrutide format: the 40mg pre-filled pen, one pen per box. It does not sell retatrutide vials, a second pen strength or a multi-pen box. If you need more than one pen, you order more than one box, and from 5 boxes, mixed across the range, the wholesale tiers apply.

When you compare Vivora's pen with another listing, compare it per mg and note the format difference. A higher price per mg for a pen than for a vial is expected, because the pen price covers the device and the filling step as well as the material.

Price per mg

Price per mg is the box price divided by the total stated milligrams in the box. For Vivora's pen that is £160 ÷ 40mg = £4.00 per mg. Delivery changes the figure slightly: UK delivery is currently £4.95 per order, so a single box with delivery is £164.95, or about £4.12 per mg. Each additional box in the same order lowers the delivery share per mg.

Wholesale prices are per box and exclude delivery, the discount rises gradually between tiers, and the written quote is the reference for any wholesale order. These figures use the stated 40mg label strength. If you compare against a listing that quotes a measured amount instead, put both on the same basis first.

Research use only

Vivora supplies retatrutide pens for laboratory research only. They are not a medicine, they are not supplied on prescription, and they are not for human or animal use. Vivora does not provide preparation, dosing or administration guidance and does not answer questions about personal use. Buyers must be 18 or over and must confirm research use before an order is accepted. Orders that indicate human or animal use are cancelled and refunded.

Why a research pen is not a prescription pen explains why the two categories are not interchangeable. Read the research-use policy, then compare the current range.

Common questions

What is a retatrutide pen?

A sealed, pre-filled research pen holding a stated amount of retatrutide (LY3437943), sold as a laboratory research material. Vivora's is one 40mg pen per box.

Is GLP-3 the scientific name for retatrutide?

No. GLP-3 is an informal nickname. The research literature uses the name retatrutide or the research code LY3437943.

What does Vivora's 40mg pen cost per mg?

£160 for 40mg is £4.00 per mg before delivery, or about £4.12 per mg for one box including £4.95 UK delivery.

Does Vivora sell retatrutide vials?

No. Vivora's range is pre-filled research pens only, and retatrutide is offered as a single 40mg pen per box.