Retatrutide 20mg (R&D Only)
£139.99
Each Retatrutide 20mg Research kit includes:
Pre-filled Research pen (20mg Retatrutide)
Research information sheet
Retatrutide 20mg is the volume format of this compound in the United Kingdom, and it is the sensible starting point for most laboratory work. This pen holds 20mg of retatrutide in a pre filled dial dosing device, priced at £139.99, which works out at £7.00 per milligram and sits squarely inside the normal UK band. Supplied for laboratory research use only and not for human or veterinary consumption.
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Table of Contents
Retatrutide 20mg Specification
| Specification | Detail |
|---|---|
| Compound | Retatrutide, also written LY3437943 |
| Total content | 20mg per pen |
| Format | Pre filled dial dosing pen, solution |
| Price | £139.99 |
| Cost per mg | £7.00 |
| Purity | Above 98 percent, batch documented |
| Storage | 2 to 8 degrees refrigerated, never frozen |
| Classification | Research use only, not for human consumption |
Retatrutide 20mg Cost Per Milligram
Cost per milligram is the only figure that compares formats honestly, because headline prices reward the smallest pen. At £139.99 for 20mg this format costs £7.00 per milligram, against roughly £8.00 to £11.00 for a 10mg pen and £5.50 for our 40mg kit. That places retatrutide 20mg in the middle: better value than any smaller pen, slightly behind the largest kit.
It is also the format where the price floor test matters most, because it is the one counterfeiters imitate. Synthesis, purification, sterile fill and refrigerated logistics impose a hard cost floor, so a 20mg pen advertised anywhere near £45 is not undercutting the market. It is telling you through arithmetic that the contents do not match the label. The full market comparison sits in our retatrutide price UK index.
How the Triple Receptor Mechanism Works
Retatrutide is a triple receptor agonist, and that is what separates it from everything else in this category. It acts at the GLP-1 receptor, the GIP receptor and the glucagon receptor simultaneously. Semaglutide targets one of those, tirzepatide targets two, and the glucagon component is the addition unique to retatrutide.
The practical significance is in the direction of effect. GLP-1 and GIP activity reduces energy intake, while glucagon receptor activity raises energy expenditure. Combining both sides of the energy balance equation in a single molecule is the reason the compound attracted attention, and it is why the published results exceeded those reported for the dual agonists. Our reta peptide guide covers the receptor pharmacology in more depth.
Mapping 20mg Against the Trial Schedules
A single retatrutide 20mg pen spans a meaningful period at the amounts actually studied, which is the practical case for choosing it over anything smaller.
| Weekly amount from the trials | Weeks covered by one 20mg pen |
|---|---|
| 1mg | 20 |
| 2mg | 10 |
| 4mg | 5 |
| 8mg | 2.5 |
| 12mg | 1.67 |
The Phase 2 obesity study published in the New England Journal of Medicine randomised participants to target amounts of 1mg, 4mg, 8mg and 12mg weekly, every one reached through stepped escalation rather than started at target. Phase 3 work is registered on ClinicalTrials.gov. The complete schedules and escalation intervals are in our dosage chart guide.
The Pen Device and Dial Accuracy
The dial mechanism decides how finely a protocol can be followed, and it is worth confirming before ordering rather than after. A coarse device cannot be made fine. Prime the pen exactly as its instructions specify on first use, because an unprimed pen delivers less than the dial indicates and quietly distorts every measurement taken from it.
- Confirm the increment per click matches the amounts your work actually requires.
- Prime before the first delivery, every time a new pen is opened.
- Record what was delivered rather than what was dialled.
- Treat any figure from an unprimed first delivery as unreliable and exclude it.
- Use a fresh needle for every draw to avoid contaminating the cartridge.
Device mechanics across formats are compared in our retatrutide pen guide.
Storage and Cold Chain Requirements
Retatrutide 20mg ships as a solution, and peptides in solution degrade. Handling decides whether the pen still matches its label at the point of use, and no amount of branding substitutes for it.
- Refrigerate between 2 and 8 degrees on arrival and never freeze, since freezing denatures the peptide as reliably as heat does.
- Keep the pen in its original carton, away from direct light.
- Avoid repeated temperature cycling. Several short excursions cause more cumulative damage than one steady period slightly out of range.
- Log the batch number and arrival condition on the day it lands, not later from memory.
- Treat a pen that arrives warm as compromised. Refrigerating it afterwards reverses nothing.
How We Document Each Batch
Every retatrutide 20mg pen we ship carries a printed batch number on the device itself, not only on the outer carton, so the unit remains identifiable once the packaging is discarded. The certificate of analysis for that specific batch names the issuing laboratory and the test date rather than reproducing a generic template.
That distinction matters more than it sounds. Purity above 98 percent is claimed across this entire market, and purity says nothing about content. A high purity figure on an underfilled pen is not reassurance, which is why fill volume and concentration are both stated so the total can be confirmed arithmetically.
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Retatrutide 20mg Against the Other Formats
| Format | Price | Cost per mg | Best for |
|---|---|---|---|
| 10mg pen | £80 to £110 elsewhere | £8.00 to £11.00 | Nothing we recommend |
| Retatrutide 20mg | £139.99 | £7.00 | First order and shorter work |
| 40mg kit | £220 | £5.50 | Extended work, best value |
We do not stock the 10mg format because it carries a structural per milligram penalty with no offsetting benefit, and the reasoning is set out in full in our retatrutide 10mg guide. If you are comparing labels rather than sizes, the VLS pen guide and the Viogen guide explain what a brand name does and does not prove.
Ordering, Delivery and Handling on Arrival
Orders ship from the United Kingdom in insulated packaging with a coolant pack. Refrigerate on arrival, check the batch number against the paperwork, and record the condition the parcel arrived in. If anything looks wrong, contact us before opening the device rather than after.
Supplier checks worth running before any peptide order, from us or anyone else, are set out in our buy retatrutide UK guide. Everything currently in stock is on the shop page.
What the Phase 2 Results Actually Showed
The figure quoted everywhere is a mean weight reduction of 24.2 percent at 48 weeks in the highest amount arm. It is a real result from a randomised controlled trial, and it is also routinely stripped of the context that makes it interpretable, so it is worth restating properly here.
That figure came from the 12mg weekly arm, reached through stepped escalation over months rather than started at target. Lower arms produced proportionally smaller reductions. Discontinuation was meaningful across the higher arms and those participants are part of the same dataset, not a footnote to it. Most importantly, no published follow up has reported what happens after stopping, which remains the single largest gap in the evidence base.
Gastrointestinal events dominated the reported burden and clustered around escalation steps rather than running at a constant rate through the study. A modest amount related heart rate increase was also observed. The full breakdown, including the trial exclusion criteria that limit how far these figures generalise, is in our Phase 2 trial analysis and our side effects guide.
Retatrutide 20mg Compared With the Dual and Single Agonists
We stock all three generations of this compound class, and the differences are pharmacological rather than promotional.
| Compound | Receptors targeted | Our format | Price |
|---|---|---|---|
| Semaglutide | GLP-1 only | 8mg pen kit | £160 |
| Tirzepatide | GLP-1 and GIP | 40mg pen kit | £180 |
| Retatrutide | GLP-1, GIP and glucagon | 20mg pen | £139.99 |
Semaglutide and tirzepatide both have licensed counterparts prescribed in the UK, which means their clinical profiles are far better characterised. Retatrutide has no licensed counterpart anywhere in the world and remains in Phase 3. That is a meaningful difference in evidence maturity, and anyone choosing between them for research purposes should weigh it deliberately rather than assuming newer means better. Our retatrutide versus Mounjaro comparison works through the trial data side by side.
Keeping a Defensible Research Log
Whatever the work, a record made at the time is worth more than a reconstruction afterwards, and it is the part most often skipped. For each retatrutide 20mg pen, capture the following on the day it arrives and each time it is used.
- Batch or lot number as printed on the device, cross checked against the certificate of analysis.
- Arrival date, packaging condition and whether the coolant pack was still cold.
- Storage location and the temperature range it has been held at.
- Priming performed, and the amount discarded to prime.
- Each amount delivered, with the date, rather than each amount dialled.
- Any deviation, including a missed refrigeration period, however short.
Peer reviewed background literature on this compound class is indexed on PubMed if you are building a protocol around published work rather than starting from a supplier claim.
Legal Position and Research Use Only
Retatrutide holds no marketing authorisation from the MHRA. It is not a licensed medicine in the United Kingdom, cannot lawfully be supplied for human use, and cannot be advertised with therapeutic claims under Advertising Standards Authority rules. This retatrutide 20mg pen is supplied for laboratory research use only and is not for human or veterinary consumption.
The published evidence comes from controlled clinical trials of pharmaceutical grade material under supervision, and does not transfer to research material used outside that setting. Anyone seeking treatment for obesity or type 2 diabetes should speak to a registered UK prescriber about licensed options. Nothing on this page is medical advice.
Retatrutide 20mg FAQ
How much does retatrutide 20mg cost?
£139.99 per pen, which is £7.00 per milligram and sits inside the normal UK range of £6.00 to £9.00 per milligram for this format.
How long does a retatrutide 20mg pen last?
Against the published trial schedules it covers 20 weeks at 1mg weekly, 10 weeks at 2mg, 5 weeks at 4mg and 2.5 weeks at the 8mg amount studied in the upper arms.
Is retatrutide 20mg better value than the 40mg kit?
The 40mg kit is better value at £5.50 per milligram against £7.00. The 20mg pen is the better choice for a first order or shorter work where committing to a larger quantity is not warranted.
What purity is it?
Above 98 percent, documented per batch with the issuing laboratory and test date named on the certificate of analysis.
How should it be stored?
Refrigerated between 2 and 8 degrees, never frozen, in the original carton away from direct light, without repeated temperature cycling.
Is retatrutide legal in the UK?
It can be supplied for laboratory research use only. It holds no MHRA authorisation, is not a licensed medicine, and cannot lawfully be sold or supplied for human use.
Why is a cheap retatrutide 20mg pen a warning sign?
Production and refrigerated handling impose a hard cost floor. A price far below roughly £3 per milligram usually indicates underfill, a substituted peptide, or no active compound at all.
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