Is Retatrutide Better Than Mounjaro? UK Facts (October 2026)

01 · The verdict

Is retatrutide better than Mounjaro? The verdict for UK patients

No, not in any way you can act on in the UK. A medicine can only be better for you if it is licensed, prescribed after a proper assessment and supplied through a regulated route. Retatrutide meets none of those tests, whereas Mounjaro meets all of them.¹

Mounjaro is the brand name for tirzepatide, a once-weekly injection made by Eli Lilly. In the UK it is licensed for weight management in adults and for type 2 diabetes.¹ Retatrutide, by contrast, is an unlicensed "research" peptide in the UK, and we do not supply it.⁷

Our deeper look at retatrutide's claims versus tirzepatide covers the same ground from another angle.

02 · Side by side

Retatrutide vs Mounjaro at a glance

Never read the trial rows as a race between two columns. Different trials in different populations cannot be set side by side. Only SURMOUNT-5 supports a direct tirzepatide-versus-semaglutide comparison.

03 · Decision factors

Who each option suits

Mounjaro suits adults who want a licensed, prescriber-supervised weight-management injection now. Our Mounjaro pen comes in all six strengths, and all six doses are in stock.

Retatrutide "suits" nobody in the UK as a treatment today, because there is no licensed route to it. If you are tempted by it, the useful question is not which is better but what you would be injecting, who made it, and who would be responsible if something went wrong. With an unlicensed research peptide, the honest answer to the last two is: nobody you can identify.

04 · What Mounjaro offers

What Mounjaro delivers, in published evidence

Mounjaro's results come from published, peer-reviewed trials of the licensed product. That is the main reason it is the sensible benchmark in this comparison.

In SURMOUNT-1, a trial of 2,539 adults, people taking tirzepatide alongside diet and exercise lost on average 15% of their body weight on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks, compared with 3.1% with lifestyle changes alone.² For someone starting at 100 kg, 20.9% is about 21 kg. These are trial averages, and individual results vary. Treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.²

At 72 weeks, 85% of participants on 5mg, 89% on 10mg and 91% on 15mg had lost at least 5% of their body weight. Half of participants on 10mg and 57% on 15mg lost at least 20%.²

SURMOUNT-5 was the first large head-to-head trial against semaglutide. Adults on tirzepatide lost on average 20.2% of body weight over 72 weeks versus 13.7% on semaglutide 2.4mg (Wegovy). Both are effective, licensed treatments, and which suits you depends on your health profile, tolerance and prescriber advice rather than the headline number alone.¹⁵

Tirzepatide is the first treatment of its kind to activate two natural gut-hormone receptors at once, GIP and GLP-1. Together they help regulate appetite, slow how quickly the stomach empties and improve the way the body responds to insulin. Most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet.¹

05 · Why retatrutide is unlicensed

What are the risks of taking retatrutide?

The main risk is that no one can tell you what is in the vial. Retatrutide has no UK licence, so products sold under that name are unlicensed "research" peptides, with no regulated supply chain and no safety data for use in people.

That has practical consequences:

• Unknown contents. Without a regulated supply chain, there is no assurance of what the product contains, how strong it is or how it was stored. The MHRA publishes counterfeit medicine alerts for exactly this reason.⁷
• No prescriber oversight. A licensed medicine is started, titrated and reviewed by a prescriber. A research peptide bought online has none of that.
• No safety data for combinations. Mounjaro must not be combined with other GLP-1 medicines, unlicensed research peptides such as retatrutide, or compounded copies. These combinations have no safety data and no regulated supply chain.
• Reporting side effects. Suspected side effects can be reported through the MHRA Yellow Card scheme.¹⁹

If a seller promises faster results outside a licensed pathway, that is the warning sign. A seller offering to supply without a consultation or prescription is another.

06 · Why the headline numbers mislead

Why "how much better" has no honest answer yet

Trial results depend on who was enrolled, how long the trial ran, what dose was reached and how people were supported. The first large head-to-head trial of tirzepatide against another weight-loss medicine is SURMOUNT-5, against semaglutide.¹⁵ There is no UK-verifiable head-to-head of retatrutide against Mounjaro, so any "X% better" claim is a comparison of different studies.

Averages also hide the spread. Even within SURMOUNT-1, results varied widely. Some participants lost at least 20% of body weight on 15mg and others lost less.² Trial averages do not predict your own result.

Weight is also only one outcome. Tolerability, how easy treatment is to stay on, your other conditions and the quality of follow-up matter as much as a maximum percentage, and for an unlicensed product none of these has been properly established for UK use.

07 · Common questions about using it

Week 1, injection sites, food and muscle on Mounjaro

There is no UK product information for retatrutide; for Mounjaro, follow your prescriber's guidance and the patient information leaflet. Guidance written from forums or seller pages is not a safe substitute.

• Timing and injection. Mounjaro is a once-weekly injection in a pre-filled KwikPen.¹ Inject under the skin once a week, on the same day each week, into the stomach area (at least 5cm from the belly button), the front of the thigh, or the back of the upper arm if someone else gives the injection, rotating the site with each dose.¹³ Needles, a sharps bin and injection guidance come with every order.
• What to eat. Treatment is used alongside a reduced-calorie diet and increased physical activity.² Most people feel fuller sooner and less hungry between meals, which supports eating less.¹ Your prescriber can advise on your own plan.
• How fast it works. Trial averages are measured over 72 weeks, not days. Individual results vary.
• Muscle and visceral fat. Ask your prescriber how to protect muscle during weight loss.

New symptoms on any medicine should be discussed with your prescriber and can be reported through the Yellow Card scheme.¹⁹ Seek immediate medical help for severe, persistent stomach pain that may spread to your back, with or without vomiting (possible pancreatitis); pain in the upper right abdomen, fever or yellowing of skin/eyes (possible gallbladder problems); or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing.

08 · Should you switch or wait?

Should I switch from tirzepatide to retatrutide, or wait for it?

Do not switch to an unlicensed peptide. There is no licensed UK pathway to switch onto, and Mounjaro must not be combined with retatrutide or other research peptides.⁷ If you are already on Mounjaro and doing well, you have a licensed, supervised treatment with a clear dose ladder from 2.5mg to 15mg.¹

Waiting is a more reasonable question. If you are thinking of waiting, a prescriber can assess whether a licensed treatment suits you now.

If Mounjaro is not right for you, other licensed options exist, and a prescriber can help you choose. Our guides compare Mounjaro with Rybelsus, metformin, Trulicity and orlistat. You can also browse all weight loss treatments.

09 · NHS or private access

Getting a licensed treatment: NHS or private

Mounjaro is available on the NHS, but access is being phased in over several years. NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition, and the NHS primary-care rollout began in June 2025 with the highest-need groups first (initially BMI 40+ with four or more qualifying conditions).⁴⁶ Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment rather than waiting.

If you go private, the regulated route is the point. A GPhC-registered pharmacy dispenses genuine pens after a prescriber has reviewed your health information. That is the opposite of buying a vial from a website with no consultation.

10 · What Mounjaro costs

What Mounjaro costs compared with the risk of cheaper alternatives

Part of retatrutide's appeal is price. Across the UK pharmacies we track, Mounjaro pens range from £143.96 to £339.00 per month depending on dose and provider (checked 11 October 2026). The cheapest and dearest 2.5mg starting pens run from £143.96 to £179.99.

At EverydayMeds, your first 2.5mg pen costs £129.99 with code FIRST40 (standard price £169.99). Switching to us at 15mg? Your first order is £289.99. After that, every later order is £25 off the standard price (code DOSE25).

Standard monthly prices for each strength are £169.99 at 2.5mg, £218.99 at 5mg, £279.99 at 7.5mg, £290.99 at 10mg, £319.99 at 12.5mg and £329.99 at 15mg, all before discounts. If you step up after 4 weeks on each dose, your first four pens (2.5mg to 10mg) cost £959.96 at standard prices. A first year costs £2,711.88 if you settle at 5mg, up to £3,599.88 at 15mg, again before discounts; a new customer's first order is £40 less.

A cheap unlicensed vial may look like better value. But a product with unknown contents and no oversight is not a cheaper version of the same thing. Consultation with us is free, and the price shown is the price paid.

11 · How ordering works

How to start Mounjaro with us

Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full.

• Free online consultation. A short health questionnaire, no charge and no obligation. Start your free consultation.
• Prescriber review. Your answers are reviewed by a GPhC-registered prescriber, not a scoring script. Unsuitable orders are refunded automatically.
• Dispensing and delivery. Our registered pharmacy dispenses genuine KwikPens sourced through official LillyDirect supply. Same-day dispatch applies when you order by 3pm, with free next-day tracked delivery in temperature-controlled packaging. Saturday delivery is £14.99.

Ongoing monthly reviews, dose-titration and side-effect support are included, and repeat orders re-check suitability with no auto-shipping. There are no subscriptions; Klarna and pay-monthly options are available.

Mounjaro (tirzepatide) is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber. It is used alongside a reduced-calorie diet and increased physical activity. Individual results vary. This page is information, not a substitute for medical advice.