Retatrutide vs Mounjaro: Which Weight Loss Treatment Is Right for You?

Retatrutide is a weight loss injection currently undergoing clinical trials that has shown promising outcomes. It's popular because studies suggest it may outperform Mounjaro in weight-loss results. For this reason, many people are wondering which is the better option: Mounjaro or retatrutide.

Retatrutide has not yet received approval for use in the UK. Mounjaro, on the other hand, is approved for weight loss and available through government and private providers. Therefore, the better option for real-world use is currently Mounjaro because it's the only one that is legally available.

This guide explains the differences between Mounjaro and Retatrutide, what clinical results show, their side effects, and who each treatment may suit.

Retatrutide vs Mounjaro Quick Comparison

What Is Retatrutide?

Retatrutide is a weight loss medication currently undergoing Phase 3 clinical trials. The medicine was developed by Eli Lilly, the same company that makes Mounjaro. Retatrutide is a triple agonist, which means it acts on three hormone receptors that help control appetite and metabolism. It's why some people call the injection 'Triple G.'

How It Works

Retatrutide targets:

• GLP-1: Helps suppress appetite and supports insulin response.
• GIP: Works alongside GLP-1 to improve blood sugar control and may contribute to fat metabolism.
• Glucagon: Increases energy expenditure and may encourage fat burning by prompting the body to use stored energy more efficiently.

Available weight loss injections target one or two of these receptors. Retatrutide is the first one to combine all three mechanisms into a single weekly injection.

Retatrutide Clinical Trial Results

According to the Phase 2 trial results published in the New England Journal of Medicine, participants taking the highest dose of retatrutide achieved an average weight loss of about 24% in 48 weeks. The participants also noted improvements in blood sugar and cardiometabolic risk factors.

These results are higher than any weight loss drug currently approved in the market, which is why triple G has received a lot of attention. It suggests that retatrutide could be the most effective obesity treatment. However, phase 3 trials must conclude to confirm use and long-term safety data.

Who May Receive Retatrutide in Future?

The Medicines and Healthcare products Regulatory Agency (MHRA) is the body responsible for approving new medicines in the UK.

If retatrutide receives regulatory approval, it will most likely be for weight management in adults who are:

• Overweight (BMI of 27–29.9) with at least one weight-related comorbidity such as sleep apnoea.
• Living with obesity (BMI of 30 or higher).

The exact eligibility requirements will depend on the final prescription guidance.

What Is Mounjaro?

Mounjaro, or tirzepatide, is a once-weekly prescription weight loss injection developed by Eli Lilly. It's licensed and available in the UK for eligible patients.

How It Works

Tirzepatide targets two hormone receptors: GLP-1 and GIP. It doesn't activate glucagon receptors and is therefore a dual agonist. These naturally occurring hormones help:

• Reduce appetite
• Slow digestion so you feel fuller for longer
• Regulate blood sugar levels
• Improve insulin response
• Reduce food cravings

Mounjaro is licensed for improving blood sugar control in adults with type 2 diabetes. It's also prescribed for weight management in eligible adults living with obesity or overweight with weight-related health conditions.

People taking Mounjaro as part of their treatment must also eat a healthy diet and exercise regularly.

How Much Weight Can You Lose on Mounjaro?

According to the SURMOUNT-1 study, people who received the highest dose lost about 22.5% of their starting body weight after 72 weeks. However, note that your average loss may differ depending on treatment consistency, response to the medication, lifestyle changes, and starting weight.

Reta vs Mounjaro: Key Differences

While retatrutide and tirzepatide help with weight loss, the medications work differently and have varied effects. The following are the main differences between the two:

1. Mechanism of Action

Mounjaro targets two receptors, while retatrutide has triple action.

Both medications help regulate blood glucose and appetite, which can help you feel less hungry. This eventually causes you to eat less, leading to weight loss.

Researchers believe that stimulating the glucagon receptors can increase calorie burning, which may explain why triple G has higher weight loss results so far. However, ongoing TRIUMPH Phase 3 clinical trials will provide more information on the medication's effectiveness.

2. Weight Loss Results

The SURMOUNT-1 trial showed participants losing about 22.5% of their starting body weight after 72 weeks on the highest dose of Mounjaro. Retatrutide's Phase 2 trial shows higher results, about 24% of body weight.

Note that these results are from different studies, not a direct comparison trial.

3. Blood Sugar Effects

Both medications improve blood sugar control. GLP-1 and GIP work together to regulate blood glucose levels by improving insulin secretion and reducing glucagon release after meals. However, Mounjaro has stronger evidence because it's licensed for treating type 2 diabetes.

4. Side Effects

Mounjaro and retatrutide have similar effects on the digestive system. The most common symptoms include:

• Nausea
• Vomiting
• Diarrhoea
• Constipation
• Stomach discomfort

These side effects are the most intense when starting treatment and during dose increases as the body adjusts.

Researchers are still evaluating long-term and potential rare side effects in ongoing trials for retatrutide. Similarly, the long-term side effects of Mounjaro are still under study.

5. Availability

Retatrutide has not received MHRA approval. You cannot legally get a prescription for the medication through UK pharmacies or clinics. Buying retatrutide online in the UK is considered unsafe and illegal. The only way to get the injection is through regulated clinical trials.

Patients who want effective weight loss medications now can use Mounjaro. The injection is licensed for use in the UK. However, you should only buy Mounjaro from regulated and approved sources such as Curely.

Avoid people who:

• Sell Mounjaro without a prescription or consultation.
• Aren't registered with the General Pharmaceutical Council (GPhC) (or the PSNI in Northern Ireland).
• Have unusually low prices or bulk deals that are much cheaper than market rates.
• Have no access to a clinician or healthcare practitioner.

6. Cost

Retatrutide is still undergoing clinical trials, so there's no information on how much it will cost after approval.

Mounjaro is available through the National Health Service (NHS) with a standard prescription charge of £9.90 per item in England. However, some residents (e.g., those aged 60 and over or people with low income) are exempt from the fee and can access the medication for free.

Also, residents of Scotland, Wales, and Northern Ireland don't pay for NHS prescriptions, meaning the injection is free.

Currently, the NHS has a long waitlist for Mounjaro. According to a news article by the BBC, parts of the UK have waitlists of up to 10 years. It's why some people choose to go through private channels.

Price comparison for Mounjaro in different clinics shows it costs about £140 to £260+ per month, with Curely offering some of the best prices.

Should You Wait for Retatrutide?

Because triple G is considered a game changer for the weight loss industry, some people are considering waiting until the medication receives approval. However, this may not be the right move for everyone, depending on your health and how urgently you need to lose weight.

Reasons to Wait

• You're already participating in a clinical trial.
• You're only interested in future treatment options.
• You're happy delaying treatment while more evidence becomes available.
• You want to save up for the medication.
• You're planning a pregnancy.

Reasons Not to Wait

Delaying treatment for some people may not be the best choice.

Obesity is a chronic medical condition that can increase the risk of heart disease, sleep apnoea, high blood pressure, and type 2 diabetes. Waiting for a medication that may take a long time to receive approval means increasing the risk of developing these conditions.

Mounjaro is approved for managing obesity, and many patients notice meaningful improvements in body weight and overall wellbeing. Some specialists recommend choosing an approved treatment that's available now rather than delaying treatment for a medicine that's still undergoing regulatory assessment.

The best option is to do what your doctor recommends.

Your Weight Loss Journey Starts with Curely

As a registered online UK clinic and pharmacy, we provide convenient access to weight loss services under medical supervision.

Our process starts with an online consultation that covers your medical history and overall health. This helps us determine the best treatment for you.

Curely has weight loss pills such as the newly approved Wegovy pill. We also offer injections such as Mounjaro and Wegovy. Once you choose the ideal medication, we'll deliver it to your door in discreet packaging because your privacy is important to us.

Start your weight loss journey today with Curely.

FAQs

Is Retatrutide Stronger Than Mounjaro?

Research so far shows retatrutide has impressive weight loss results of about 24%, which is higher than Mounjaro's 22.5%. However, there are no direct comparison studies of the two medications. Also, triple G is still undergoing clinical trials. Therefore, it's too soon to say whether the medication is stronger.

Is Retatrutide Approved in the UK?

No. Retatrutide is still undergoing Phase 3 clinical trials and has not received approval from the MHRA. It isn't available through UK pharmacies or private prescribers outside regulated studies. Visit Curely's website to access approved weight loss treatments in the UK.

Can I Switch from Mounjaro to Retatrutide?

Not yet. Since retatrutide isn't licensed for use in the UK, you cannot switch. If it becomes available in the future, your healthcare professional will advise on changing treatments.

Is Retatrutide Safe?

Current trial data show promising results. However, researchers are still gathering safety information through clinical trials.

Final Thoughts

Retatrutide and Mounjaro are medications that can help with weight loss in eligible adults. However, they are different.

Retatrutide works on three receptors, and so far, the results are higher than any other GLP-1 medication. However, it's still undergoing clinical trials.

Mounjaro, in contrast, is licensed for use in the UK, with many patients seeing significant improvement in weight and overall health. It works on two hormones and is a good choice for eligible adults who need treatment now.

Curely offers a simple online consultation to assess your eligibility for Mounjaro and other approved weight loss medications. Reach out today for more information on accessing treatment.

Reference List

• Buckland C. NHS weight-loss jab wait lists reach 10 years in Wales. BBC. May 2, 2026.
• Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine. 2022;387(3):205-216.
• Jastreboff AM, Kaplan LM, Frias JP, et al. Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. The New England Journal Of Medicine. 2023;389(6).
• Lilly E. Lilly’s Triple Agonist, Retatrutide, Delivered Powerful Weight Loss in Pivotal Phase 3 Obesity Trial. Eli Lilly and Company. 2025.