Retatrutide: The New Triple-Agonist Weight Loss Treatment

Retatrutide is the latest weight loss medication that’s currently in phase 3 clinical trials. It contains the active ingredient, retatrutide, and is being developed by the same manufacturer as Mounjaro, Eli Lilly, for the management of obesity and type 2 diabetes. Retatrutide is a triple agonist, targeting the receptors of 3 hormones that can impact appetite, weight, and blood sugar levels, earning it the nicknames the “triple-G” and the “Godzilla” of weight loss jabs.

Retatrutide is not yet available in the UK and has not been approved for use by any regulatory bodies – it is still undergoing clinical trials to assess its safety and effectiveness.

In this guide, you can find out more about how retatrutide works, what the latest research says, the potential side effects, and how it compares to other popular weight loss injections, such as Mounjaro and Wegovy.

Retatrutide is a triple agonist that targets the receptors of 3 hormones, mimicking their effects to improve blood sugar levels and promote weight loss. The 3 hormones are:

By mimicking the effects of these hormones, retatrutide helps you lose weight by suppressing your appetite, slowing digestion, and helping your body break down fat more effectively. Because of this, retatrutide is thought to be more effective than Wegovy, which only binds to GLP-1 receptors, and Mounjaro, which is a dual agonist that mimics the effects of GLP-1 and GIP.

Retatrutide is currently in phase 3 clinical trials for weight loss, but results from phase 2 trials are promising. At the highest weekly 12mg dose, participants lost an average of 24.2% of their starting body weight over 48 weeks. Within this group, 26% of people also lost at least 30% of their initial body weight.

A lower 4mg weekly dose also resulted in impressive weight loss results, with an average loss of 17% over 48 weeks and:

• 92% of participants lost at least 5% of their starting body weight
• 75% lost at least 10% of their body weight
• 60% lost at least 15% of their starting weight

Retatrutide vs Mounjaro

In clinical trials, the active ingredient in Mounjaro, tirzepatide, results in an average weight loss of 22.5% at the highest 15mg per week dose over 72 weeks. Unlike retatrutide, tirzepatide only binds to 2 hormone receptors, GLP-1 and GIP, and is available with a prescription for weight management and type 2 diabetes.

Retatrutide vs Wegovy

Wegovy contains the active ingredient semaglutide, a GLP-1 receptor agonist that slows digestion, suppresses appetite, and regulates blood sugar levels. At the maximum maintenance dose of 7.2mg per week, Wegovy can help you lose on average 21% of your initial body weight over 72 weeks.

In phase 2 clinical trials, retatrutide was given in the following doses:

• 1mg, 2mg or 4mg (starting dose)
• 1mg, 4mg, 8mg or 12mg per week (maintenance dose)
• 12mg per week (maximum dose)

The dose escalation was similar to other weight loss medications, with the retatrutide dose increasing every 4 weeks.

However, there is no ‘official’ retatrutide dosage schedule yet because it’s still being researched for its effects on weight loss. Like other weight loss injections, retatrutide was started at a low dose and gradually increased over several weeks, to allow the body to get used to the medication and minimise the chance of side effects.

If retatrutide is approved for weight loss, the dosage schedule will be confirmed, and it will only be available with a prescription. You will also need to meet specific criteria before a doctor will approve it for you.

Is retatrutide an injection?

Yes, retatrutide will be available as a once-weekly self-injectable medication, similar to other weight loss injections. Although the official dosage schedule is not yet known, it will likely start at a low dose and increase gradually until you reach the maximum maintenance dose. This will help the body get used to the active ingredient and lower the chance of side effects.

Retatrutide side effects are similar to Wegovy and Mounjaro, with mild to moderate gastrointestinal side effects most commonly reported. They include:

• feeling or being sick
• diarrhoea
• constipation

These side effects are more likely to occur when the treatment first starts or when the dose increases. Most are likely to be managed easily at home by:

• eating smaller, more frequent meals
• avoiding spicy, greasy, or fatty meals
• eating plain, bland foods, like toast and crackers
• drinking frequent sips of water to prevent dehydration
• getting rest until you feel better
• drinking peppermint or ginger tea if you feel sick

7% of trial participants also reported changes in skin sensation, such as tingling or sensitivity, but these were not severe and did not cause anyone to stop the treatment.

The long-term safety data for retatrutide is currently limited, but a full list of side effects will be made available once the medication has completed testing and been approved. A list of known possible side effects will always be available in the patient information leaflet.

Mounjaro is an approved medication for weight loss and type 2 diabetes in the UK, while retatrutide is still in development and currently going through phase 3 clinical trials. Mounjaro attaches to the receptors of 2 digestive hormones, while retatrutide also attaches to these and glucagon receptors, which could mean it has a stronger effect on weight loss.

Retatrutide is not yet available in the UK and is unlikely to be approved before 2027. It is still going through phase 3 clinical trials, which are assessing the safety and effectiveness of retatrutide for weight loss. These are due to finish in May 2026.

After the trial results are published, the Medicines and Healthcare products Regulatory Agency (MHRA) will need to review the drug's safety and effectiveness data. This will then be used to decide whether it will be approved for weight loss in the UK.

If retatrutide is approved, it will likely be available privately first from online doctor services, like Superdrug Online Doctor, who offer weight loss services. It may take longer to become available on the NHS because the NHS has its own regulations that a medication must meet before it is approved.

How much will retatrutide cost?

The expected cost of retatrutide is not yet known, but it is likely to be similar to other weight loss injections. The closest medication currently available on the market to compare is Mounjaro. Mounjaro prices start from around £195.00 a month for the lowest dose, and around £370.00 for the highest dose, depending on the service provider and any offers they may have on at the time of ordering.

Once retatrutide has been approved in the UK, the price will be confirmed.

Is retatrutide available on the black market?

Yes, there are reports of black market versions of retatrutide being available that may be sold through online social media channels and websites falsely labelling it as “for research purposes only”. However, getting retatrutide through these sources is illegal and highly dangerous.

The unauthorised products may be counterfeit and contain unknown, toxic, and potentially dangerous ingredients.