What is Retatrutide (Triple G)?

Wednesday, March 5, 2025

Eli Lilly has developed Retatrutide, a new weight loss medicine. As the only injection to support weight loss in three ways, Retatrutide could be revolutionary in this space. It is still in development, so does not yet have a brand name.

How does Retatrutide work?

Retatrutide has been nicknamed ‘Triple G’. This is because it targets three different receptors and hormones - GLP-1, glucagon and GIP (1). Glucagon and GIP are naturally released when you eat food, and play a role in reducing appetite, lowering blood sugar, and helping the body burn fat (1).

This means Retatrutide can support people to reduce weight in three ways:

Suppress appetite and slow digestion, meaning you’re not as hungry as often and feel fuller for longer
Increase fat metabolism, so your body breaks down fat quicker
Increase insulin sensitivity, which reduces blood sugar, causing the body to break down stored fat

What does Retatrutide treat?

Retatrutide has been predominantly developed for weight loss for people with obesity and is proving promising (1).

It might also be used to treat type 2 diabetes. With type 2 diabetes, a person’s insulin either doesn’t work properly, or there is not enough of it, causing blood sugar levels to become too high (2). This can cause individuals to feel tired and thirsty, lose weight unintentionally, and need to pee more than usual (2).

Some people can also experience blurred vision, slower healing of cuts and wounds, thrush that keeps coming back, or itching around the penis or vagina (2). Since Retatrutide targets glucagon receptors, increasing insulin sensitivity and reducing blood sugar, it could be an effective treatment for people with type 2 diabetes (1).

Investigations into Retatrutide’s effectiveness in fatty liver disease are also underway. Non-alcoholic fatty liver disease (NAFLD) is a term that covers several conditions that are caused by fat building up in the liver (3).

This usually affects people who are overweight or living with obesity, or who have type 2 diabetes (3). NAFLD can cause the liver to become inflamed, which can lead to scarring and damage, and then even liver failure (3). Since Retatrutide may be able to reduce liver fat in people with obesity, it could also prevent the progression of NAFLD (2).

Is Retatrutide better than Wegovy and Mounjaro?

Currently, Wegovy and Mounjaro injections are available to support weight loss.

Whilst Wegovy targets GLP-1 and Mounjaro targets GLP-1 and GIP (4), neither target glucagon receptors. This means that retatrutide, with three targets, could be more effective (1).

Testing has already shown that Retatrutide can help participants lose more weight in a shorter amount of time (1). Studies show that Retatrutide has achieved 24% weight loss in less than a year (48 weeks) (1). This is the highest percentage weight loss ever recorded in a trial for an obesity drug.

Over a longer period of time (72 weeks), Mounjaro has shown a 22% loss in weight, and Wegovy has shown 17% (4). This is also more than another upcoming injection, CagriSema, which has shown 23% weight loss in over a year (68 weeks) (5).

How is Retatrutide administered?

Retatrutide is given using a pen injector (1). It is delivered as a subcutaneous injection into the arm, thigh, or stomach (1). It is expected to be administered weekly, starting with a lower dose to minimise side effects (1).

What are the side effects of retatrutide?

Retatrutide has some common side effects (1), similar to Wegovy and Mounjaro, including:

Nausea
Vomiting
Constipation
Diarrhoea

Since retatrutide can help increase weight loss in an additional way to Wegovy and Mounjaro, these side effects could be more intense (1). They can be managed by using the injection when you eat, drinking plenty of water, and getting enough fibre in your diet (6).

You should always speak to your doctor if you are experiencing any side effects from medication. They can help you manage side effects or suggest a different treatment.

When will Retatrutide be available?

Whilst Retatrutide has shown promising results in clinical trials, it will not be available straight away. As a new drug, it will take a while to get through all the stages of testing.

This is important for safety, we must understand how it works, the side effects, and how it compares to other treatments. Retatrutide is currently in the latter stages of clinical trials (Phase 3), if it continues to do well, it could be available by 2027 (7). It will be licensed as a prescription-only drug so will not be available over-the-counter.

In the UK, the Medicines and Healthcare products Regulatory Agency (MHRA) must review the trial data before they approve any drug (8). At this point, the drug will then be privately available. To be made available on the NHS (or Health and Social Care, in Northern Ireland), it will need to be approved by a government organisation (9):

England - National Institute for Health and Care Excellence (NICE)
Scotland - Scottish Medicines Consortium (SMC)
Wales - All Wales Medicines Strategy Group (AWMSG)
Northern Ireland - Department of Health, Social Services and Public Safety (DHSSPS)

This process can take several months or even years, but it is important that drugs and medicines are checked for safety and effectiveness.

How much will Retatrutide cost?

The price of Retatrutide is not yet known. Since it is set to compete with Wegovy and Mounjaro, it will likely cost a similar amount when it launches.

At the moment, starting injection prices are in the range of £130 to £230 for Wegovy (10) and Mounjaro (11).