What is retatrutide? How it works, availability, & more

GLP-1 medications are well known for their impressive weight loss results. But a new drug, retatrutide, may be even more powerful than the currently approved meds. In fact, in clinical trials, the experimental injection led to an average weight loss of up to 23%–26% in ~one year. 

So, how does retatrutide work, and when can you get your hands on it? Read on to find out.

Retatrutide is a new drug being developed by Eli Lilly, the manufacturer of Mounjaro and Zepbound. It’s currently being studied for weight loss and type 2 diabetes, with some similarities to orforglipron, another drug developed by Eli Lilly. 

Like other GLP-1 weight loss injections, retatrutide is injected subcutaneously (under the skin) once a week. But it stands out from other GLP-1s because it’s a triple-hormone receptor agonist. 

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As a triple-hormone receptor agonist, retatrutide works by mimicking three hormones naturally found in the body. These include:

• Glucagon-like peptide-1 (GLP-1). GLP-1 increases fullness by slowing down digestion, regulates blood sugar by boosting insulin and inhibiting glucagon, and reduces appetite by targeting parts of your brain that manage fullness and food cravings. This is the hormone that semaglutide drugs, such as Wegovy and Ozempic, target. 

• Glucose-dependent insulinotropic polypeptide (GIP). GIP is another hormone that regulates blood sugar and can reduce appetite. When combined with GLP-1, as it is in drugs like tirzepatide (Mounjaro, Zepbound), it enhances GLP-1’s effects on weight loss and type 2 diabetes. 

• Glucagon (GCG). This hormone revs up your metabolism, suppresses appetite, and directs your body to burn fat for energy. It also tells your body to produce new sugar. But since retatrutide also includes GIP and GLP-1, the medication keeps it from overdoing it on sugar production to avoid causing high blood sugar (hyperglycemia).

Studies have shown that GLP-1/GIP dual-receptor drugs like tirzepatide produce more weight loss than single-receptor GLP-1s like semaglutide. By adding glucagon into the mix, a GIP–GLP-1–GCG triple receptor agonist like retatrutide may lead to even more weight loss.

Studies suggest retatrutide can lead to more weight loss — and in less time — than any of the currently approved weight loss medications. In fact, people who took retatrutide lost up to 24%-26% of their weight after 48 weeks (about a year) on the 12 mg dose. 

Here’s a look at the latest research on retatrutide for weight loss:

• In a trial of people with obesity or overweight and a weight-related condition (e.g. prediabetes), those taking retatrutide lost 7%–17.5% of their body weight in six months. In a year, they lost 9%–24% of their body weight. Higher doses led to more weight loss; for example, people taking 8 mg and 12 mg weekly lost 23%–24% in a year. 

• In a study of individuals with nonalcoholic fatty liver disease, those taking 8 mg and 12 mg of retatrutide lost over 17% of their body weight in six months. After a year, they had lost 24%–26% of their body weight, along with up to 8 inches off their waistlines.

• In a study of people with obesity and knee osteoarthritis, participants taking 9 mg and 12 mg of retatrutide lost 26.4%–28.7% of their body weight in 68 weeks (about a year and four months). That translated to an average weight loss of 64–71 pounds.

Beyond weight loss, retatrutide may also offer additional health benefits. In the clinical trial of people with obesity and overweight: 

• Over 70% of people with prediabetes at the beginning of the study had achieved normal HbA1c levels within 48 weeks (~one year).

• Up to 40% of people taking high blood pressure medications at the beginning of the study had stopped taking at least one medication within 48 weeks (~one year).

Since retatrutide is still being studied and not yet approved by the US Food and Drug Administration (FDA), it currently doesn’t have an official dose or dosage. 

However, the following dosage strengths were studied in clinical trials for obesity, fatty liver disease, and osteoarthritis: 

• 1 mg

• 4 mg

• 8 mg

• 9 mg 

• 12 mg 

In these studies, retatrutide was taken weekly, similar to other GLP-1 medications like Ozempic, Wegovy, Zepbound, and Mounjaro. 

Common retatrutide side effects reported in clinical trials were gastrointestinal in nature — similar to those of approved GLP-1s:

• Nausea

• Diarrhea

• Vomiting 

• Constipation 

Retatrutide’s side effects are also similar to GLP-1s in that they tend to range from mild to moderate and are most common when starting the medication or increasing the dose. 

Other side effects that were reported more frequently on retatrutide vs. a placebo include:

• Decreased appetite

• Hypertension (high blood pressure)

• Abdominal pain

• Fatigue

• An increase in lipase levels, which can be a sign of pancreatitis

• Dizziness

• Upset stomach or indigestion

• Belching

• Upper respiratory tract infections

• Changes in touch, such as “pins and needles” or crawling sensations

Retatrutide is not yet on the market in the US, so the only way to get it is through a clinical trial — that is, if you’re eligible and approved. 

To find a clinical trial near you:

1. Visit ClinicalTrials.gov. 

2. Enter “retatrutide” in the “Intervention/treatment” box.

3. Select "Recruiting and not yet recruiting studies.” 

4. You can also enter your location if you wish. 

After you press the “Search” button, you’ll see a list of all the clinical trials that are looking for people to join them. You’ll also see where these studies are located, how long they’re expected to last, and any eligibility requirements (such as current medical conditions).

Be aware that there can be some downsides to participating in a clinical trial. With experimental drugs, researchers don’t yet know all the risks or side effects (that’s part of what they’re looking for in a clinical trial, after all). And it’s possible that you might be given a placebo instead of the drug being studied.

It’s possible retatrutide could be available sometime in 2026. However, it’s more likely it will be available in 2027. That’s because the phase 3 trials have to be completed before Eli Lilly can apply for FDA approval of the drug. 

Those trials are expected to finish in late spring 2026, and the FDA approval process can take 6–10 months. So, if Eli Lilly immediately applies for approval and the FDA fast-tracks it, the earliest we could expect an approval of retatrutide for weight loss would be November or December 2026.

Eli Lilly has not released any information on the cost of retatrutide. We won’t know the price of retatrutide until (and if) it's approved by the FDA, and Eli Lilly announces the official amount.

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Retatrutide is a new GLP-1-based drug currently being developed by Eli Lilly for weight loss and related conditions. Until (and if) it gets approved by the FDA, here’s what we know:

• Retatrutide is a GIP–GLP-1–GCG triple receptor agonist that works for weight loss by mimicking three hormones to slow digestion, boost metabolism, and suppress appetite.

• In clinical trials, retatrutide led to an average weight loss of up to 23%–29% in about one year. So, if approved, it could be the most effective weight loss injection available.

• Similar to approved GLP-1s, retatrutide is injected under the skin once weekly.

• Since it’s still being studied, there isn’t an official retatrutide dosage or cost yet; these will be announced if the drug gets approved. 

• The most common side effects of retatrutide are gastrointestinal, such as nausea, vomiting, and diarrhea.

• At this time, you can only get retatrutide through clinical trials; it is not available online or even on the market in the US.