Scientists discover over 100 self-reported side effects linked to unapproved 'Godzilla' weight loss drug Reta

People have reported a series of positive and negative side effects after taking Retatrutide, apparently affecting everything from their mood and heart rate to their alcohol use and dreams, a new study has found.

Retatrutide, also known as 'Reta' and 'Godzilla', is an investigational, once-weekly injectable peptide developed by Eli Lilly.

Early trials have indicated that the weight loss drug could have huge benefits when it comes to people shedding some pounds, with one study finding that it could reduce a person's body weight by 25 percent.

What makes it different to medications like Wegovy and Ozempic is that Reta is a triple threat, as it mimics the hormones GLP-1, GIP, and glucagon. These help control appetite, blood sugar and metabolism.

With early trials signalling some positive results, people have been trying to get their hands on Reta for some time. It's yet to be approved by any regulatory body globally, however.

Despite this, people have still been able to access the drug through illegal 'gray markets'.

Retatrutide is yet to be approved for humans to use (Getty Stock Image)

New study looking into Reta

Those who have taken Reta via this market have gone on to share some of their side effects on social media platforms like Reddit. A new study, published in the journal JAMA Network Open on October 14, saw researchers examine 148,640 social media posts related to Reta on Reddit.

The posts came from 38,936 users across 27 retatrutide, peptide, and weight management communities from May 2021 to December 2025, the study said. They then whittled this down to 45,592 posts and comments from 13,589 unique users reporting Reta usage between the aforementioned dates.

Of this figure, nearly 8,000 people said they had experienced at least one side effect.

In total, there were 129 different side effects discussed online. Some were positive, while others were negative.

Eli Lilly is the manufacturer of retatrutide, AKA 'Godzilla' (Getty Stock Image)

Self-reported side effects of Reta

Of those who had reported side effects, 43.4 percent had experienced 'general disorders and administration site conditions' like fatigue, increased energy, and inflammation, while 33 percent had metabolism and nutrition disorders such as increased appetite and dehydration.

32.5 percent spoke about have having gastrointestinal problems like nausea and constipation, and a further 30.3 percent found it impacted them psychologically too. Insomnia was the highest reported psychiatric disorder (6.1 percent), and 3.8 percent had anxiety while taking Reta.

Other symptoms included dizziness, decreased blood pressure, back pain, lethargy, skin sensitivity, and blurry vision.

Both increased and decreased libido were reported, with 64 additional people saying their sex drive had decreased.

Others reported abnormal dreams (one percent), alcoholism (0.8 percent) and waking up multiple times in the night to pee (0.7 percent).

11.6 percent of Reta users reported that they'd experienced nausea (Getty Stock Image)

The most common symptoms were increased appetite (17.1 percent), fatigue (15.2 percent), increased energy (12.4 percent), nausea (11.6 percent) and food cravings (7.3 percent).

You can see the full list here.

The researchers noted that the symptoms could be 'misattribution rather than causal drug effects', also noting: "Product identity, purity, dose, route, treatment duration, concomitant medications, and medical history cannot be verified."

They also said that adverse side effects were likely to be reported at a higher rate on social media than as a percentage of clinical trial participants.

Eli Lilly's response

A spokesperson for Eli Lilly told UNILAD: "Retatrutide is an investigational molecule that has not been approved by any regulator anywhere in the world.

"Regulators around the world, including MHRA, have warned patients about the dangers associated with unapproved drugs, including black-market retatrutide.

"Anyone purporting to sell retatrutide to consumers is breaking the law. We have referred hundreds of black-market retatrutide sellers to regulators and law enforcement and call on them, as well as the companies whose services enable black market sales, to take decisive action to fight this urgent threat to public health.

"Lilly will continue to take action against those who break the law and endanger the public."