Retatrutide is a new drug that works similarly to Mounjaro and Wegovy. It’s still in clinical trials, so you can’t be prescribed it yet, but research on retatrutide as a treatment for type 2 diabetes and weight management is showing promising results.
Like all medications though, retatrutide does cause side effects for some people. Here’s what we know so far.
What is retatrutide and how does it work?
Retatrutide is a once-weekly weight loss injection that combines the actions of three key metabolic hormones:
- GLP-1 (helps you feel full and keeps blood sugar in balance)
- GIP (supports insulin release and helps your body process food for energy)
- Glucagon (tells your body to burn fat for energy)
This “triple G” mechanism sets it apart from Wegovy, which targets one hormone, and Mounjaro, which targets two. Retatrutide is the first triple-agonist medicine being developed for obesity and weight loss.
Clinical trials are showing greater weight loss results than any medication currently available. Participants taking the highest dose (12mg) lost just over 24% of their body weight in 48 weeks, and 26% of participants lost at least 30% of their initial weight.
In comparison, studies show that Mounjaro users lost 22.5% of their body weight on average after 72 weeks, and Wegovy users taking a 7.2mg dose lost up to 20.7% of their body weight after 72 weeks.
So if retatrutide is more effective than other GLP-1s, does it still have side effects, and are they the same ones?
Most common side effects of retatrutide
The most commonly reported side effects from retatrutide clinical research are digestive issues, including:
- Nausea
- Diarrhoea
- Vomiting
- Constipation
These are similar to Wegovy's side effects and those seen with Mounjaro.
At higher doses of retatrutide (8mg and 12mg), side effects became more common, but were still rated as mild to moderate.
Retatrutide heart effects
There is some evidence that retatrutide side effects can have a mild impact on heart rate and rhythm, but again, it’s dose-dependent.
Some participants taking higher doses of retatrutide in phase 2 clinical trials had a slightly higher resting heart rate. In the phase 2 trial, the largest average rise was about 6.7 beats per minute at 24 weeks on the highest 12 mg dose, with rates declining again by weeks 36 to 48. The rise in heart rate appeared dose-dependent and was similar to changes seen with GLP-1 medicines.
A small number of people also had mild changes in heart rhythm (arrhythmias). Despite this, no increase in heart attacks or serious heart problems has been reported so far.
Retatrutide also showed potential cardiovascular benefits. Participants saw improvements in blood pressure, blood sugar, insulin and cholesterol levels, with many reverting from prediabetes to normal blood sugar levels. Around 4 in 10 participants were able to stop at least one blood pressure medicine during treatment.
The long-term effects of retatrutide on heart health are still unknown, but a clinical trial is underway to see if it could be beneficial for heart-related complications and kidney function.
Side effects support at Voy
"If you're using Voy and you experience any side effects, rest assured that our expert clinicians are just a message or phone call away. They can adjust your dose, prescribe medication to ease your symptoms, or simply offer reassurance.
Everyone responds differently to weight loss treatment and we'll help you find what feels right for you."
Can retatrutide cause hair loss?
Currently, there is no evidence to suggest that retatrutide directly causes hair loss. The studies on retatrutide so far have been relatively short, so we’re still learning about potential side effects.
From research on other GLP-1s, we know that 3% of Wegovy users and up to 5.7% of Mounjaro users reported some hair loss—but it’s usually temporary.
Temporary hair loss (telogen effluvium) while taking GLP-1s is more likely caused by losing weight quickly, rather than the medication itself. Your body might have a stress response, and pause hair growth. If you do lose hair, make sure you’re getting the nutrients you need to support a healthy metabolism.
Retatrutide skin effects
A small proportion of study participants reported skin side effects with retatrutide (7%). This included symptoms like skin sensitivity, tenderness, pain when touched, tingling, and sensitivity to pressure or heat.
However, these side effects were mild and didn’t cause anyone to stop treatment.
Can retatrutide affect your sleep?
So far, no clinical studies have shown that retatrutide impacts sleep.
Sleep-related side effects on retatrutide could be linked to consuming fewer calories as you lose weight. When you eat less, energy gets used up quickly, and you can feel fatigued sooner.
On the flip side, there’s some evidence to show that GLP-1 medications may make you less sleepy. A meta-analysis looked at obese participants with obstructive sleep apnea (OSA) and found they had fewer breathing interruptions at night as they lost weight.
Retatrutide long-term side effects
Because retatrutide is still in the trial phase, and the studies have been relatively short (up to a year long), we don’t know what the long-term side effects will be.
The majority of participants reported mild to moderate side effects that were not long-term. The current evidence points to retatrutide being safe overall, but monitoring by a healthcare provider during treatment is still important.
Serious side effects were rare, occurring in about 4% of participants in both the retatrutide and the placebo group, so this risk wasn’t higher because of retatrutide.
How long do retatrutide side effects last?
Retatrutide side effects are generally worse early on then improve as treatment continues.
The gastrointestinal side effects were more likely to be present when the dose was being increased. Over time, these side effects decreased or became milder as participants adjusted to a stable dose.
Who should not use retatrutide?
As retatrutide isn’t approved yet, we can’t say for sure. Based on the restrictions for Wegovy and Mounjaro, retatrutide may not be suitable for you if you:
- Are pregnant or breastfeeding
- Have a history of gallbladder, kidney, or pancreas problems
- Are under 18
- Have a family history of certain types of thyroid cancer
- Take certain medications
Where can I buy retatrutide?
Retatrutide is still in clinical trials and isn’t available for general use yet, so be cautious of anyone claiming to sell it already. If approved, it’ll likely become available in late 2026.
Always consult a healthcare provider before taking any new medication, and get GLP-1s from a trusted, reliable source.
If you want to start your weight loss journey now, Voy offers alternatives to retatrutide like Wegovy (semaglutide) and Mounjaro (tirzepatide) in our science-backed weight loss programmes. These treatments have been proven to show seriously effective results. Take our quiz today to help you find your perfect plan.
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