Is Retatrutide Safe?

Retatrutide looks promising so far, but it is not yet proven safe for general use in the way an approved medicine is. It is still being tested in clinical trials, where researchers assess the right dose, how well it works, and whether the benefits of treatment outweigh the risks.

Before any medicine can be sold in the UK, the manufacturer must submit a full data profile of the drug, detailing its safety, quality and effectiveness to the MHRA. Eli Lilly is still carrying out this process for retatrutide.

The encouraging news is that, so far, no major unexpected safety concerns have emerged from the available trial data. The side effects of retatrutide reported to date, appear broadly similar to other weight, such as nausea, diarrhoea and vomiting, especially during dose increases.

However, retatrutide is not approved in the UK, so it is not safe to buy online from unofficial sources. Products sold this way may be fake, contaminated, incorrectly dosed or improperly stored, meaning you cannot be sure what you are getting.

In clinical trials, the reported side effects of retatrutide are similar to other weight loss injections. These include nausea, diarrhoea, vomiting, constipation and reduced appetite.

These are usually worst when the dose is being increased and are often mild to moderate rather than dangerous.

Further reading: Retatrutide side effects

The more serious side effects people worry about are broadly similar to those discussed with other GLP treatments. These include:

• Pancreatitis
• Gallbladder problems such as gallstones or gallbladder inflammation
• Severe dehydration from prolonged vomiting or diarrhoea
• Allergic reactions
• Possible issues around delayed stomach emptying, including an increased aspiration risk around anaesthesia or deep sedation with this class of medicines

These side effects are rare, however, they are a possibility and it is important to be aware of them.

In the phase 2 diabetes trial, 16 of 190 retatrutide-treated participants (8%) stopped treatment because of side effects overall.

Serious adverse events were reported in 11 of 190 participants (6%).

The serious adverse events appear to be related to retatrutide. They were cholecystitis, acute pancreatitis, and diabetic plus starvation ketoacidosis. The trial also recorded one major adverse cardiovascular event.

In the phase 3 diabetes trial, 537 participants were randomised in total.

So far, Lilly has only released overall discontinuation rates due to side effects.

The discontinuation rates were 2.2% with retatrutide 4mg, 4.5% with 9mg, and 5.1% with 12mg, compared with 0% on placebo.

The most common adverse effects were nausea, diarrhoea, vomiting, and dysesthesia, mainly during dose escalation.

Lilly has not yet publicly reported the overall serious adverse event rate, how many people stopped specifically because of serious adverse events, or what they were.

Across the clinical trials so far, the main concern appears to be tolerability rather than a clear major new safety problem, but the full safety picture is still being defined.

Because retatrutide is not yet licensed, there is no final approved UK contraindications list.

However, based on how similar medicines are prescribed, there are several groups where we can expect treatment to be contraindicated, or used with caution.

Pregnancy

These type weight loss medicines should not be used during pregnancy, and the MHRA advises contraception and washout periods for licensed medicines in this class. This is because there is not enough safety data in pregnancy. Retatrutide would be expected to follow the same cautious approach unless future data showed otherwise.

Breastfeeding

Retatrutide is unlikely to be licensed for those that are breastfeeding. It is highly unlikely that trials will include those that are breastfeeding, so there will not be enough evidence to know whether they could affect the baby.

Personal or family history of certain thyroid cancers

Mounjaro should not be used in people with a personal or family history of medullary thyroid cancer, or MEN2. This is because it caused thyroid C-cell tumours in animal studies. It is not known whether this risk applies to humans, but the warning is kept in place as a safety precaution.

There is a strong possibility that this warning may also apply to retatrutide, given that it is similar in nature.

History of pancreatitis

Anyone with a history of pancreatitis would need careful assessment. The MHRA has strengthened warnings for GLP-1 and GLP-1/GIP medicines about acute pancreatitis, including rare severe cases, so this is a group where extra caution would be expected.

Gallbladder disease

Weight loss injections need extra caution in people with a history of gallbladder disease because they can increase the risk of gallstones and gallbladder inflammation. This is partly linked to rapid weight loss itself, and partly because these medicines may slow gallbladder emptying.

Severe stomach or gut emptying problems

Because this class slows stomach emptying, people with severe gastrointestinal disease, especially severe gastroparesis, may not tolerate it well and may be at higher risk of complications.

People due to have surgery or sedation

The MHRA has warned about a possible aspiration risk with GLP-1 and GLP-1/GIP medicines during general anaesthesia or deep sedation because of delayed stomach emptying.

Retatrutide would likely need the same type of peri-operative caution if approved.

At the moment, the safest way to use retatrutide is through an official clinical trial.

Until it receives regulatory approval, it should not be bought from social media sellers, Telegram channels or random websites.

If retatrutide is eventually licensed, the safest way to obtain treatment would be through a registered pharmacy or clinic.

Further reading: Where to buy retatrutide

This ensures that there is a genuine clinical need, the treatment is appropriately prescribed and proper monitoring is conducted.

In the UK, licensed GLP-1 medicines are prescription-only treatments intended for specific medical indications, not casual cosmetic weight loss.

Mounjaro

Mounjaro (tirzepatide) is a licensed option in the UK. It acts on GIP and GLP-1, so it is somewhat similar to retatrutide but without the glucagon pathway. It has already been assessed by regulators and has established product information, prescribing rules and safety monitoring.

Further reading: Retatrutide vs Mounjaro

Wegovy

Wegovy (semaglutide) is another licensed UK option. It works through GLP-1 only. Although it is not as effective as retatrutide, it has a defined evidence base, established warnings and regulated supply.

Orforglipron

Orforglipron is still undergoing clinical trials, but it is one of the most interesting pipeline alternatives because it is an oral GLP-1 tablet, not an injection.

In Lilly’s phase 3 obesity data, the highest dose produced average weight loss of 12.4% at 72 weeks, and around 39.6% of participants on the highest dose lost at least 15% of their body weight.

Lilly says its safety profile has been consistent with the injectable GLP-1 class.

Wegovy pills / oral semaglutide

Oral Wegovy tablets are also being studied as a future oral alternative. In clinical trials, oral semaglutide 25mg produced an average body weight reduction of 13.6% at 64 weeks versus 2.2% with placebo.

Gastrointestinal side effects were more common than placebo, and discontinuation due to adverse events was 7% versus 6% with placebo.

Retatrutide looks very promising from a safety and effectiveness point of view so far. It appears to work in a similar way to popular medicines like Mounjaro, but with an extra glucagon pathway that may help explain the even stronger weight-loss results seen in trials.

The main issues reported to date have largely been the stomach side effects rather than a clearly unexpected major safety signal.

But promising is not the same as approved. Retatrutide is still in clinical trials, and the full safety picture is still being built. In the UK, you will need to wait for a regulator such as the MHRA to assess the evidence and approve it before it can be supplied lawfully as a medicine.

Until then, it is not safe to buy retatrutide online, because products sold outside authorised trials may be illegal, fake or dangerous.