Medication Comparisons

Wegovy vs Retatrutide

Compare Wegovy and Retatrutide, including how they work, expected results, pricing expectations, and whether it makes sense to wait.

Whether you are weighing up Wegovy as your weight-loss treatment now, or watching retatrutide's development with interest, this guide compares them — what we know about each, where the comparison is meaningful, and where it isn't. The honest framing first: this is a comparison between a licensed UK medicine with extensive evidence (Wegovy) and an investigational medicine in phase 3 trials with no UK licence (retatrutide). They are not yet competing options. LetsLoseWeight is an independent comparison site; we do not prescribe medication.

Important: Retatrutide is not licensed by the MHRA and is not available from any regulated UK pharmacy. The comparison below is informational, drawing on Wegovy's full UK licence and clinical trial record alongside retatrutide's published phase 2 data. Anyone offering retatrutide for sale in the UK outside a registered clinical trial is doing so unlawfully.

At-a-glance comparison

Wegovy (semaglutide 2.4mg) Retatrutide
UK status Licensed by MHRA (2021) Not licensed
Available in UK Yes, from regulated pharmacies No (clinical trial only)
Pivotal trial weight loss ~14.9% at 68 weeks (STEP 1) ~24.2% at 48 weeks (phase 2)
Receptors targeted GLP-1 only GIP, GLP-1, glucagon
Trial size for weight management ~1,961 (STEP 1) plus thousands more across STEP programme ~338 in phase 2 obesity trial
Real-world data Years of post-marketing surveillance None
Cardiovascular outcomes data SELECT trial — 20% reduction in major events Not yet established
Typical UK private price £130–£300 per month No legitimate UK price
NHS access Yes (TA875, capped at 2 years) None

What's known about Wegovy

Wegovy is Novo Nordisk's brand for semaglutide 2.4mg, licensed in the UK for adults with overweight or obesity. The pivotal STEP 1 trial showed an average 14.9% weight loss at 68 weeks in participants without type 2 diabetes (Wilding et al., NEJM 2021).

Beyond the headline weight-loss figure:

  • The SELECT trial showed a 20% reduction in major cardiovascular events in adults with established cardiovascular disease and overweight/obesity (Lincoff et al., NEJM 2023)
  • Side-effect profile is well-characterised: gastrointestinal symptoms dominate, with headache, gallstones and other effects also known
  • Long-term safety data from semaglutide use in diabetes since 2017 supports the medicine's broader safety profile

For more, see our Wegovy results guide and Wegovy side effects guide.

What's known about retatrutide

Retatrutide is an investigational triple agonist developed by Eli Lilly. It activates three hormone receptors: GIP, GLP-1, and glucagon. The first two are also targeted by Mounjaro (tirzepatide); the addition of glucagon is what makes retatrutide novel.

The published phase 2 obesity trial showed average weight loss of around 24.2% at 48 weeks on the 12mg dose (Jastreboff et al., NEJM 2023). This is a striking result — larger than the headline figures from Wegovy and Mounjaro pivotal trials.

But the caveats matter:

  • Phase 2 trials are smaller (~338 participants) than phase 3 (typically thousands)
  • Phase 2 trials are shorter — 48 weeks vs Wegovy's 68 weeks
  • Phase 3 results sometimes differ from phase 2 in larger, more diverse populations
  • No head-to-head comparison with Wegovy or Mounjaro has been published

For more, see our retatrutide results guide and retatrutide side effects guide.

Why direct cross-trial comparison is tricky

Comparing 14.9% (Wegovy 68 weeks) with 24.2% (retatrutide 48 weeks) seems straightforward, but several factors make the comparison less clear-cut than the numbers suggest:

Different trial populations

The two trials enrolled similar but not identical participants. Differences in age, BMI, comorbidities, and other factors can shift outcomes meaningfully.

Different durations

Wegovy's 68-week trial includes the full titration plus extended maintenance. Retatrutide's 48-week trial captures peak weight-loss curve but ends before the typical late-stage slowing. A 72-week retatrutide trial might show somewhat different numbers.

Different doses studied

Wegovy's 14.9% is at the licensed maintenance dose (2.4mg). Retatrutide's 24.2% is at 12mg — a dose that has not yet been confirmed as the optimal phase 3 maintenance dose.

Phase 2 vs phase 3

The medicines are at very different stages of evidence. Phase 3 trials sometimes confirm phase 2 findings, sometimes refine them, and occasionally show smaller effects than phase 2 suggested.

A more honest summary: retatrutide phase 2 data is promising but provisional. Direct comparison with the established Wegovy evidence base will be more reliable when phase 3 data is available.

What the mechanism difference might mean

Wegovy targets only the GLP-1 receptor. Retatrutide targets three: GIP, GLP-1, and glucagon. This is hypothesised to give retatrutide:

  • Greater appetite suppression through combined GLP-1 and GIP activity (similar to Mounjaro)
  • Increased resting energy expenditure through glucagon activity
  • Greater fat breakdown in liver tissue, hence the related study programmes for fatty liver disease

But mechanism does not always translate cleanly to outcomes:

  • Side-effect profile may differ. Glucagon agonism could affect heart rate and arrhythmia risk — a signal flagged in the phase 2 trial that phase 3 will examine.
  • Tolerability is unknown for some patient subgroups (older adults, those with cardiovascular disease).
  • Long-term safety has not been characterised.

For comparison, see our Mounjaro vs Wegovy UK guide, where the dual-agonist Mounjaro (without retatrutide's glucagon component) is already showing greater average weight loss than Wegovy in the head-to-head SURMOUNT-5 trial.

Practical implications now

The practical answer to "Wegovy or retatrutide?" right now is:

  • Wegovy is available, evidence-rich, and a reasonable choice for many patients
  • Retatrutide is not available legitimately in the UK at this time
  • Mounjaro is also available and shows greater average weight loss than Wegovy in head-to-head data — and is therefore a more relevant comparison if you want greater results within the licensed-and-available set

Choosing between Wegovy and Mounjaro is a real clinical decision. Choosing between Wegovy and retatrutide isn't really a decision — it's choosing between something you can have and something you can't.

For the live decision, see our Mounjaro vs Wegovy UK guide and best weight loss injection UK decision framework.

When this comparison will become meaningful

If retatrutide receives MHRA marketing authorisation:

  • This page will be updated with the licensed schedule, side-effect profile, and price
  • A real Wegovy-vs-retatrutide decision will become possible for UK patients
  • NICE will assess retatrutide separately for NHS access criteria
  • Head-to-head trial data, if it emerges, will give a more reliable comparison than the current cross-trial comparison

There is no published timeline. Until retatrutide is licensed, this comparison is informational rather than decisional.

What about waiting for retatrutide?

A common question: "should I wait for retatrutide rather than starting Wegovy now?"

The honest answer is: probably not. Specifically:

  • There is no published date for retatrutide approval in the UK
  • The wait could be measured in years
  • Wegovy and Mounjaro produce real, clinically meaningful weight loss for the majority of patients
  • Untreated obesity continues to cause harm during the wait
  • You can switch to retatrutide later if and when it becomes available, restarting at its starter dose

The decision worth making is "which available treatment, now?", not "should I wait for the future treatment?"

Frequently asked questions

Will retatrutide really produce 24% weight loss when licensed?
Possibly, but not certainly. Phase 3 trials sometimes show smaller average effects. The 24% figure is the phase 2 average at 12mg; the eventual licensed maintenance dose, the licensed schedule, and real-world results may all differ.

Should I switch from Wegovy to retatrutide when it's licensed?
That decision will be available when retatrutide is licensed. At that point the comparison becomes a real clinical decision based on actual data, your individual response to Wegovy, side-effect tolerance, cost, and prescriber recommendation.

Is retatrutide more dangerous than Wegovy?
Unknown. Phase 2 data flagged some signals (heart rate, possible arrhythmias at higher doses) that phase 3 trials will examine. The current evidence does not support strong claims either way about long-term safety relative to Wegovy.

Why does retatrutide produce more weight loss than Wegovy?
The hypothesised mechanism is the addition of GIP and glucagon receptor activity to GLP-1. Whether the phase 2 effect size will hold up in phase 3 trials remains to be confirmed.

Can I get both Wegovy and retatrutide simultaneously?
No. Combining medicines that act on overlapping receptors risks severe side effects. There is no legitimate clinical scenario for combining them.

Next steps

Sources

This guide is for general information only. Retatrutide is not currently approved or available in the UK outside clinical trials.

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Wegovy vs Retatrutide UK: Cross-Trial Comparison | LetsLoseWeight