Medically reviewed by Puja Vyas, Lead Clinical Pharmacist.

Wegovy and Mounjaro are both once-weekly injections licensed in the UK for weight management. Both are licensed by the MHRA.

The difference comes down to mechanism, results, and what your body actually needs.

Mounjaro works on two appetite-regulating hormones, GLP-1 and GIP, while Wegovy works only on GLP-1. The first-ever head-to-head clinical trial (SURMOUNT-5, NEJM May 2025) found Mounjaro produced 20.2% average weight loss versus 13.7% with Wegovy over 72 weeks. That’s roughly 47% more.  

What’s right for you? That depends on your weight loss goal, your health history, and for men specifically, what visceral fat (the fat surrounding internal organs) is doing to your testosterone, your heart, and your metabolic baseline. We'll cover all of this.

Note: Wegovy is now available in an oral pill form too. For this article we’ve stuck to comparing both injections. We’ve written another full article on Wegovy Pill for men.

What are Wegovy and Mounjaro?

What is Wegovy?

Wegovy contains an active ingredient called semaglutide, a GLP-1 receptor agonist developed by Novo Nordisk. GLP-1 (glucagon-like peptide-1) is a hormone that your gut releases after eating, signalling your brain to reduce hunger and increase fullness.

Semaglutide mimics this hormone in an amplified manner. Ozempic is a lower-dose version of the same. 

Wegovy is the higher-dose formulation (up to 2.4 mg, or the new 7.2 mg dose) licensed specifically for weight management. It's been available in the UK since 2023. 

For eligibility detail, read our Wegovy guide for men.

What is Mounjaro?

Mounjaro, developed by Eli Lilly, contains tirzepatide, a dual-action receptor agonist that works on GLP-1 and GIP appetite regulating hormones. GIP (glucose-dependent insulinotropic polypeptide) works alongside GLP-1 to enhance fat metabolism and energy processing. This additional mechanism is why Mounjaro tends to produce greater average weight loss. 

NICE recommended Mounjaro for use on the NHS in December 2024, but access remains limited.

For the full picture, see our Mounjaro for men guide.

Wegovy vs Mounjaro: comparison

Wegovy and Mounjaro at a glance (for information)
WegovyMounjaro
Active ingredientSemaglutideTirzepatide
How it worksGLP-1 receptor agonistGIP and GLP-1 receptor agonist
UK licence for weight managementYes (MHRA)Yes (MHRA)
NICE recommendation (NHS)TA875, March 2023TA1026, December 2024

Wegovy vs Mounjaro: what the weight loss trials show

What data shows

Before May 2025, a direct comparison was difficult as no study showed directly comparable results because of there being two different mechanisms and dosages. So, clinicians compared these drugs across separate trials with different patient populations. 

The SURMOUNT-5 trial: the first direct comparison

The head-to-head comparison got published in the New England Journal of Medicine on 12 May 2025. SURMOUNT-5 was the first phase 3b randomised controlled trial to compare tirzepatide and semaglutide in the same patients, at the same time, under the same conditions.

751 adults with obesity but without type 2 diabetes. Maximum tolerated dose of each drug. 72 weeks.

The result:

  • Tirzepatide (Mounjaro): 20.2% average weight loss
  • Semaglutide (Wegovy): 13.7% average weight loss
  • Tirzepatide participants more likely to reach every weight-loss threshold, ≥10%, ≥15%, ≥20%, and ≥25%
  • GI side effects were common in both groups but led to discontinuation in only 3% on tirzepatide and 6% on semaglutide

Side effects: Wegovy vs Mounjaro

The common ones

Because both act on GLP-1 receptors, the side effect profile is fundamentally similar. You can expect -

  • Nausea (most common, especially in the first weeks and around dose step-ups)
  • Constipation
  • Diarrhoea
  • Stomach discomfort, bloating, or reflux
  • Reduced appetite (obviously)

Side effects are usually mild to moderate and tend to improve as your body adjusts. The slow dose escalation on both medications helps manage them.

Sources: NICE Technology Appraisal TA1026 (tirzepatide) and TA875 (semaglutide); the MHRA product information for both medicines.

Where they differ

Some men experience more nausea on Mounjaro, probably because of its dual-hormone action. Constipation, on the other hand, appears slightly more common with semaglutide. Only 3% sample population with tirzepatide and 6% with semaglutide discontinued due to side effects as per the SURMOUNT-5 study. 

Neither medication causes hypoglycaemia on its own, though this becomes a risk when combined with insulin, sulphonylureas, or glinides. Both carry a small risk of pancreatitis and gallbladder issues. Neither is suitable for everyone: the clinician screens your medical history, and each medicine's patient information leaflet carries the full list.

Text infographic advising anyone on GLP-1 treatment to stop and seek urgent medical advice for severe abdominal pain spreading to the back, sudden vision changes or signs of an allergic reaction, and noting that HeMed clinicians provide support throughout the programme.
The warning signs that mean stop and seek urgent advice - and a reminder that clinical support is there throughout.

NHS and private access in the UK

Both are available privately in the UK. On the NHS, NICE recommends semaglutide (TA875, March 2023) within specialist weight management services and tirzepatide (TA1026, December 2024), each within its own eligibility criteria. NHS access is being phased in.

Private prices vary by provider and by dose. HeMed's plan prices are listed on the Wegovy and Mounjaro pages.

Wegovy vs Mounjaro: how the two differ

Wegovy: what sets it apart

Wegovy has a longer clinical track record in the UK and an additional cardiovascular benefit which can be a real difference for some men. The SELECT trial with 17,604 patients, published in the NEJM and analysed further in The Lancet in October 2025, showed that semaglutide reduced major adverse cardiovascular events (heart attack, stroke, cardiovascular death) by 20%. This benefit was irrespective of the weight loss.

This makes Wegovy a better option for -

  • Men with established cardiovascular disease or elevated CVD risk
  • Those who previously used Ozempic for diabetes and tolerated semaglutide well 
  • Those who find the dual action of Mounjaro a bit too much to tolerate
  • Those for whom monthly cost is a significant deciding factor.

Mounjaro: what sets it apart

Mounjaro is best for men for whom maximum weight loss is the first priority, particularly for ones with significant visceral fat, those whose body haven’t responded sufficiently to Wegovy or semaglutide, or those whose metabolic profile is more suited for Mounjaro’s dual-hormone action.

Wegovy vs Mounjaro for men specifically

Men carry proportionally more visceral fat (the fat surrounding internal organs) than women at equivalent BMI (body mass index, a measure of weight relative to height) levels. Visceral fat is one of the most contributing factors that drive cardiovascular risk, insulin resistance, low testosterone, and sleep apnoea.

Both medications reduce it. Mounjaro reduces it more.

One conference study (ENDO 2025) reported higher testosterone in men who lost 10% of body weight on these medicines; it is not yet peer-reviewed. The greater the weight loss, the stronger the hormonal recovery.

The elephant in the room: why men delay starting

Despite representing the majority of those classified as obese with high metabolic risk men make up only around 30% of NHS weight management referrals. We’ve seen some men associating injectable weight loss medication with giving up or not for them. That’s both, outdated and medically wrong. 

Obesity has a strong genetic and hormonal component. For men, where androgen levels influence fat distribution and metabolic rate, that’s more applicable. Wegovy and Mounjaro target the hormonal system that regulates appetite, making them a clinical intervention for a clinical problem, not a shortcut.

Other point that we often come across is that men tend to delay until health complications have already arrived. This includes high blood pressure flagged at a routine check, a GP mention of pre-diabetes, or a family history of heart disease starting to feel real.

Both medications reduce visceral fat directly. And earlier treatment means faster improvement in the markers that matter.

Can I switch between Wegovy and Mounjaro?

Switching from Wegovy to Mounjaro

Yes, but only under medical supervision. Men mostly think of switching only because of two reasons - 

  • Not hitting target weight loss on Wegovy, wanting to try the dual-mechanism approach
  • Or reaching a plateau in the weight loss journey. 

Because the two medications use different dosing scales and mechanisms, switching is not a direct swap. A clinician needs to review your current dose, progress, and health picture, to advise on timing and starting dose for Mounjaro.

Switching from Mounjaro to Wegovy

Again, it’s possible but should be done only under medical guidance. Here, the most common driver is cost. Prices for Mounjaro increased significantly in 2024 and this made many men think that Wegovy's weight-loss profile is sufficient for their goals at a lower monthly spend. 

Can you take both at the same time?

Strictly No. While both medications target GLP-1 receptors, taking them together provides no additional clinical benefit. It can increase the risk of side effects significantly. 

 

At HeMed, every programme starts with a mandatory at-home blood test and clinician review. We look at your metabolic markers, health history, and goals, then recommend the right medication, at the right dose, for you.

Frequently asked questions

Is Mounjaro better than Wegovy for weight loss?

In the first direct head-to-head trial (SURMOUNT-5, NEJM 2025), tirzepatide produced 20.2% average weight loss versus 13.7% with semaglutide over 72 weeks. Mounjaro's dual GIP and GLP-1 mechanism targets two appetite-regulating hormones rather than one. That said, both are highly effective, and the right choice depends on your health profile, history, and goals.

What are the side effects of Wegovy vs Mounjaro?

Side effects are similar with both medications. They include nausea, diarrhoea, constipation, and stomach discomfort, that are most common initially and around dose increases.

Mounjaro may cause slightly more nausea early on and Wegovy slightly more constipation. But SURMOUNT-5, discontinuation due to side effects was 3% on tirzepatide and 6% on semaglutide.

Is Wegovy or Mounjaro available on the NHS?

Wegovy is available via specialist weight management referral on the NHS. Mounjaro received NHS approval in December 2024 but access remains very limited. In England, prescribing is restricted to GP practices meeting specific criteria.

How do Wegovy and Mounjaro compare for men?

The head-to-head data favours Mounjaro for total weight loss, particularly visceral fat reduction which is important for men's metabolic and hormonal health. Wegovy's, on the other hand, has clinically proven cardiovascular benefits.

Neither is universally "the best". It depends on what you're optimising for.

Sources

HeMed is a clinician-led weight loss and metabolic health service for men in the UK, built around an at-home blood test. All clinicians are UK-registered. This article is for information only and does not constitute medical advice. Always consult a qualified clinician before starting or changing any treatment.