Mounjaro vs Wegovy: Which Is Right for You?
This is what most of our initial consultations look like: “I’ve done the research, I know I want to start a weight loss injection, but I cannot figure out whether Mounjaro or Wegovy is the one for me.”
This is a very valid concern for someone starting their transformation journey.
Both are weekly injections. Both are licensed in the UK. Both work. But we know that the information on the internet and social media can feel overwhelming. So we’ve tried to cut the noise and give you a clear picture here.
In May 2025, both medications were tested against each other in the same trial for the very first time; same patients, same conditions, same time period. And it has answered many questions.
Let’s start with the fundamental questions.
What Are Mounjaro and Wegovy?
How Wegovy Works
Your body has a hormone called GLP-1. It is the messenger that signals your brain when you’re full so you stop eating.
The problem is, for a lot of women, that messenger doesn't shout loud enough. So the brain never gets the message on time. So your brain keeps thinking about food even when you’ve just had a full meal (with dessert).
Here’s where Wegovy comes in.
Wegovy contains semaglutide, an active ingredient that acts exactly like that messenger, but louder and longer. It slows down how quickly food leaves your stomach, and helps keep your blood sugar steady.
The result? You feel full sooner and for longer. So that feeling when you can’t stop thinking about food, goes away. That's it. No magic. Just your own biology, working the way it was supposed to.
Wegovy comes as a once-weekly injection and is available in the UK at doses starting from 0.25mg, working up to 2.4mg. In January 2026, a higher dose of 7.2mg was approved by the MHRA for those who need additional support.
How Mounjaro (Tirzepatide) Works
Remember the little messenger we talked about with Wegovy?
Mounjaro does the same thing, but it sends two messengers instead of one.
The first one is GLP-1, the same as Wegovy. The second is called GIP. Its job is to help your body handle sugar better and tell your body more firmly that ‘time to leave the plate.’
Together, these two messengers don't just turn the volume down on hunger, they also help your body use energy more efficiently. This dual action system is why, on average, people tend to lose more weight with Mounjaro than Wegovy.
Best way to think about it: Wegovy turns down the volume on your hunger. Mounjaro turns down the volume and unplugs the speaker.
It comes as a once-weekly injection, starting at 2.5mg and going up to 15mg depending on what your body needs.
Key Differences: Efficacy and Dosage
*SURMOUNT-5 head-to-head trial, NEJM 2025. Intention-to-treat population. Both groups without type 2 diabetes. Eli Lilly funded.
Weight Loss Results: What Does the Clinical Evidence Say?
Earlier, a direct comparison was difficult as we had to compare the two drugs using separate trials with different patient populations. SURMOUNT-5 changed that.
In the trial, 751 adults with obesity or overweight plus at least one weight-related condition were randomly assigned to either Mounjaro or Wegovy for 72 weeks. Results:
- Mounjaro: 20.2% average weight loss
- Wegovy: 13.7% average weight loss
- Waist circumference reduction: 18.4cm (Mounjaro) vs 13.0cm (Wegovy)
- Achieving 20%+ weight loss: 1 in 3 Mounjaro patients vs significantly fewer on Wegovy
That’s about 47% more weight loss on average with Mounjaro. But before you start forming opinions about Wegovy, its 13.7% is still extraordinary by any historical standard. Before it, no non-surgical intervention came close to these results.
And the most important thing to know here is that these are averages from a sample population. Individual response varies enormously. For some women the weight loss on Wegovy is much higher than what it would be on Mounjaro.
So, chasing the average is not the right way to assess the success of any drug. And nor is just the figure on the weighing scale. You’ll know why soon. Keep reading.
Dosage Schedules and Dose Equivalents
Both are different molecules measured in different units. Hence, they cannot be compared directly.
- Mounjaro: Starts at 2.5mg, titrates through 5mg, 7.5mg, 10mg, 12.5mg to a maximum of 15mg
- Wegovy: Starts at 0.25mg, titrates through 0.5mg, 1mg, 1.7mg to 2.4mg (and now 7.2mg for those who need it)
Its ‘start low, go slow’ and titrate up over approximately 16–20 weeks for both. And this is not because the makers of the drugs want to avoid court cases. Starting at a lower dose significantly reduces the risk of nausea and GI side effects during the adjustment period.
The whole point will be lost if the initial side effects make you stop your journey. Talking about which -
Side Effects: Mounjaro vs Wegovy
As we said earlier, most of the side effects are common in both, with some differences.
Common side effects
- Nausea (the most common one across both)
- Constipation
- Diarrhoea
- Fatigue (in early weeks)
- Vomiting (Commonly during dose increases)
Most are gastrointestinal, mild to moderate, and improve significantly after the dose escalation phase.
The different ones
- GI discontinuation rate: 5.6% of semaglutide (Wegovy) users stopped due to GI side effects, vs 2.7% of Tirzepatide (Mounjaro) users
- Diarrhoea: Common with Mounjaro because of its dual action
- Nausea and constipation: Seen more in Wegovy
- MHRA NAION warning (February 2026): Both medications carry an updated warning about a very rare but serious eye condition (non-arteritic anterior ischaemic optic neuropathy).
Individual tolerance varies significantly. Some women sail through Mounjaro’s titration with barely a second thought; others find Wegovy more manageable. There’s no way to predict this in advance, which is why clinical monitoring during the adjustment period matters.
Cost and Availability in the UK
Private Costs: Wegovy vs Mounjaro
Both medications are available privately in the UK. Here’s the honest picture in 2026:
- Wegovy injection: £130–£150/month at starter doses · £200–£295/month at 2.4mg · £295+/month at 7.2mg
- Mounjaro: From £149/month at 2.5mg, rising to £300–£375/month at the 12.5mg–15mg maintenance doses (after September 2025 price increases)
The prices for the starting doses are somewhat similar. At maintenance doses, though, Mounjaro has become significantly more expensive after the 170% price increase in September 2025.
So, if budget is a key factor, Wegovy currently offers better value per pound spent, especially with the 7.2mg dose now available.
NHS Access and Eligibility
NHS access for both medications is currently limited, but things are changing:
- Weight management (Specialist services): Both Mounjaro and Wegovy are available through NHS specialist weight management services. Eligibility typically requires BMI 35+ with at least one comorbidity. The waiting lists, however, are around 6-18 weeks in many areas.
- GP prescribing (Mounjaro, rolling out 2026–27): Mounjaro prescription through GPS is being expanded via integrated care boards. You may see it happen in 2026-27. The BMI eligibility criteria may also widen over the coming years.
- New CV indication for Wegovy (NICE, April 2026): Adults with cardiovascular diseases like previous heart attack, stroke, or peripheral arterial disease, etc. and a BMI of 27+ can be prescribed Wegovy by the NHS. NHS trusts must make it available within 90 days of final guidance (expected from late summer 2026).
In April 2026, NICE officially approved Wegovy as a heart medicine as well. Around 1.2 million people in England qualify for Wegovy because of this. NHS trusts are expected to make it available from late summer 2026.
Which Is Right for You? Mounjaro vs Wegovy for Women
Honestly, neither we nor this article can make this decision for you and it shouldn't. Our job is to make sure that you know the right questions to ask your clinician and then make an informed choice. Here’s what we think how you should approach it -
Wegovy may suit you if…
- You're new to weight loss medications and want to start with a well-established, extensively studied option. Wegovy has been available for longer, and hence, has more long-term real-world data behind it.
- You want to start with a gentler option (single mechanism), as compared to Mounjaro’s dual action system.
- You found Mounjaro's side effects harder to manage.
- You want to keep your options open for the oral pill version (launched in the US), expected to be launched soon in the UK after MHRA review.This is particularly for people with a needle phobia. Read the full article on it. (add link to our pill article)
You May Suit Mounjaro If…
- Your weight loss journey with Wegovy has plateaued (most common reason for women to switch). Mounjaro restarts progress that semaglutide alone couldn't sustain.
- Maximising results is your primary goal and your health profile supports it.
- You have type 2 diabetes or significant insulin resistance as Mounjaro was originally developed as a diabetes medication and has shown a strong evidence base for blood sugar control alongside weight loss.
- You couldn’t handle the nausea or constipation on Wegovy. Data showed more Wegovy users stopping treatment because of them than Mounjaro users.
Special Considerations: PCOS, Perimenopause, and Hormones
Weight loss on GLP-1 medications can have meaningful effects on hormonal health too. And this is where we feel these medications deserve more credit than they receive.
.
PCOS:
Weight loss itself, irrespective of medication, can significantly improve insulin sensitivity, reduce androgen levels, restore cycle regularity, and improve fertility outcomes.
Neither Mounjaro nor Wegovy is specifically licensed for PCOS in the UK. But women with PCOS who meet the BMI eligibility criteria (BMI 27+ with a metabolic comorbidity, or BMI 30+) can access both through private prescription.
Perimenopause and menopause:
We have all known about the weight gain in the perimenopause stage. The thing is it is not the one that disappears with exercise and diet alone. It is hormonal.
Here’s where these medications help. Both work on biology rather than just the behaviour, which is why many perimenopausal women respond particularly well.
Thyroid conditions:
If you’re taking levothyroxine, have active thyroid disease, or have a family history of medullary thyroid cancer, it is important to know that both medications carry a theoretical risk warning around thyroid tumours (based on rodent data, not confirmed in humans). Anyone with a history of MEN2 syndrome or medullary thyroid carcinoma should raise this with their prescriber.
Still not sure which one is right for you?
Frequently Asked Questions
Is Mounjaro stronger than Wegovy?
In the head-to-head SURMOUNT-5 trial (NEJM, 2025), Mounjaro produced 20.2% average weight loss vs 13.7% for Wegovy over 72 weeks. However, individual responses vary widely, and some women respond better to semaglutide than tirzepatide. Wegovy’s new 7.2mg dose (UK-approved January 2026) also narrows the gap, producing 20.7% average weight loss in its own trial.
Can I switch between the two?
Yes, you can switch between Mounjaro and Wegovy and it is very common. However, you cannot simply swap one for another. You’d need a new clinical assessment and a managed starting dose.
Do I need a prescription in the UK?
Yes. Both Mounjaro and Wegovy are prescription-only medicines in the UK. You cannot and should not buy them over the counter or legally obtain them without a valid prescription from a UK-registered prescriber. Any online seller offering either medication without a prescription is operating illegally and such drugs can be very harmful for you. Always verify GPhC registration at pharmacyregulation.org before purchasing.
Sources & Further Reading
2. NICE — Semaglutide Injection to Help Prevent Heart Attacks and Strokes (April 2026)
3. NHS England — Over a Million People Offered Wegovy for Cardiovascular Risk (April 2026)
4. NICE TA1026 — Tirzepatide (Mounjaro) for Managing Overweight and Obesity
5. NICE TA875 — Semaglutide (Wegovy) for Weight Management
6. SURMOUNT-1 Trial — Tirzepatide Once Weekly for the Treatment of Obesity (NEJM, 2022)
7. SELECT Trial — Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (NEJM, 2023)
8. MHRA — GLP-1 Medicines for Weight Loss and Diabetes (GOV.UK, 2026)
9. MHRA — Updated Semaglutide Guidance (GOV.UK, February 2026)
10. NHS — Obesity Treatment Overview
🔗 Source: Aronne LJ et al. — SURMOUNT-5: Tirzepatide vs Semaglutide for Obesity. NEJM, July 2025
🔗 Source: SURMOUNT-5 — NEJM 2025 (safety data)
🔗 Source: MHRA — Updated semaglutide guidance (GOV.UK, February 2026)
The content on the SheMed blog is provided for general informational and educational purposes only. While SheMed provides professional weight loss services and strives to ensure the information shared is accurate and up to date, we make no representations or guarantees as to its accuracy, completeness, or timeliness. This content should not be taken as personal medical advice or a substitute for consultation with a qualified healthcare provider. Always speak with your doctor or licensed medical professional about your individual health or medical needs before starting any new treatment or programme. Never disregard or delay seeking professional medical advice because of something you have read on this site. SheMed is not responsible for any actions you may take based on the information provided in this blog.
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