What are Mounjaro and Ozempic?
Mounjaro and Ozempic are both weekly injectable medications that mimic hormones our body produces after eating. They share some similarities but have important differences in what they’re approved to treat.
Mounjaro, made by Eli Lilly, contains the drug tirzepatide. It received UK approval for type 2 diabetes in 2023 and for weight management in late 2024, following NICE guidance (TA1026).2
Ozempic, made by Novo Nordisk, contains semaglutide. It’s approved in the UK for type 2 diabetes only.
Semaglutide is also available at higher doses under the brand name Wegovy, which is licensed for weight management. This is a common source of confusion.
Ozempic uses lower doses of semaglutide (up to 2 mg) than Wegovy (up to 7.2 mg).
Comparing Mounjaro to Ozempic at their respective licensed doses gives a different picture than comparing Mounjaro to Wegovy.
How these medications work
Both medications mimic hormones that are released by our gut to regulate hunger and blood sugar, but they work in different ways.
How Ozempic works
Ozempic mimics one hormone called GLP-1 (glucagon-like peptide-1), which has three main effects:
- Slows food movement through your stomach, helping you feel fuller for longer
- Communicates with your brain’s appetite centre (the hypothalamus) to reduce hunger
- Improves blood sugar control by enhancing insulin function
The natural GLP-1 hormone lasts only minutes before being cleared. Ozempic’s effects last for days, providing sustained appetite and blood sugar control.
How Mounjaro works
Mounjaro mimics two hormones:
- Like Ozempic, it activates the GLP-1 receptor
- It also activates a second receptor called GIP (glucose-dependent insulinotropic polypeptide)
This dual-action mechanism likely explains why Mounjaro produces greater weight loss and improvements in blood sugar in clinical trials.1
The additional GIP activation provides extra blood sugar control and appetite management beyond what GLP-1 alone achieves.
Head-to-head clinical evidence
SURPASS-2: Mounjaro vs Ozempic in type 2 diabetes
The SURPASS-2 trial, published in the New England Journal of Medicine, directly compared tirzepatide with semaglutide 1 mg (the standard Ozempic dose) in 1,879 people with type 2 diabetes over 40 weeks.1
Weight loss results at the highest tirzepatide dose:
- Mounjaro 15 mg: -11.2 kg average weight loss
- Ozempic 1 mg: -5.7 kg average weight loss
- Treatment difference: -5.5 kg in favour of Mounjaro
Blood sugar control was also superior with Mounjaro. HbA1c reductions were -2.30% with tirzepatide 15 mg compared with -1.86% with semaglutide 1 mg.1
The proportion achieving clinically meaningful weight loss:
| Weight loss target |
Mounjaro 15 mg |
Ozempic 1 mg |
| ≥5% body weight |
80%1 |
54%1 |
| ≥10% body weight |
57%1 |
24%1 |
| ≥15% body weight |
36%1 |
8%1 |
What about higher doses of semaglutide?
Ozempic’s maximum dose (2 mg) is higher than the 1 mg tested in SURPASS-2, so real-world weight loss on Ozempic may be somewhat greater than the trial suggests.
For context, the SURMOUNT-5 trial compared tirzepatide to semaglutide at weight-loss doses (2.4 mg, the Wegovy dose) in people with obesity.
In that trial, Mounjaro produced 20.2% weight loss compared with 13.7% for semaglutide 2.4 mg over 72 weeks.3
Ozempic’s 2 mg dose sits between the 1 mg tested in SURPASS-2 and the 2.4 mg Wegovy dose tested in SURMOUNT-5. This means Ozempic’s weight-loss potential likely falls somewhere between these two trial results, though it remains lower than Mounjaro in equivalent-dose comparisons.
Side effects and tolerability
Both medications share similar side effects, primarily affecting the digestive system. Most are mild to moderate and improve as your body adjusts.
| Side effect |
Mounjaro (tirzepatide) |
Ozempic (semaglutide) |
| Nausea |
12-18% (dose-dependent)4 |
~20%5 |
| Constipation |
6-17% (dose-dependent)4 |
~5%5 |
| Diarrhoea |
Common during titration4 |
Common during titration5 |
| Vomiting |
Common during titration4 |
Common during titration5 |
Most gastrointestinal side effects occur during dose escalation and reduce significantly over time. The gradual dose titration for both medications is designed to minimise these effects.
In the SURMOUNT-5 trial (comparing these drugs at weight-loss doses), more people discontinued semaglutide due to side effects (5.6%) than tirzepatide (2.7%).3
Neither medication has shown significant safety concerns in clinical trials when prescribed and monitored appropriately. Both require regular follow-up with your prescriber.
Practical differences
Dosing
Ozempic starts at 0.25 mg weekly for four weeks (a titration phase), then increases to 0.5 mg. Your prescriber may increase further to 1 mg or 2 mg, depending on your response.
Mounjaro starts at 2.5 mg weekly for four weeks, then increases to 5 mg. From there, your prescriber can increase your dose to 7.5 mg, 10 mg, 12.5 mg, or 15 mg based on your needs.
Mounjaro’s six dose levels offer more flexibility than Ozempic’s four, allowing finer adjustments to balance effectiveness with tolerability.
Storage
Both should be refrigerated (2-8°C) before first use. Once in use:
- Mounjaro: Room temperature (below 30°C) for up to 21 days
- Ozempic: Room temperature (below 30°C) for up to 56 days
Ozempic’s longer room-temperature window can be a practical advantage for travel or if refrigerator access is limited.
Missed doses
Ozempic: If you miss a dose and there are more than 2 days until your next scheduled dose, take it as soon as you remember. If fewer than 2 days remain until your next dose, skip to your next dose.
Mounjaro: If you miss a dose and there are at least 4 days until your next scheduled dose, take it as soon as you remember. Otherwise, skip to your next dose.
Injection technique
Both medications use pre-filled pens that are straightforward to use. Neither requires priming before each injection. You inject into the skin of your stomach, thigh, or upper arm, rotating sites to avoid irritation.
Cost and access in the UK
For type 2 diabetes
Both medications may be available through the NHS for type 2 diabetes, depending on your local formulary and prescriber recommendations.
On private prescription, typical monthly costs are:
- Ozempic: £150-250 per month, depending on dose and provider
- Mounjaro: £229-349 per month, depending on dose and provider
For weight management
Ozempic is not licensed for weight loss in the UK. Current MHRA guidance is clear that Ozempic should be prescribed only for type 2 diabetes, partly to protect supply for patients living with diabetes.
If weight management is your primary goal, Mounjaro and Wegovy are the licensed options. Mounjaro received NICE approval for weight management in December 2024.2
NHS access is expanding through specialist weight management services, with primary care prescribing rolling out from June 2025.
Who might prefer each option?
Individual responses vary, but certain factors may make one medication more suitable for your situation.
Mounjaro might suit you if:
- You have type 2 diabetes and want stronger blood sugar control – SURPASS-2 showed superior HbA1c reductions at all doses
- Weight loss is a primary goal alongside diabetes management – Mounjaro is the only option licensed for both
- You want the option of higher doses for greater effect – Six dose levels from 2.5 mg to 15 mg
- You’ve tried Ozempic without reaching your goals – The dual-action mechanism offers a different approach
Ozempic might suit you if:
- You have type 2 diabetes and are managing well on it – No clinical reason to switch if you’re happy with your results
- You’ve responded well to GLP-1 medications – Sticking with a familiar, effective treatment has value
- Storage convenience matters – 56 days at room temperature vs 21 days for Mounjaro
- Cost is a factor – Ozempic is typically less expensive on private prescription
Frequently asked questions
Is Mounjaro better than Ozempic for weight loss?
At their respective doses, the clinical evidence clearly favours Mounjaro. The SURPASS-2 trial showed Mounjaro 15 mg produced nearly twice the weight loss of Ozempic 1 mg in people with type 2 diabetes.1
However, Ozempic is not licensed for weight loss in the UK. If weight management is your primary goal, Mounjaro or Wegovy are the appropriate options.
Can I get Ozempic for weight loss in the UK?
No. Ozempic is only licensed for type 2 diabetes in the UK. Current MHRA and NHS guidance states that Ozempic should not be prescribed solely for weight loss, partly to protect supply for patients living with diabetes. Wegovy contains the same active ingredient (semaglutide) at higher doses and is the licensed weight-loss option.
Is Mounjaro or Ozempic better for type 2 diabetes?
The SURPASS-2 trial showed Mounjaro at all three doses reduced HbA1c more than Ozempic 1 mg. Mounjaro 15 mg achieved an HbA1c reduction of 2.30% compared with 1.86% for Ozempic.1
Your prescriber will consider your individual health profile when recommending treatment.
Can I switch from Ozempic to Mounjaro?
Yes. Many people switch for greater weight loss or blood sugar control. You’d have a 7-day washout period between medications, and your prescriber will advise on the appropriate Mounjaro starting dose based on your current Ozempic dose.
Why is Mounjaro more effective than Ozempic?
Mounjaro activates two hormone receptors (GLP-1 and GIP), while Ozempic activates only one (GLP-1). This dual-action mechanism provides additional effects on appetite control, blood sugar regulation, and fat metabolism, which likely explains the greater results seen in clinical trials.1
Are the side effects of Mounjaro worse than Ozempic?
Both have similar gastrointestinal side effects, including nausea, constipation, and diarrhoea. In the SURMOUNT-5 trial (comparing tirzepatide to semaglutide at weight-loss doses), more people discontinued semaglutide due to side effects (5.6%) than tirzepatide (2.7%).3 Side effects typically improve over time with both medications.
Is Ozempic the same as Wegovy?
They contain the same active ingredient (semaglutide) but at different doses for different purposes. Ozempic (up to 2 mg) is used to treat type 2 diabetes. Wegovy (up to 7.2 mg) is for weight management. Wegovy uses higher doses, which produce greater weight loss.
How long do I need to take Mounjaro or Ozempic?
Both are typically used long-term. For type 2 diabetes, treatment continues as long as it remains safe and effective. For weight management with Mounjaro, NICE recommends treatment for at least 12 months.2 Research shows that stopping medication without establishing sustainable lifestyle habits often leads to weight regain.
Can I drink alcohol while taking Mounjaro or Ozempic?
Moderate alcohol consumption is generally fine with both medications. Many people find their tolerance decreases, feeling the effects of alcohol more quickly.
Both medications can cause nausea, and alcohol may worsen this, particularly during dose escalation. If you experience significant nausea, it’s best to limit alcohol until symptoms improve.
Does Mounjaro or Ozempic affect fertility?
Neither medication is recommended during pregnancy or while trying to conceive. Both manufacturers recommend stopping treatment at least 2 months before a planned pregnancy. Discuss timing with your prescriber if you’re planning to start a family.
Take home message
Mounjaro produces significantly greater weight loss and improvements in blood sugar than Ozempic in head-to-head clinical trials.
In the SURPASS-2 trial, Mounjaro 15 mg achieved nearly twice the weight loss of Ozempic 1 mg in people with type 2 diabetes.1
A key distinction is licensing. Ozempic is only approved for type 2 diabetes in the UK, while Mounjaro is approved for both type 2 diabetes and weight management. If weight loss is your primary goal, Mounjaro or Wegovy are the appropriate licensed options.
For those with type 2 diabetes, both medications are effective. Mounjaro’s dual-action mechanism offers additional benefits for both blood sugar control and weight management, though individual responses vary, and Ozempic remains a well-established treatment option.
What matters most for long-term success is not just which medication you take, but the lifestyle changes and support you build alongside it.
Second Nature's Mounjaro and Wegovy programmes
Second Nature provides Mounjaro or Wegovy as part of our Mounjaro and Wegovy weight-loss programmes.
Why choose Second Nature over other medication providers, assuming you're eligible?
Because peace of mind matters.
We've had the privilege of working with the NHS for over eight years, helping people across the UK take meaningful steps toward a healthier, happier life.
Our programmes are designed to meet people where they are, whether that means support with weight loss through compassionate one-to-one health coaching, or access to the latest weight-loss medications (like Mounjaro and Wegovy) delivered alongside expert care from a multidisciplinary team of doctors, psychologists, dietitians, and personal trainers.
At the heart of everything we do is a simple belief: real, lasting change comes from building better habits, not relying on quick fixes. We're here to support that change every step of the way.
With over a decade of experience, thousands of lives changed, and a long-standing record of delivering programmes used by the NHS, we believe we're the UK's most trusted weight-loss programme.
We hope to offer you something invaluable: peace of mind, and the support you need to take that first step.
References
- Frias JP, Davies MJ, Rosenstock J, et al. Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes. N Engl J Med. 2021;385(6):503-515. https://www.nejm.org/doi/full/10.1056/NEJMoa2107519
- National Institute for Health and Care Excellence. Tirzepatide for managing overweight and obesity (TA1026). 2024. https://www.nice.org.uk/guidance/ta1026
- Aronne LJ, Horn DB, le Roux CW, et al. Tirzepatide as compared with semaglutide for the treatment of obesity. N Engl J Med. 2025;393:26-36. https://www.nejm.org/doi/full/10.1056/NEJMoa2416394
- Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide once weekly for the treatment of obesity. N Engl J Med. 2022;387(3):205-216. https://www.nejm.org/doi/full/10.1056/NEJMoa2206038
- Electronic Medicines Compendium. Ozempic 0.25 mg, 0.5 mg, 1 mg solution for injection in pre-filled pen – Summary of Product Characteristics. https://www.medicines.org.uk/emc/product/9748/smpc
