Ozempic is a brand name for semaglutide used to treat type 2 diabetes. The UK brand name for the medication which uses the same active ingredient (semaglutide), for weight loss treatment is Wegovy.
Mounjaro is currently one of the newer, more popular, weight loss treatments that has been shown to be slightly more clinically effective.
While they both work similarly to help you lose weight, there are some key differences between the treatments, which we’ll cover in this guide. We’ll also explore their active ingredients, safety, weight loss results, and how to switch from one or the other.
Three Key Takeaways
In the UK, Ozempic is only licenced to treat type 2 diabetes. However, the manufacturers, Novo Nordisk, make a medication called Wegovy with the same active ingredient. Wegovy works the same way as Ozempic and is licenced for weight loss treatment in the UK.
The key difference between the two medications is that Ozempic (Wegovy) is single action and mimics a hormone that targets one receptor in the body. Mounjaro is dual-action because its active ingredient targets two receptors.
This dual-action makes Mounjaro slightly more effective than Ozempic (Wegovy). In clinical trials, Mounjaro helped patients lose 22.5% of their starting weight on average, while Ozempic (Wegovy) helped people lose around 21%.
Mounjaro Vs. Ozempic: The similarities and differences
There are a few key similarities and differences between Mounjaro and Ozempic. Let’s explore both:
Similarities
Administration
Both medicines come in the form of a pen filled with medication which patients use to inject themselves once a week.
Effectiveness
Both medicines have been shown in clinical trials to be highly effective at helping people lose weight, with Mounjaro (tirzepatide) helping people lose 22.5% of their starting weight on average, and Ozempic/Wegovy (semaglutide) helping people lose around 21% of starting weight.
Safety
Both medicines have been found in trials to be safe for weight loss treatment, including in the long-term.
Side effects
Both medications share similar common side effects, most of which are digestive, including:
constipation
diarrhoea
nausea
acid reflux (heartburn)
Eligibility criteria
Both medications have similar requirements for you to receive a prescription, both privately and through the NHS.
To receive a prescription of either medication through the NHS you must:
have a BMI of 40 or more (or 37.5 and above for certain ethnic groups)
have at least at least four weight-related health conditions, such as type 2 diabetes, high blood pressure, heart disease, or sleep apnoea
have the medication prescribed through a specialist weight management service
Differences
Licencing
Mounjaro is licenced and approved in the UK for loss treatment.
Ozempic is only licenced in the UK to treat type 2 diabetes. It is only prescribed for weight loss off-label (meaning when a medication is legally and safely prescribed to treat a condition other than that for which it’s licenced.)
Wegovy is a medication made by the same manufacturer using the same active ingredient (semaglutide) as Ozempic, but it’s licenced in the UK for weight loss treatment, and is therefore easier to receive a prescription for.
Active ingredients
Mounjaro’s active ingredient is tirzepatide.
Ozempic’s active ingredient is semaglutide.
Interactions with other medications
Both medications can interact with other drugs, but a recent 2024 study showed that tirzepatide (Mounjaro) is more likely to interact with oral contraception and make it less effective than other weight loss injections, like semaglutide (ozempic/Wegovy).
Mechanisms of action
Ozempic is classed as a GLP-1 agonist, meaning its active ingredient mimics the effects of a hormone called glucagon-like peptide 1 (GLP-1) to activate its receptors.
The effect of this process in the body is to suppress hunger and cause your stomach to empty more slowly, which helps you feel fuller for longer.
Mounjaro is dual-action, meaning it targets two different-hormone receptors, GLP-1 and Gastric inhibitory polypeptide (GIP), both of which affect hunger levels and feelings of fullness. This dual action makes Mounjaro highly effective for weight loss.
Medication
Active ingredient
Dosage
Administration
Licensed for
Available from Chemist4U
Potential weight loss
Ozempic
Semaglutide
Once weekly
Injection
Type 2 Diabetes
No
N/A
Mounjaro
Tirzepatide
Once weekly
Injection
Weight loss, type 2 diabetes
An average of 22.5% over 72 weeks
What’s better for weight loss - Mounjaro or Ozempic?
Neither weight loss medication is ‘better’, it depends on your individual response to the medication and your preferences and priorities with your weight loss treatment.
Technically, Mounjaro is designed for weight loss, whereas Ozempic is designed to treat type 2 diabetes. So Mounjaro could be considered more suitable for weight loss, but it depends on individual response.
In clinical trials, Mounjaro’s active ingredient, tirzepatide, helped people lose 22.5% on average, while semaglutide (Ozempic and Wegovy’s active ingredient) helped people lose around 21% of their starting weight. So, Mounjaro could be considered the more clinically effective medication.
A large-scale study directly comparing tirzepatide to semaglutide also concluded that tirzepatide is more effective for weight loss than semaglutide.
Some people also experience side effects on one medication that they didn’t experience on the other, even if the same side effects are common with both medications.
If you’re taking oral contraception and want to continue taking it rather than switching to external contraception methods, you might prefer semaglutide (Ozempic/Wegovy) over Mounjaro.
Your prescriber can discuss with you which medication will be best for you.
Mounjaro Vs. Ozempic: The clinical trials
Both Mounjaro and Ozempic/Wegovy have been extensively studied in clinical trials for both safety and effectiveness, including in the long term.
Tirzepatide (Mounjaro) has shown slightly better weight loss results than semaglutide (Ozempic/Wegovy) in clinical trials.
In one long-term study, called the SURMOUNT-1 trial, people taking tirzepatide lost up to 25% of their starting weight over a period of 72 weeks.
In a similar study, following the STEP UP trial, people taking semaglutide lost on average 21% of their starting weight over 72 weeks, showing both medications are highly effective for weight loss.
In a 2021 study which directly compared tirzepatide with semaglutide, tirzepatide was found to have slightly higher incidences of troubling side effects.
The study followed patients taking tirzepatide at 5mg, 10mg, and 15mg doses, and patients taking semaglutide at 1mg over 40 weeks.
Throughout the study, a higher percentage of study participants in the tirzepatide groups stopped taking the medication due to adverse events (side effects) than in the semaglutide group.
This means that, overall, tirzepatide is a more effective medication, but can cause more severe side effects, possibly to it being more potent due to its dual-action mechanism.
It helps your body to produce more insulin when it needs it, while at the same time slowing down digestion.
While studying its benefits for diabetes treatment, researchers noticed that patients were experiencing weight loss and appetite suppression, and that semaglutide could therefore be used as a weight loss medication.
Some are more common more with semaglutide (Wegovy/Ozempic), others are more common with Mounjaro.
Side effect
Frequency with Mounjaro
Frequency with Ozempic
Nausea
12% to 18%
16% to 20%
Diarrhoea
12% to 17%
8.5% to 8.8%
Vomiting
5% to 9%
5% to 9.2%
Constipation
6% to 7%
3.1% to 5%
Heartburn
5% to 8%
2.7% to 3.5%
Stomach pain
5% to 6%
5.7% to 7.3%
Serious shared side effects of both medications include:
inflamed pancreas (very rarely)
severe allergic reaction (very rarely)
You should seek urgent medical help immediately if you notice:
severe or prolonged stomach pain
pain that moves to the back
nausea and vomiting
fever
swelling of face, tongue, lips, or throat
trouble breathing or swallowing
severe rash or hives
dizziness
fainting
“All medications can potentially have side effects, and Mounjaro and Ozempic/Wegovy are no different. Most side effects go away on their own as your body gets used to the medicine. But if they don’t, you can always talk to your prescriber for advice.”
Ozempic isn’t licensed in the UK as a weight loss treatment, it’s currently only licensed to treat type 2 diabetes.
However, the manufacturers, Novo Nordisk, make a weight loss injection medicine called Wegovy using semaglutide, the same active ingredient as Ozempic, which works to help with weight loss in exactly the same way.
Wegovy (Ozempic) vs Mounjaro costs:
Wegovy (Ozempic)
Mounjaro
Dose strength 1
0.25mg £99
2.5mg £148
Dose strength 2
0.5mg £109
5mg £198
Dose strength 3
1mg £119
7.5mg £248
Dose strength 4
1.7mg £169
10mg £278
Dose strength 5
2.4mg £199
12.5mg £298
Dose strength 6
N/A
15mg £308
Mounjaro Vs. Ozempic: Dosing schedules and titration
Although tirzepatide and semaglutide work in a similar way in the body, they both have different dose strengths and titration schedules, as they contain different active ingredients.
This is because Ozempic is designed to treat type 2 diabetes and Wegovy is designed for weight loss.
Wegovy (semaglutide)
Ozempic (semaglutide)
Mounjaro (tirzepatide)
Weeks 1-4
0.25mg
0.25mg
2.5mg
Weeks 5-8
0.5mg
0.5mg
5mg
Weeks 9-12
1mg
1mg
7.5mg
Weeks 13-16
1.7mg
2mg
10mg
Weeks 17-20
2.4mg
N/A
12.5mg
Week 21 onwards
2.4mg
N/A
15mg
It’s important to note that the dosing calendar above is based on a typical titration path, but this will look different for everyone.
For some people, staying on a lower dose longer than 4 weeks can help make side effects more manageable, so reaching the higher doses may take longer.
For some people, you may not need the highest dose for weight loss maintenance. Some people will find they’re perfectly able to keep off the weight they’ve lost on a lower maintenance dose. Your prescriber will work with you to assess the right titration schedule and maintenance dose for you.
Can you buy Ozempic or Mounjaro in the UK?
Yes, you can buy Mounjaro in the UK from providers like Chemist4U if our prescribers deem it suitable and safe for you after consultation.
Ozempic is only licensed in the UK to treat type 2 diabetes, but you can buy it under the brand name Wegovy.
Wegovy is the same medication as Ozempic with the same active ingredient (semaglutide), but it’s specifically designed and licenced to treat weight loss, so it comes in different doses.
Is Mounjaro the only Ozempic alternative in the UK?
No, Mounjaro isn’t the only Ozempic alternative in the UK.
The most obvious substitute for Ozempic in the UK is Wegovy, as it’s made by the same manufacturer using the same active ingredient (semaglutide), but it’s designed specifically for weight loss.
But there are many other weight loss medications you may wish to try including:
Neither medication is really ‘stronger’. Although they work in the same way, Ozempic and Mounjaro are different medications with different active ingredients, so it isn’t accurate to compare their dose strengths.
While Mounjaro dose strengths are higher, this doesn’t mean that they’re necessarily stronger; it’s just that the concentration of the active ingredient is different.
Which is safer Mounjaro or Ozempic?
Neither medication is clearly safer than the other. Which one may or may not cause side effects for you will depend on your body’s individual response to either medication.
Both Mounjaro and Wegovy (Ozempic) have been extensively studied in clinical trials and have good safety profiles.
In the SURMOUNT-4 clinical trial, which enrolled 783 adults with obesity to study tirzepatide over a period of 36 weeks, only 53 participants discontinued taking the medication due to side effects.
In a trial of 1,961 adults conducted over 68 weeks, only 4.5% of those taking semaglutide discontinued the medications due to side effects, so both medications are safe for use, including in the long term.
“They’re both relatively safe medicines with good safety profiles. We tend to find that the pros do outweigh the cons. Side effects can be troublesome, but treating obesity is one of the best things you can ever do for your health, and will lower your risk of developing many other health conditions, including heart disease and some cancers. We always advise contacting your prescribing pharmacist if you have side effects that are bothering you or haven’t settled after a few weeks.”
Yes, you can switch from Wegovy (Ozempic) to Mounjaro.
However, semaglutide (the active ingredient in Wegovy) can take a while to leave your system.
Because of this, we recommend you allow up to five weeks after discontinuing Wegovy for the semaglutide this to clear from your body before you start taking any other weight loss medication.
It’s important to remember that you should not take Wegovy and Mounjaro at the same time for safety reasons.
Frequently asked questions about Mounjaro and Ozempic
Is Mounjaro the same as Ozempic?
Mounjaro is a similar medication to Ozempic, but they have different active ingredients. Ozempic is a single action medication that targets one receptor, Mounjaro is dual-action and targets two receptors, making it slightly more effective.
Is Mounjaro stronger than Ozempic?
It isn’t accurate to compare the strengths of Mounjaro and Ozempic because they have different active ingredients which require different amounts to take effect in the body.
Is Ozempic or Mounjaro better for long term use?
Clinical trials have found both Mounjaro and Ozempic to be safe and effective for long-term use. The right medication for you depends on personal preference. Your prescriber can discuss with you which medication might suit you best.
Can I swap from Mounjaro to Ozempic?
Yes, you can switch from Mounjaro to Wegovy (Ozempic). For more information on how to do this, read our full guide on switching from Mounjaro to Wegovy.
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