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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.
But what actually is Ozempic, and how does it compare to other weight loss injections on the market like Mounjaro?
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.
You may be eligible for weight loss injections privately in the UK through providers like Chemist4U if you:
- Are 18 or older
- Have a BMI of 30 or above (obesity)
- Have a BMI of 27 or above, with a weight-related health condition (like high blood pressure, high cholesterol, or type 2 diabetes)
Check if you might be eligible for weight loss injections with our BMI calculator.
Availability
Both Ozempic (Wegovy) and Mounjaro are available to treat weight loss in the UK through both private prescription and on the NHS.
The NHS criteria for weight loss injections are stricter than the criteria for private prescription through providers like Chemsit4U.
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
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.
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.
What is Ozempic?
Mounjaro Vs Ozempic: The side effects
Semaglutide (Wegovy/Ozempic) side effects are similar to Mounjaro side effects, as both treatments mimic the same hormone. The main difference in the side effect profiles of the two medications is how often particular side effects occur. 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
Mounjaro Vs Ozempic: The cost
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.Mounjaro Vs. Ozempic: Dosing schedules and titration
Even though Ozempic and Wegovy both have the same active ingredient (semaglutide), Ozempic’s titration schedule is different from the Wegovy dosing schedule.
This is because Ozempic is designed to treat type 2 diabetes and Wegovy is designed for weight loss.
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?
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.
Read more about the similarities and differences between Ozempic and Wegovy.
Does Chemist4U prescribe Mounjaro and Ozempic?
However, Chemist4U does prescribe Wegovy, which uses the same ingredient as Ozempic at different doses to target weight loss.
You may be eligible for a private prescription for weight loss injections if you:
- Are over 18 years old
- Are not pregnant or breastfeeding, or planning to become pregnant
- Have a BMI of 30 or higher, or 27 or higher if you have a weight-related health condition
Is Mounjaro the only Ozempic alternative in the UK?
- Saxenda (liraglutide weight loss injections)
- Nevolat (liraglutide weight loss injections)
- Weight loss capsules like Mysimba and Orlistat
Which is stronger Ozempic or Mounjaro?
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.
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.
Final Thoughts
The rise of GLP-1 medications represents one of the biggest shifts in metabolic medicine in decades. Ozempic, Wegovy, Mounjaro, and Zepbound are not miracle drugs, but they are powerful tools supported by serious research.
For people struggling with obesity or type 2 diabetes, they may offer options that simply didn’t exist a few years ago.
Like any medical treatment, the key is using them responsibly, with proper guidance, and with realistic expectations.
The goal isn’t just weight loss. It’s long-term health.
Frequently Asked Questions
1. How long does it take to see results with Ozempic or Mounjaro?
2. Do people regain weight after stopping GLP-1 medications?
Weight regain can happen if lifestyle habits are not maintained. These medications help control appetite, but long-term success usually depends on maintaining healthy eating patterns and regular physical activity after stopping treatment.
