The two most common weight loss injections used in the UK are Wegovy and Mounjaro. In this article, we’ll take a look at some of the similarities and differences between them.
What are Wegovy and Mounjaro?
Wegovy and Mounjaro are two types of treatment that can be used to help some people lose weight by suppressing their appetite and improving how the body uses energy.
They both contain a GLP-1 medication, but one of the main differences between the two treatments is the medicine they contain:
Semaglutide and tirzepatide mimic the natural hormones that are released after eating to help control blood sugars and send satiety (fullness) messages to the brain.
- Semaglutide (Wegovy) mimics one of these hormones – GLP-1
- Tirzepatide (Mounjaro) mimics two of these hormones – GLP-1 and GIP
By mimicking these hormones, semaglutide and tirzepatide can be used to suppress appetite to help with weight loss.
They do this by:
- Increasing feelings of fullness
- Reducing feelings of hunger
- Reducing food cravings
- Improving blood sugar levels
Who can use Wegovy and Mounjaro?
For weight management in adults – that means both weight loss and weight maintenance – Wegovy and Mounjaro injections can be used by the same groups of people. They can only be used in people who have overweight or obesity, which is determined by BMI or Body Mass Index.
Different healthcare providers may have different criteria for prescribing; for example, prescriptions on the NHS are limited to those with higher BMIs and additional weight-related conditions.
At Genwell, we aim to provide an inclusive weight management programme, and so we will consider the following groups for treatment:
- Adults with a BMI of 30 kg/m2 or more
- Adults with a BMI of 25–30 kg/m2 if they have at least one weight-related health problem (e.g., high blood pressure, high cholesterol) or if they are from a higher-risk ethnic group, or if they have been unable to lose weight by any other method previously. See here for details of higher-risk ethnic groups, and see here for a full list of weight-related conditions
The decision of whether to prescribe a GLP-1 medication is one that a healthcare professional will only make if it is appropriate for the individual, after considering all relevant information. At Genwell, a mandatory consultation with a doctor may be required to confirm eligibility for treatment.
Do Wegovy and Mounjaro have the same effectiveness on weight loss?
Most clinical studies of Wegovy and Mounjaro compare the medications to a placebo (dummy injections), but there is one clinical study that compared Wegovy and Mounjaro in people with obesity.
In this study, people used the highest dose of treatment that did not lead to unmanageable side effects (1.7 mg or 2.4 mg of Wegovy and 10 mg or 15 mg of Mounjaro) for 72 weeks. At the end of the study, people taking:
- Wegovy had lost 13.7% of their bodyweight
- Mounjaro lost 20.2% of their body weight
If we look at the other clinical studies, we can see that the weight losses seen vary by the medication and the dose given.
Wegovy up to 2.4 mg dose (for people with overweight and obesity)
- The average weight loss after 68 weeks was ~15% of bodyweight
Wegovy up to 7.2 mg dose (for people with obesity only)
- The average weight loss after 72 weeks was:
- 15.6% of bodyweight for those taking the 2.4 mg dose
- 18.7% of bodyweight for those taking the 7.2 mg dose
Mounjaro up to 15 mg dose (for people with overweight and obesity)
- The average weight loss after 72 or 84 weeks was ~20% of bodyweight
- For the 72-week study, the three doses showed average weight losses of:
- 16% for those taking the 5 mg dose
- 21.4% for those taking the 10 mg dose
- 22.5% for those taking the 15 mg dose
However, you should remember that these figures are all averages. Some people lost less weight, and some people lost more – different people will respond differently to medications.
Do Wegovy and Mounjaro have the same side effects?
Broadly, yes – GLP-1 medications have similar side effects, with the most common being those of the digestive system such as nausea, diarrhoea, vomiting and constipation.
Digestive side effects tend to be worse when starting treatment or increasing the dose, and then improve with time.
When someone starts taking Wegovy or Mounjaro, they will start on a low dose of treatment, then, if they do need to increase the dose, this will be done gradually to help manage these side effects.
For full information on the side effects of the individual medications, including serious side effects, read the information leaflets for Wegovy or Mounjaro.
What our clinical experts say
Whilst side effects can occur, particularly when starting GLP-1 medications, most people find these are manageable with simple adjustments, and they tend to reduce with time. It's important to find a balance between gaining appetite control and eating enough food. There is a risk of going too hard, too quickly and not eating enough to stay strong and healthy or side effects becoming really unpleasant. That's why working closely with a doctor and a wellbeing coach can help you achieve the best experience for you on GLP-1 medications.
Dr Caroline Butler
Is the dosing different between Wegovy and Mounjaro?
Both Wegovy and Mounjaro are given as subcutaneous injections (just below the skin), on a weekly basis. They are both provided in injector pens to make self-injection easier.
Wegovy doses range from 0.25 mg to 7.2 mg, and Mounjaro doses range from 2.5 mg to 15 mg. However, these numbers should not be compared directly because the two treatments contain different ingredients.
Both Wegovy and Mounjaro are started at the lowest dose for at least the first four weeks of treatment. After this, the dose can be increased every four weeks, as needed.
But at Genwell, we follow a structured, doctor-led dosing plan that is designed to support effective, sustainable weight loss while minimising side effects, and this means we don’t always recommend dose increases every four weeks.
Whether your dose is increased will depend on a number of factors, including which medication you are taking, your overall health and your weight loss goals. You can see details of the Genwell dosing plans for Wegovy and Mounjaro here.
- For Wegovy, most people will likely increase to the 1.7 mg or 2.4 mg dose
- For Mounjaro, some people will stay on the lowest dose of 2.5 mg, whereas others may increase to 5mg or 7.5 mg. Higher doses of 10–15 mg are also available
If you are following the Genwell dosing plan, you won’t need to reassess every month unless something needs to change. At the same time, your care remains flexible - your doctor can review and adjust your dose based on how you’re responding, and you can request changes whenever you need to.
At Genwell, we will support each individual in finding the right dose to achieve their goals, alongside providing support with nutrition, exercise, sleep, stress and hormone balance.
At Genwell, we are keen to support patients in finding the right dose for each individual to achieve their goals alongside support with nutrition, exercise, sleep, stress and hormone balance. This may be lower than the licensed maintenance doses for some people.
Can both Wegovy and Mounjaro be used with oral contraceptives?
Neither Wegovy nor Mounjaro should be used in pregnancy, and so it is essential to use contraception if needed. Things to note:
- Wegovy can be used with oral contraceptives
- If using Mounjaro with oral contraceptives, extra precautions should be taken (e.g., using condoms) for 4 weeks after every dose increase.
If someone using oral contraceptives experiences vomiting or diarrhoea while using GLP-1 medications, this can reduce their reliability, and extra precautions should be used.
What are the differences in cost?
The cost of weight loss injections depends on the treatment and dose prescribed. Mounjaro tends to be more expensive than Wegovy, and for both treatments, the costs rise as the dose increases.
Key messages
- Wegovy and Mounjaro are GLP-1 medications used for weight management in adults in the U.K
- They contain different ingredients; Wegovy contains semaglutide, and Mounjaro contains tirzepatide
- They are both effective treatments for weight loss, but clinical study results vary by treatment and dose. A study comparing the two treatments showed that people using Mounjaro achieved greater weight loss.
- They have similar side effects, most commonly affecting the digestive system.
- They are both given as weekly injections, but there are differences between the dosing options for each.
- Mounjaro can affect the reliability of oral contraceptives
- Costs increase as the dose increases; Mounjaro tends to be more expensive than Wegovy
Genwell Reflections
Both Wegovy and Mounjaro are effective treatments to help some people with overweight or obesity lose weight.
The decision to use a GLP-1 medication for weight loss can only be made with a healthcare professional after a full assessment. As with all medications, there will be some cases where a prescription may not be appropriate.
At Genwell, we carry out a holistic review of your weight, overall health and wellbeing before determining whether a GLP-1 medication is right for you, and which one might be the best fit.
We will consider a wide range of factors that could impact your weight loss, and we will work with you to create a personalised journey towards a healthier future.