Wegovy vs Mounjaro: Which Weight Loss Injection Is Better in the UK?

Wegovy vs Mounjaro at a glance

Arguably the most popular way to lose weight today is through using weight loss injections. Two often compared treatments currently on the market are Wegovy and Mounjaro. Both can be used to support significant, long-term weight management, but there are some differences.

Wegovy contains semaglutide whereas Mounjaro contains tirzepatide. Both treatments activate the GLP-1 pathway whilst Mounjaro additionally activates GIP. This may influence appetite suppression and weight loss outcomes differently. Both are injectable treatments used once weekly, and due to these similarities, Wegovy is often compared with Mounjaro.

Though not directly compared, data from independent studies can be used to compare the highest doses of Wegovy (at 7.2mg) and Mounjaro (at 15mg). The studies, conducted over 72-weeks, show Wegovy can lead to an average weight loss of 20.7% whereas Mounjaro can lead to 20.2%.

Key differences between the two products:

Mounjaro requires additional contraceptive barrier methods upon initiation and at dose escalations as it may reduce the effectiveness of the oral contraceptive pill. Wegovy does not interact with the pill therefore no additional barrier methods required
*Heart protection: Only Wegovy is approved for cardiovascular risk reduction as shown in the SELECT trial.

What are Wegovy and Mounjaro?

Wegovy, containing the active ingredient semaglutide, belongs to the GLP-1 receptor agonists family of medicines. GLP-1’s mimic the natural gut hormone of the same name. This promotes weight loss by slowing the movement of food through the gut, reducing appetite and signalling early fullness to the brain.

Mounjaro, containing tirzepatide, belongs to the dual GIP and GLP-1 agonist group of medicines. This dual effect provides the same benefits of Wegovy but to a greater extent.

Additionally Mounjaro helps regulate blood sugar by stimulating insulin release. This helps prevent sugar ‘dips’ which can lead to a food craving in between meals, thus controlling appetite further.

Originally licensed for diabetes, Mounjaro was granted approval by the MHRA in November 2023, for weight loss.

How Wegovy and Mounjaro work in the body

We know semaglutide activates the GLP-1 receptors, but what exactly does this do? GLP-1 receptors are found in the gut as well as in the brain, helping to influence appetite regulation.

When activated, GLP-1 links the gut to the brain. Slowing the movement of food whilst telling the brain ‘i’m full’ can lead to an overall reduced food intake, whilst getting the most out of the food already consumed.

Tirzepatide additionally activates GIP receptors, which influence insulin sensitivity. GIP receptors are found in the areas of the brain that control hunger, fullness and energy balance.

When GIP is activated alongside GLP-1, blood sugar levels are more tightly controlled, preventing a sugar dip which can lead to snacking. It can also enhance fullness feelings, helping to reduce appetite further than GLP-1 alone.

Whilst GLP-1 activation lowers blood sugars, GIP activation has a more robust insulin secretion. Activated GIP receptors can improve how tissues respond to insulin and help regulate blood glucose more effectively.

Summary

• Semaglutide activates GLP-1 receptors

• Tirzepatide activates GLP-1 and GIP receptors

• Enhanced insulin secretion after a meal: GLP-1 and GIP

• The brain receives stronger ‘full’ signals which reduce hunger and cravings

• Slower gastric emptying leads to delay in digestion and prolonged fullness

• Increased insulin secretion when blood sugar is high leading to more efficient blood glucose control

Weight loss results: Wegovy vs Mounjaro

Both Wegovy and Mounjaro have great weight loss results in patients, but which one is better?

A side-by-side comparison of semaglutide and tirzepatide shows the following results:

The data shows semaglutide can lead to greater average weight loss and is more likely to help individuals lose up to 25% of their initial body weight. However, tirzepatide led to a greater reduction in waist circumference.

Both treatments additionally help improve blood pressure, blood sugar control and lipid markers, improving cardiovascular health. At present only Wegovy is licensed to reduce the risk of cardiovascular events.

Whilst the results show significant results for both treatments, results may vary between individuals. Some patients may find one treatment works better for them over the other.

Additionally, results are an average and can vary in individuals. Weight loss outcomes depend on lifestyle adherence - incorporating a reduced calorie diet, regular exercise and water intake can all help improve treatment outcomes.

Eligibility and prescribing in the UK

Whilst both treatments are effective, they are not suitable for everyone. As prescription-only treatments, it's the responsibility of your prescribers to make sure only eligible patients are approved for treatment.

The primary criteria assessed for eligibility is BMI, or body mass index which determines obesity classification. This is a ratio of weight in relation to height, and classifies individuals as underweight, healthy, overweight or obese.

BMI is banded as follows:

A BMI over 25 is overweight though this is not the only factor considered. A history of weight-related medical conditions such as type-2 diabetes or cardiovascular disease is considered when prescribing.

Here in the UK, treatments can be obtained from the NHS or from private clinics such as Quick Meds where treatment may be more accessible.

NHS England commissions weight management services. Criteria for NHS prescribing is usually much stricter, prioritizing patients with the highest clinical need. A patient may only be eligible under the NHS, if their BMI is over 40 with multiple weight related medical conditions.

NICE publishes obesity guidelines and sets out eligibility criteria. NHS prescribing sticks very closely to these guidelines offering little wiggle room for patients who are on the borderline of meeting eligibility.

For those who are looking to kick start their weight loss journey, reaching out to a private clinic may be the better option as they have more flexible criteria which are still within the licensed safe parameters. Our clinicians at Quick Meds are optimally placed to provide tailored advice based on your individual needs.

Wegovy and Mounjaro eligibility:

• BMI ≥ 30

• BMI ≥ 27 to 29.9 with a weight related health condition

BMI thresholds are slightly lower for individuals of Asian, Chinese, Middle Eastern, Black African or African-Carribean background.

NHS eligibility varies, reserving treatment for those with the highest clinical need.

• For both Wegovy and Mounjaro

  • BMI ≥ 35

  • BMI ≥30 to 24.9 with a weight related condition.

Based on locality, criteria may be stricter. In Birmingham, the NHS may only prescribe Mounjaro to individuals with a BMI greater than 40 with at least 4 weight-related medical conditions.

Ultimately, the final decision lies with the prescribers clinical decision. As private clinics are not bound by budget restrictions or long waiting lists, they have the flexibility to prioritize patients on an individual risk-benefit assessment, allowing greater access to treatment.

Feel free to contact us for more information of elgibility and see if you are suitable.

Side effects and safety comparison

Wegovy and Mounjaro are generally well tolerated though some patients may experience side effects.

Whilst both semaglutide and tirzepatide may cause gastrointestinal side effects not everyone gets them. These are most common upon initiation of treatment or when the dose is increased. Common side effects are short lived and go away on their own with continued use.

Common side effects include:

• Constipation

• Diarrhoea

• Nausea

• Vomiting

• Gastrointestinal discomfort; cramping, bloating, gas

Another common side effect, though not affecting the gastric system are headaches which are usually a sign of dehydration.

Rarer side effects are pancreatitis, gallstones and a severe allergic reaction.

Signs of pancreatitis include:

• A severe central abdominal pain

• Feeling or being sick

• A fever (of 38°C or more)

Signs of gallstones include:

• A severe stomach pain

• Pain which spreads to the back or chest

• A fever

• Skin or whites of the eyes appear yellow

Signs of an allergic reaction include:

• Swelling of the face, lips, tongue or throat

• difficulty breathing or swallowing

• Wheezing or coughing

• Feeling faint or dizzy

• Skin that feels cold to touch

• Blue, grey or pale lips/skin or tongue

If you experience gallstones, pancreatitis or an allergic reaction, you should stop treatment and seek immediate medical attention.

Both treatments have a similar side effect profile though evidence from studies suggest Mounjaro may be slightly better tolerated.

When initiating, it's important to start at the initiation dose - 0.25mg for Wegovy or 2.5mg for Mounjaro. The dose is then increased no sooner than every 4 weeks until a maintenance dose is reached. Some patients find they do not need to increase as their current dose is helping to achieve desired results.

You should not increase your dose faster than the recommended schedule - doing so may lead to severe side effects and health risks.

Dosing and ease of use

Both Wegovy and Mounjaro are administered as a once-weekly injection subcutaneously (under the skin) into the stomach, thigh or upper arms. The weekly injection helps improve treatment adherence as it is easier than a daily injection or tablets.

For Wegovy, treatment starts at 0.25mg. The dose is increased every 4 weeks until the maintenance dose of 2.4mg or 7.2mg is reached. Some patients find they do not need to increase every month, as they feel the lower dose continues to provide benefits in appetite control.

The newly approved 7.2mg dose is not currently available as a single pen. To inject this dose, patients are required to administer 3 x 2.4mg doses in the same session, once weekly. Doses should be injected into the same area (keeping 5cm apart for each dose), using a new needle for each dose (total of 3 needles for a full 7.2mg dose). This will be updated when the 7.2mg device becomes available.

For Mounjaro, treatment starts at 2.5mg. The dose is increased every 4 weeks, though in this case, every 2nd dose (5mg, 10mg and 15mg) are all licensed maintenance doses.

Cost and access considerations in the UK

Both treatments are prescription-only (POM), requiring clinical assessment with a suitable healthcare professional. This is to make sure you are eligible and the treatment will be safe. This prescription requirement applies to private clinics and the NHS.

Access through the NHS is limited. Due to high demand and limited funding, treatment is reserved for patients with the highest clinical need. Eligibility tends to be stricter, with patients requiring much higher BMIs and multiple weight related co-morbidities.

Private clinics offer wider access. As they are not bound to budgets or waiting lists, eligibility criteria is not as strict, though still within safe parameters. Patients accessing treatment privately can start much sooner, though this is self-funded by the patient.

Whether Mounjaro or Wegovy, the initiation dose attracts the lowest price, with prices increasing with dose. Treatment is generally continued for the mid to long term and is not usually used for short term results.

Long term treatment increases overall cost though, if a patient works alongside their provider, incorporating manageable lifestyle changes in their weight loss journey, the length of treatment and therefore the price can be reduced.

Cost influencing factors:

• Higher doses: Containing more of the active ingredient, attract higher prices.

• Interrupting treatment: Breaks in treatment can affect progress. Treatment may need to be restarted at a lower dose after a break, effectively starting over.

Whilst on treatment it's best to emphasise healthy lifestyle modifications and stay on lower doses as long as they remain effective. Unnecessarily increasing the dose will not lead to faster results though will end up costing more.

Which is better: Wegovy or Mounjaro?

Whilst clinical trials point towards a greater average weight loss with Wegovy, there is no ‘one-size-fits-all’ approach. Treatment choice depends on individual health profiles, ensuring your medical history and goals guide the decision.

Due to the complexity of the treatments, it is essential that weight loss medication is prescribed by healthcare professionals. A clinician can use their judgement to guide you through the process, ensuring you are prescribed the correct medication based on your individual needs.

Ultimately, a thorough clinical assessment determines treatment suitability. This allows a clinician to match the most effective treatment to each individual in a safe manner.

At Quick Meds, the treatment process involves completing an online consultation. This is reviewed by clinicians and followed by a telephone consultation. This allows the clinician to explore the patient's ideas about weight management, the chosen treatment and how to make the most progress, safely.

Who might suit Wegovy

• New patients - only affects 1 treatment pathway

• Where cost is important - Wegovy is more affordable

Who might suit Mounjaro

• Those who require additional support - Mounjaro is a dual action therapy

• Where side effects were troublesome - Mounjaro may have a lower incidence of side effects

Conclusion and Next Steps

Both Wegovy and Mounjaro are effective weight loss treatments, each with distinct mechanisms and prescribing considerations. Treatment outcomes, access and suitability may differ though both have helped individuals attain a healthy weight.

Medical weight loss requires ongoing support, and long term success depends on sustainable habits. Working alongside your healthcare provider to set manageable goals and incorporating healthier lifestyle changes can help you get the most out of your treatment, whether on Wegovy or Mounjaro.