The Independent Pharmacy

Mounjaro vs Wegovy - How Do They Compare?

Scott McDougall
Scott McDougallMPharmDirector & Registered Manager

Reviewed on 9 Apr 2024

With obesity impacting nearly 30% of the UK adult population, innovative weight management solutions are in high demand. Two of the latest drug treatments showing promise are Mounjaro (tirzepatide) and Wegovy (semaglutide). But with both delivering transformative results, how exactly do they compare? We shall explore Mounjaro vs Wegovy throughout this article.

Mounjaro and Wegovy have made waves for their ability to help UK patients overcome long standing weight loss struggles. Powered by similar mechanisms influencing appetite regulation, the two GLP-1 receptor agonists yield double-digit body weight reduction on average. However, they differ when it comes to indications beyond weight management.

View Mounjaro Weight Loss Treatment

Understanding how Mounjaro and Wegovy align and diverge in their formulas, approvals, clinical backing, and real-world effectiveness empowers UK patients to make an informed treatment decision alongside their doctor. This guide breaks down the key similarities and differences.

Key Findings

  • Mounjaro contains tirzepatide while Wegovy contains semaglutide, which work in different ways. Mounjaro's unique mechanism involves activating both GLP-1 and GIP receptors, whereas Wegovy (semaglutide) activates only the GLP-1 receptor.
  • In trials, on average, Mounjaro users saw a weight reduction of 18.4%, over the course of the 84 week study.[1]
  • Studies on Wegovy found that at 68 weeks, a mean weight loss of 14.9% was present in patients.[2]

What are Mounjaro and Wegovy?

Active ingredients in Mounjaro and Wegovy

The active ingredients in Mounjaro and Wegovy are at the forefront of their weight loss and metabolic management capabilities, yet they significantly differ in their composition.

  • Mounjaro contains the active ingredient tirzepatide, which uniquely activates both GLP-1 and GIP receptors. This dual action targets blood sugar control and weight loss for those with type 2 diabetes or seeking weight management. Mounjaro leverages tirzepatide rather than semaglutide for these dual metabolic benefits.
  • Wegovy's sole active ingredient is semaglutide. This compound specifically activates GLP-1 receptors to reduce appetite and calorie intake, promoting weight loss. In Wegovy, semaglutide mimics natural GLP-1 hormones that regulate appetite. This facilitates weight loss for those struggling with obesity or being overweight with related health conditions.

Indications for Use

Approved uses for Mounjaro

Mounjaro is approved by the UK's Medicines and Healthcare Products Regulatory Agency for weight management, including weight loss and weight maintenance, as an adjunct to a reduced-calorie diet and increased physical activity in adults with an initial Body Mass Index (BMI) of ≥ 30 kg/ m2.

Approved uses for Wegovy

Wegovy, is also approved by the MHRA for long-term weight management. It is sanctioned for chronic administration alongside diet and exercise in adults living with:

  • Obesity (BMI ≥30 kg/m2)
  • Overweight (BMI ≥27 kg/m2) with at least one weight-related comorbidity

Mechanism of Action

How Mounjaro works in the body

As a dual GLP-1/GIP receptor agonist, Mounjaro influences weight and blood sugar via a few key pathways:

  • Increases insulin production which allows better glucose utilisation
  • Lowers glucagon secretion to reduce blood sugar release
  • Delays stomach emptying and intestinal absorption of nutrients
  • Activates regions of the brain linked to appetite to increase feelings of fullness

So in tandem, these effects drive improved glycemic control, appetite reduction, and significant weight loss.

How Wegovy works in the body

Since Wegovy only contains semaglutide, it mainly impacts physiology through one avenue: GLP-1 receptor activation. This yields the following outcomes:

  • Slowed stomach emptying to prolong feelings of satisfaction after meals
  • Increased satiety signals to the brain curbing overall appetite and energy intake
  • Stable blood sugar levels even with lower caloric consumption

While glucagon and insulin activity remain unaffected without GIP, the amplified GLP-1 stimulation allows Wegovy to deliver robust weight management with minimal side effects.

Clinical Trials

Summary of clinical trials conducted on Mounjaro

Mounjaro has been evaluated in six Phase 3 trials involving over 3000 patients with type 2 diabetes. Trial lengths ranged from 24-72 weeks.[1] Key results included:

  • HbA1c reductions between 0.6%-1.9%
  • Proportion of patients reaching HbA1c under 7% as high as 84%
  • Significant weight loss of 13-22 lbs on average
  • BP decreases of 2-7 mmHg

Beyond glucose improvements, over 25% of patients using the highest tested doses lost ≥20% body weight.

Summary of clinical trials conducted on Wegovy

Wegovy has been studied in 4 pivotal trials of nearly 4000 overweight or obese adults without diabetes. Trial durations spanned up to 68 weeks.[2] Notable findings:

  • Average weight loss of 12-15% across all phase 3 trials
  • Proportion losing ≥15% body weight ranging from 34-63% depending on dose & duration
  • Significant reductions in cardiovascular and metabolic disease markers
  • No negative impacts on bone mineral density or renal function

Wegovy delivered weight reductions in line with traditional bariatric surgeries, demonstrating its status as an anti-obesity medication.

Efficacy in Weight Loss

Effectiveness of Mounjaro in reducing body weight

While Mounjaro is not specifically approved for obesity, data from clinical trials showed clear weight loss efficacy alongside blood sugar improvements:

  • Patients lost 13-22 lbs (5-10 kg) depending on dose
  • 27-28% of groups on the highest tested doses achieved 20%+ weight reduction
  • Sustained results over 72 weeks

Initial real-world findings confirm these outcomes translate, with average loss around 15-22 lbs reported so far.

Side Effects

Both Wegovy (semaglutide) and Mounjaro (tirzepatide) can effectively aid weight management. Mounjaro also helps manage type 2 diabetes. However, as with any medication, side effects may occur. Though there are some common side effects due to similar mechanisms of action, each medication also carries unique risks.

Wegovy's side effects may include:

  • Gastrointestinal problems - nausea, vomiting, diarrhoea etc, especially when starting treatment
  • Appetite changes
  • Injection site reactions - redness, swelling, pain

Less common but serious risks involve pancreatitis, gallbladder problems, low blood sugar in diabetics on other medications, kidney dysfunction, and potential thyroid C-cell tumour risk.

Mounjaro's side effects can involve:

  • Likewise gastrointestinal issues, appetite changes, injection site reactions
  • As a dual GLP-1/GIP agonist, side effects may broadly overlap those of GLP-1 drugs but with added considerations due to the dual action

Less common serious risks may also include pancreatitis, gallbladder disease, hypoglycemia for those on diabetic drugs, and kidney problems.

For both treatments, those with a history of thyroid cancer or related genetic markers should use caution and discuss with their doctor, although human risk has not been conclusively shown.

Staying updated on emerging safety data through discussions with one’s healthcare provider is wise when considering these medications.

Choosing The Independent Pharmacy

At The Independent Pharmacy, we recognise the immense burden carried by those struggling with obesity or being overweight. We closely follow innovations like Wegovy and Mounjaro that can aid weight management for appropriate patients. However, we also understand these novel medications are not right for everyone.

Fortunately, our compassionate providers have deep experience applying lifestyle interventions alongside other approved weight loss treatments for those seeking better health. We take a personalised approach - whether that means discussing prescription anti-obesity options, over-the-counter supplements bolstering diet and activity efforts, or developing an integrated plan blending multiple techniques.

Ultimately at The Independent Pharmacy, your wellbeing comes first. We welcome open conversations to understand your unique challenges and priorities when it comes to weight management. Our goal is designing a tailored regimen you feel equipped to maintain. With patience and commitment, we can discover the path that helps you feel your happiest and healthiest. Reach out to initiate that journey today.


Do you offer Wegovy or Mounjaro?

At this time, we do not carry Wegovy or Mounjaro. However, we provide personalised weight loss guidance and scientifically-backed treatments to help patients reach their goals.

Can you explain the difference between Wegovy and Mounjaro?

Wegovy acts only on the GLP-1 receptors while Mounjaro works on GLP-1 receptors and GIP receptors. It is possible that this duel mechanism of action relates to it being a more potent medication to aid weight loss.

Are there any concerns with long-term use of weight loss medications?

This is an important consideration. Medications like Wegovy and Mounjaro are intended for extended use, so maintaining safety with chronic therapy is vital. Potential issues can involve synthesis of vitamin B12, thyroid C-cell changes, kidney problems, and effects on retinopathy.


[1] Mounjaro clinical trial -

[2] Wegovy clinical trial -

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