Wegovy® vs Mounjaro®: Which Weight Loss Treatment Is Right for You?

Wegovy® (semaglutide) and Mounjaro® (tirzepatide) are once-weekly weight loss injections approved for use in the UK. In head-to-head clinical trials, Mounjaro® produced greater average weight loss than the 2.4mg dose of Wegovy, but the right choice for you depends on your medical history, tolerance, and even your contraception choices, not effectiveness alone.

Here, we discuss the main differences between Wegovy® and Mounjaro®, including their effectiveness, side effects and cost and how you can switch safely if you feel one may be better for you than the other.

Wegovy® vs Mounjaro®: Key Differences at a Glance

Some of the key differences between Wegovy® and Mounjaro® are shown in the table below:

* Electronic Medicines Compendium (emc). (2026). Wegovy 0.25 mg, FlexTouch solution for injection in pre-filled pen.

** Electronic Medicines Compendium (emc). (2026). Mounjaro KwikPen 10mg solution for injection in pre-filled pen. 

Which is More Effective for Weight Loss?

Based on clinical trial results, Mounjaro® is more effective for weight loss, but the results are comparable. In the SURMOUNT-1 trial, adults with obesity or who were overweight lost, on average, up to 22.5% of their starting body weight on the maximum 15mg weekly dose over 72 weeks. * While on the STEP-UP trial, the average weight loss with the 7.2mg weekly.⁺

Each of these trials also listed how many people achieved at least a 5, 20 or 25% weight loss over 72 weeks for each medication, as shown in the table:

Head-to-head trials comparing the effectiveness of Wegovy® and Mounjaro® exist, but they used only the previously available 2.4mg maximum dose of Wegovy, which may be misleading now that a higher 7.2mg dose is available. That said, the results from the trial found that average weight loss was greater with tirzepatide (Mounjaro®), 20.2%, compared to 13.7% with 2.4mg of semaglutide (Wegovy®) over 72 weeks.ⱽ

Ready for a decision based on your health, rather than trial averages? Start a Hers UK weight loss consultation to see which options a clinician considers suitable. 

* Jastreboff, A. M. et al. (2022). Tirzepatide Once Weekly for the Treatment of Obesity.

⁺Electronic Medicines Compendium (emc). (2026). Wegovy 0.25 mg, FlexTouch solution for injection in pre-filled pen.

ⱽAronne, L. J. (2025). Tirzepatide as Compared with Semaglutide for the Treatment of Obesity.

Dosing and How Each Is Taken

Both weight loss medications are injected under the skin of your stomach, thigh or upper arm once per week. Both start at a low dose and increase gradually to help your body adjust to the active ingredient and reduce the risk of gastrointestinal side effects. You can inject Mounjaro® or Wegovy® at any time of the day, with or without food, as long as you inject it on the same day each week. This helps keep your medication levels consistent in your body and supports its effectiveness. 

Whether you choose Wegovy® or Mounjaro®, you’ll start on the lowest dose and gradually increase your dose, also known as titration, every 4 weeks until you reach the maximum dose or a maintenance dose that suits your needs. Not everyone will need the highest weekly dose of Wegovy® or Mounjaro® for significant, sustainable weight loss.

Wegovy® dosing schedule

Wegovy® is available in 6 doses. Starting with the lowest dose, you’ll follow this dosing schedule until you find a dose that works best for you:

Mounjaro® dosing schedule

Each Mounjaro® pen is pre-filled with 4 doses, 1 per week. Here’s an example dosage schedule:

If you are happy on a lower dose, you can stick with it. There is no need to reach the maximum maintenance dose if you feel you do not need it. Your Hers clinician will discuss your progress, tolerability, and weight loss target throughout your plan, so you can decide which dose is right for you. 

Differences in Price

Wegovy® is cheaper than Mounjaro®. At Hers, Wegovy® plans start from £54/month for a 6-month plan. Mounjaro® starts from £129/month for a 6-month plan. However, this £60 difference is for the starting monthly price and does not necessarily reflect the cost of the full treatment, which depends on several factors, including your maintenance dose and length of treatment. 

A clinician will help you decide which treatment is right for you and consider the affordability of your plan. See Hers UK weight loss plans and discuss ongoing costs with a clinician before choosing a treatment.

How Mounjaro and Wegovy Affect Women's Health

For many women, the choice between Wegovy® and Mounjaro® isn't just about weight loss results - it also depends on how each medication interacts with contraception, pregnancy plans, and conditions like menopause or polyendocrine metabolic ovarian syndrome (PMOS, previously known as polycystic ovarian syndrome). These are worth thinking through before you start treatment, not after.

Family Planning: Pregnancy and Contraception

Neither Wegovy® nor Mounjaro® should be used during pregnancy, while breastfeeding, or if you're actively trying to conceive. If starting a family is part of your plans, the timing matters. If you become pregnant during your treatment, you should stop taking the medication immediately and contact your doctor for advice.

How long should I stop treatment before trying for a baby?

When you need to stop taking your medication if you want to get pregnant depends on the medication:

• For Wegovy®, you should stop taking it at least 2 months before you want to get pregnant*

• For Mounjaro®, stop taking it at least 1 month before you start trying to conceive**

Does Mounjaro® or Wegovy® affect the contraceptive pill? 

Mounjaro® can make the contraceptive pill less effective, especially when you first start weight loss treatment and after each dose increase. UK guidance advises that you should use an additional barrier method, such as condoms, for 4 weeks after starting Mounjaro® and for 4 weeks after each dose increase.*** Alternatively, you can discuss switching to a non-oral contraceptive method, such as the implant or coil, with your GP.

Wegovy® does not carry that same Mounjaro-specific backup instruction. However, vomiting or severe diarrhoea can affect how well an oral pill works, regardless of the cause. Follow your pill’s missed-pill and sickness advice, and ask a pharmacist or contraception service if you are unsure. 

*Electronic Medicines Compendium (emc). (2026). Wegovy 0.25 mg, FlexTouch solution for injection in pre-filled pen.

**Electronic Medicines Compendium (emc). (2026). Mounjaro KwikPen 10mg solution for injection in pre-filled pen. 

***MHRA. (2026). GLP-1 medicines for weight loss and diabetes: what you need to know.

Existing Conditions

If you're managing PMOS or navigating menopause, both are common reasons women consider Wegovy® or Mounjaro® - and both respond, at least in part, to weight management.

PMOS (Polyendocrine Metabolic Ovarian Syndrome)

Mounjaro® and Wegovy® can help with polyendocrine metabolic ovarian syndrome (PMOS) if you are obese or overweight. As insulin resistance can be associated with PMOS, weight management can improve some symptoms, including cycle regularity. However, neither medication is specifically licensed to treat PMOS, so you would still need to meet the eligibility criteria to be prescribed the medication. If PMOS-related weight changes have been particularly difficult to shift, your experience deserves to be taken seriously.

Menopause and Perimenopause

If you have already started menopause, you may have noticed that weight management can feel more difficult at this stage of life. Changes in body fat distribution, sleep, activity and muscle mass can impact your weight. Menopause itself is not a reason for either medication to be prescribed to you, as they are not licensed for this purpose, however, it may be possible to use Wegovy® or Mounjaro® to manage menopause weight gain if you meet the prescribing eligibility criteria. 

One study found that a low 1 mg weekly dose of semaglutide resulted in an average weight loss of 5.8% after 4 months in postmenopausal women, compared with 5.1% in a premenopausal group.* Similarly, a post hoc analysis of the SURMOUNT-1 trial found that the maximum tolerated dose of tirzepatide was associated with significant weight loss across premenopausal (26%), perimenopausal (23%) and postmenopausal (23%) women after 72 weeks.** 

If you're taking HRT, mention it during your consultation so your clinician can take this into account when assessing whether either medication is suitable for you. While HRT is not generally thought to cause weight gain, recent research suggests that taking HRT alongside tirzepatide may be associated with greater weight loss and improvements in some cardiometabolic outcomes compared with tirzepatide alone.***

* Nicolau, J. et al. (2025). Effectiveness of Low Doses of Semaglutide on Weight Loss and Body Composition Among Women in Their Menopause.

** Tchang, B. G. et al. (2025). Body weight reduction in women treated with tirzepatide by reproductive stage: a post hoc analysis from the SURMOUNT program.

*** Castaneda, R. et al. (2026). The role of menopause hormone therapy in modulating tirzepatide-associated weight loss in postmenopausal women with overweight or obesity: a retrospective cohort study.

Potential Side Effects

Side effects are possible with any medication, but they are often mild and can be managed successfully at home, and shouldn’t put you off trying weight loss medication. Wegovy® and Mounjaro® share similar side-effects because they both work in similar ways to help you lose weight.

The main difference is how often certain effects occur. Side effects for both treatments are most common when you first start taking the medication or after a dose increase, and are usually mild and temporary, settling as your body gets used to semaglutide or tirzepatide. 

Wegovy® side effects

The most common Wegovy® side effects are:

• Feeling sick (nausea) (38.9%*)

• Being sick (22.1%*)

• Diarrhoea (24.2%*)

• Constipation (20.4%*)

• Stomach pain (10%**)

• Headache (15.2%**)

• Feeling weak or tired (very common)

Mounjaro® side effects

The most common Mounjaro side effects are***:

• Feeling sick (nausea) (31%)

• Being sick (12.2%)

• Diarrhoea (23%)

• Constipation (11.7%)

• Stomach pain (4.9%)

• Feeling weak or tired (very common)

Despite how common these side effects can be, gastrointestinal side effects led to permanent treatment discontinuation in 3.2% of people taking Wegovy® 7.2mg and 4.3% of people taking Mounjaro® 15mg in clinical trials. Many gastrointestinal side effects can be managed with simple lifestyle adjustments, such as:

• Eating smaller, more frequent meals

• Eating slowly and stopping when you feel full

• Staying hydrated

• Choosing plain, bland, low-fat foods and avoiding spicy, greasy or high-fat foods

In rare cases, Wegovy® and Mounjaro® can cause serious side effects that need urgent attention, such as:

• Severe, persistent abdominal pain, especially if it spreads to your back or comes with vomiting, as this may be a sign of pancreatitis. 

• Gallbladder trouble, such as upper abdominal pain with fever or yellowing of the skin or eyes. 

• Signs of a severe allergic reaction, including swelling of the face or throat or difficulty breathing. 

• Repeated vomiting or diarrhoea that leaves you unable to keep fluids down also needs medical advice.

*Electronic Medicines Compendium (emc). (2026). Wegovy 0.25 mg, FlexTouch solution for injection in pre-filled pen

**Wilding, J. P. H. et al. (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity.

***Jastreboff, A. M. et al. (2022). Tirzepatide Once Weekly for the Treatment of Obesity.

Contraindication: Who Shouldn't Take Wegovy or Mounjaro?

Before prescribing Wegovy® or Mounjaro®, your clinician will use your medical history and current medications to decide whether Wegovy® or Mounjaro® is safe for you. There are some instances which can make these weight loss medications unsuitable for you.

A previous serious allergic reaction to the medication or one of its ingredients is one reason why Wegovy® or Mounjaro® may not be recommended for you. Other health issues call for careful assessment rather than a blanket answer. 

Tell your clinician if you have had pancreatitis, significant gallbladder problems, severe digestive symptoms or suspected gastroparesis (slow stomach emptying). Mention diabetes medications, particularly insulin or sulfonylureas, because combining them with a weight loss medication may increase the risk of low blood sugar and require a change to your diabetes plan. Wegovy also needs particular consideration if you have certain diabetes-related eye problems.

It is best to be open and upfront with your clinician about any health conditions you have or medications you are taking, as this will help them find the most appropriate treatment for you.

The Bottom Line: Is Wegovy or Mounjaro right for you?

Deciding whether Wegovy® or Mounjaro® is right for you will depend on several factors, including your weight loss goals, how your body reacts to the medication, whether you take the contraceptive pill and cost. Both medications have pros and cons that will need to be carefully considered, and your clinician can help. For example, Mounjaro® is associated with greater weight loss, while Wegovy® has a lower starting price, which can be attractive reasons to start the medication.  

Can I Switch Between Wegovy® and Mounjaro®?

You may already be using Wegovy® or Mounjaro® and not seeing the results you expected, experiencing side effects that are difficult to manage, or struggling with the cost of treatment, which may be making you consider switching to another treatment. 

Switching between Wegovy® and Mounjaro® is possible under the guidance of your Hers clinician, but slowing your dosing schedule or reviewing your current dose may be more beneficial than committing to a switch. If you have tried changing your diet, sticking to a lower dose or delaying titration and still think switching is the right option, your Hers clinician can help. Although the Mounjaro® and Wegovy® doses are not equivalent, your clinician will use your current medication dose to help determine which dose you can switch to.

You deserve a recommendation that accounts for life as it is now. Start a weight loss consultation to discuss eligibility, costs, your medical history and which treatment, if any, is appropriate for you.