Mounjaro vs Wegovy for Weight Loss

What are the key differences between Wegovy and Mounjaro?

When comparing the difference between Mounjaro and Wegovy, it's important to understand the shared similarities to notice how they differ. 

The shared similarities include:

• Once weekly injectable medications

• Administered using a pre-filled injectable pen

• Preparing of the pen

• Injection sites are the upper arms, thighs and abdomen

• Wegovy and Mounjaro should be stored in a refrigerator from 2-8°C but in-use pens can be kept at room temperature (up to 30°C) for up to 28 days for Wegovy or 30 days for Mounjaro. Always protect the pens from heat and light, and do not freeze them

The main difference between the medications is the titration schedules and dosage ranges. Mounjaro has 6 dosage levels, starting at 2.5mg, going up to 15mg, while Wegovy has 5 dosage levels, ranging from 0.25mg to 2.4mg.

Ingredients and mechanism

When comparing Wegovy vs Mounjaro, they are both injectable medications that work to support weight loss. However, due to their active ingredients, how they work in the body does differ. 

Semaglutide (the main ingredient in Wegovy) is a single agonist medication that mimics the GLP-1 hormone and it plays a key role in regulating blood sugar and appetite. When the GLP-1 receptors are activated in the pancreas, brain and digestive system, semaglutide helps increase the secretion of insulin when blood sugar levels are high. It also helps to decrease the release of glucagon (a hormone that raises blood sugar), it slows down the rate at which food leaves the stomach and promotes a prolonged feeling of fullness. 

Tirzepatide, (the main ingredient in Mounjaro) is known as a dual agonist because it mimics two hormones: GLP-1 and GIP. The dual action of tirzepatide not only activates the same GLP-1 receptors as semaglutide but also engages GIP receptors and is involved in enhancing the sensitivity of insulin. This dual mechanism leads to greater insulin release, improves the insulin sensitivity and a more noticeable suppression of the appetite compared to GLP-1 agonists alone.

The key difference between Mounjaro and Wegovy is that Mounjaro can lead to greater weight loss due to the dual hormone targeting. By also targeting GIP, tirzepatide not only supports blood sugar regulation but when combined with GLP-1, it's been shown to provide better glycaemic control than the GLP-1 hormone alone.

Clinical results and effectiveness

Both Wegovy and Mounjaro have been studied in clinical trials to assess their effectiveness in weight loss and blood sugar control. The table below highlights the weight loss achieved from these studies for people with and without type 2 diabetes.

Looking at the difference between Mounjaro and Wegovy for weight loss, Mounjaro consistently produced greater results, particularly in people without diabetes. These outcomes reflect both the dual hormone mechanism of tirzepatide and its enhanced impact on glycaemic control.

How do I take Mounjaro or Wegovy?

Both Mounjaro and Wegovy are once weekly injections and they come in easy to use injection pens. Always read before using and follow the instructions provided with your device.

Preparing for Your GLP-1 Injection

Whether you're using Mounjaro or Wegovy, the preparation steps are similar:

1. Wash your hands thoroughly with soap and warm water

2. Clean the injection site with warm soapy water

3. Check to make sure you are taking the correct medication and dose
   a. Ensure it’s not expired or damaged
   b. Confirm the medication is clear (Mounjaro may be slightly yellow, Wegovy should be colourless)

4. Attach a new needle securely by twisting it into place

5. Remove the outer and inner needle caps, but keep the outer cap for safe disposal later

Using a Mounjaro Pen

6. Attach a new needle securely by twisting it into place and wipe the red inner seal with a swab

7. Remove the outer and inner needle caps, but keep the outer cap for safe disposal later

8. Turn the dose knob until you hear two clicks and see the extended line in the dose window

9. Hold the pen upright and gently tap to move any air bubbles to the top

10. Push the knob until a small amount of medicine is released. Wait 5 seconds, your pen is now primed

11. Insert the needle

12. Inject the medication by pushing down the knob slowly for 5 seconds

13. Check the dose window shows 0 to confirm the full dose was delivered
a. If not, reinsert the needle and complete the dose without redialling

Using a Wegovy Pen

14. Attach a new needle securely by twisting it into place

15. Remove the outer and inner needle caps, but keep the outer cap for safe disposal later

16. Twist the pen to the flow check symbol (2 dots and a line) if it's a new pen

17. Press the button and if a drop appears at the tip, the pen is ready
a. If no drop appears, repeat the flow check (up to 2 more times)

18. Turn the dose selector until the dose counter stops, and it shows your prescribed dose

19. Insert the needle into your chosen injection site

20. Press and hold down the dose button until the dose counter shows 0. Keep pressing the dose button with the needle in your skin and slowly count to 6. The 0 must line up with the dose pointer. You may hear or feel a click when the dose counter returns to 0.

After the Injection

21. If there is any bleeding, press a cotton ball gently over the site

22. Place the outer needle cap back on and unscrew the needle

23. Dispose of the used needle in a sharps container

24. Replace the pen cap and store your medication according to the manufacturer’s instructions (usually in the fridge)

Where to inject Mounjaro or Wegovy

Mounjaro and Wegovy can be injected into the tummy, thigh or upper arm (if you choose the back of the upper arm, get someone to help you). You can inject in the same area each time, but not the same exact spot.

After injecting your Mounjaro medication, there are a few steps to take:

1. If there is any bleeding at the injection site, gently press with a cotton wool ball until it stops

2. Place the outer needle shield back onto the pen

3. Unscrew the capped needle and dispose of it in your sharps container

4. Replace the pen cap and store the pen safely for your next use

Costs of Wegovy vs Mounjaro

The cost of Wegovy and Mounjaro can vary depending on the medication, prescribed dose and whether it is obtained through the NHS or a private service. Both Wegovy and Mounjaro are available on the NHS for eligible patients who meet specific criteria and they can also be accessed privately with a prescription.

In private clinics and pharmacies, prices differ by dose strength and provider, with additional fees sometimes applied for consultations or support services. Both medicines are supplied only after a clinical assessment to ensure suitability and safe prescribing. Below is our cost of both Mounjaro and Wegovy.

Side effects of Mounjaro vs Wegovy

Both Mounjaro and Wegovy share many common GLP-1 side effects but each medication may also cause some side effects unique to the active ingredient and hormone targeting. Understanding these differences can help you better prepare and recognise what to expect.

If you experience serious side effects such as pancreatitis, anaphylaxis or severe dehydration, phone 999 for immediate medical attention. 

Many of the common side effects increase during the beginning of the treatment or when doses are increased. These side effects can be managed and will often go away on their own in time. 

If your side effects become prolonged or they cause a disruption to your daily life, please read the patient information leaflet for Mounjaro and Wegovy or contact your clinician. They can help you manage symptoms effectively or adjust your treatment if needed.

Which medicated weight loss treatment is right for me?

Choosing the right weight loss medication depends on several factors, including your goals, medical history and your suitability. It’s important to consider how each medication aligns with your lifestyle and treatment preferences.

The best way to find out whether Mounjaro or Wegovy is the right option for you, is to speak with a clinician. A consultation with them can help tailor the treatment plan to your specific situation to ensure safe and effective care.

Who can't take Mounjaro or Wegovy?

Mounjaro and Wegovy are generally safe and effective when prescribed appropriately but they’re not suitable for everyone. There are specific health conditions where the risks may outweigh the benefits and they include those with:

• A history of pancreatitis - inflammation of the pancreas.

• People with known allergies to semaglutide, tirzepatide, or any of the ingredients in the medication

• Severe gastrointestinal disease (such as gastroparesis) - these medications slow down stomach emptying, which can worsen symptoms in people with certain digestive conditions.

When having your consultation with our clinician, it is important to tell them about your medical history. This is to help determine which medication is safe and appropriate for you.

Interactions with other medicines

GLP-1 medications can interact with other medications, which may affect how well Mounjaro or Wegovy work and it could increase the risk of side effects. It's important to tell your clinician about all the medications you’re taking, including prescriptions, over the counter medicines, supplements or herbal remedies.

Some common medications that may interact with Mounjaro or Wegovy include:

• Insulin or other diabetes medications - the combinations can increase the risk of low blood sugar (hypoglycaemia), especially when doses do not get adjusted

• Anticoagulants (such as warfarin) - require close monitoring due to possible changes in how the drug is metabolised

Medications that may interact with Wegovy specifically:

• Salicylates (such as aspirin) - may increase gastrointestinal side effects

• Some antacids and indigestion remedies - may interfere with how the medication is absorbed or tolerated

• Certain antibiotics - especially those that affect gut function, which may alter how semaglutide is processed

• Antidepressants - Some may affect appetite, weight or blood sugar levels. May influence the effectiveness or side effects of the weight loss medication

Medications that may interact with Mounjaro specifically:

• Thyroid medications (such as levothyroxine) - Slowed gastric emptying may influence how thyroid hormones are absorbed, requiring monitoring.

This is not a full list of possible interactions. Always check with your clinician before starting or stopping any medication while using Mounjaro or Wegovy.

Can I switch from Mounjaro to Wegovy?

Yes, you can switch from Mounjaro to Wegovy. You will need to have a consultation to know that the medication is suitable for you. Many people are exploring alternatives due to the availability of weight loss injections but the choice depends on individual needs, goals and how your body responds to the medication.

Get the right support for your weight loss journey

Thinking about medical support for weight management? Book a consultation with a clinician. We’ll review your health, discuss non-medicine options, and consider licensed treatments only if clinically appropriate and in line with UK guidance.

Advice and information to support weight loss