Switching from Wegovy to Mounjaro

Wegovy and Mounjaro are injectable weight loss treatments. They’re both used to help people lose weight and maintain weight loss and should be taken alongside dietary and exercise changes that you’d normally follow as part of a weight loss plan. They’re also both taken once a week.

Wegovy contains the active ingredient semaglutide, which is known as a glucagon-like peptide-1 (GLP-1) receptor agonist. It mimics the GLP-1 hormone, which is a naturally occurring hormone released by your body after you eat. Semaglutide sends signals to your brain that you’re full, reducing your appetite and making it easier to follow a diet plan. It also slows down the emptying of your stomach, which means you’ll feel fuller for longer.

Mounjaro contains the active ingredient tirzepatide, another GLP-1 agonist that can reduce your appetite and delay the emptying of your stomach. Tirzepatide also mimics a second hormone called glucose‐dependent insulinotropic polypeptide (GIP) which is believed to further enhance the effects of GLP-1 for appetite suppression.

Semaglutide, the active ingredient in Wegovy, is also found under another name: Ozempic. This is a type 2 diabetic injection that manages blood sugar levels by helping the body produce more insulin. The media have labelled Ozempic as a weight loss drug and it can sometimes be prescribed off-label for this purpose. This is when a medication is prescribed by a doctor for a purpose other than intended, as long as it’s safe to do so. Asda Online Doctor only recommends taking UK-approved weight loss injections.

Mounjaro is also a type 2 diabetes injection found under the same name.

Find out more about the differences between Wegovy, Mounjaro, and Ozempic in our guide.

There are multiple reasons why people switch from Wegovy to Mounjaro:

1. The highest weight loss results in clinical trials are for those taking Mounjaro, but not by much. On the highest maintenance dose (15mg), Mounjaro helped people lose on average 22.5% of their weight after 72 weeks of treatment. On the highest maintenance dose of Wegovy (7.2mg), people lost an average 21% of their weight after 72 weeks.
2. Wegovy was available in the UK before Mounjaro. Some people simply want to try the newer weight loss injection to see if their results are different, or as a personal preference.
3. Wegovy is an effective weight loss medication, although not every person who takes it loses the weight they want to. If this happens, your doctor may recommend switching from Wegovy to Mounjaro to see if your body reacts differently to another active ingredient.
4. Some people want to try the active ingredient tirzepatide instead of semaglutide. Tirzepatide mimics 2 hormones, so although it works in the same way, this may further enhance the effects of the medication.
5. Wegovy and Mounjaro both have side effects, although not everyone will get them. You may want to try Mounjaro if Wegovy is causing severe or ongoing side effects that are not getting better, even at lower doses. Everyone reacts differently to medications, and getting side effects from one medication does not mean you’ll get side effects from another.

Switching from Wegovy to Mounjaro involves a few simple steps, but remember to always follow any specific instructions given by your doctor. Below are the steps you’ll follow if you choose to switch:

1. After discussing this option with your doctor, stop taking Wegovy when your last pen is finished. You may stop straight away if you’re switching due to side effects and do not want to finish your medication.
2. After 7 days, you can start taking Mounjaro. This is the same amount of time you’d usually leave between Wegovy injections, meaning you do not have to ‘wait’ to start Mounjaro. This short break between medications allows enough time for Wegovy to leave your system before starting a new medication.

Even if you were taking Wegovy at the highest dose, you cannot start Mounjaro from a high dose. If you’re on a Wegovy dose of:

• 1mg or less, you’ll start on the lowest dose of Mounjaro, which is 2.5mg
• 1.7 or 2.4mg, you’ll start on Mounjaro’s second dose, which is 5mg

If you have had Wegovy side effects, your doctor may still start you on 2.5mg to avoid any potential severe side effects when starting Mounjaro.

If you’re happy with your Mounjaro weight loss results and you are not getting ongoing or severe side effects, you can continue following the dosage schedule or choose to stay at one of the lower maintenance doses.

You can switch from Wegovy to Mounjaro if you’re eligible to take both medications.

To be eligible, you must:

• be over 18 years old
• have no pre-existing or previous medical conditions that make weight loss injections unsuitable, such as an allergy to the active ingredient
• not be pregnant or breastfeeding
• not be taking any medication that could interact with these weight loss injections and cause severe side effects

You may be able to switch even if you've reached a healthy BMI of 25 or lower.