What is Mounjaro?
Mounjaro is a prescription-only medicine used for weight management with a reduced-calorie diet and increased physical activity. It is available in the form of an injection to be administered once weekly under the skin.
Mounjaro is a GLP-1 and GIP receptor agonist, which occupies and activates the receptors in the body responsible for the feeling of satiety. It also slows gastric emptying, which can help you feel full for longer. It also enhances insulin release when blood glucose is raised.
What is Wegovy?
Wegovy is a prescription-only medicine used for weight management alongside a reduced-calorie diet and increased physical activity. It is available in the form of a weekly under-the-skin injection as well as a daily oral tablet.
Wegovy is a GLP-1 receptor agonist, which occupies and activates the receptors responsible for the feeling of satiety. It also slows gastric emptying, which can help you feel full for longer.
What is the difference between tablets and injections?
While Mounjaro is exclusively offered as an injectable, Wegovy provides the flexibility of choosing between injectable and oral tablet formats.
Weekly subcutaneous injections are administered under the skin, typically in the upper arm, thigh, or abdomen. For Mounjaro, someone else should help if you inject into the back of your upper arm. Rotating injection sites is recommended to help minimise localised side effects, such as redness, tenderness or discomfort.
Conversely, oral tablets offer a non-invasive alternative that many find more convenient. These are administered daily rather than once a week.
Dosing requirements vary across oral weight management options:
Wegovy Tablets: According to the product information leaflet, these must be taken after a recommended fast of at least 8 hours, on an empty stomach, and swallowed whole with no more than 120 mL of water. Food, drink, and other oral medicines should be avoided for at least 30 minutes post-dose.
Foundayo Tablets: This option provides a more flexible schedule, allowing you to take the prescribed tablet once daily at any time, with or without food.
What oral weight management treatments are available on the market?
Currently, the oral GLP-1 receptor agonists licensed in the UK for adult weight management are Wegovy (semaglutide) and Foundayo (orforglipron) from Novo Nordisk and Eli Lilly, respectively.
Can I switch from Wegovy injection to Wegovy or Foundayo tablets?
Yes, if your prescriber recommends it. Patients established on Wegovy injection at 2.4 mg weekly can be transitioned to Wegovy tablets at 25 mg daily.
Unlike the weekly injectable schedule, the oral form requires daily administration. For this switch, you can take your initial daily Wegovy tablet one week after your final 2.4 mg Wegovy injection, as directed by your prescriber.
If you opt to transition to Foundayo tablets, your prescribing clinician will determine the appropriate starting dose. Since Wegovy and Foundayo contain distinct active ingredients, there is no direct equivalent dose conversion. The recommended starting dose of Foundayo is 0.8 mg once daily. Your prescriber will tell you when to start Foundayo after your last Wegovy injection. Foundayo is taken daily and does not require morning fasting, food, or fluid limitations.
Can I switch from Mounjaro injection to Wegovy or Foundayo tablets?
To transition from Mounjaro injection to Foundayo, ask your prescriber when to start after your last injection. Your prescriber will select the most suitable starting dosage. Due to differences in active ingredients, the recommended starting dose of Foundayo is 0.8 mg once daily, with dose increases at least 30 days apart based on your response and tolerance of potential side effects.
Similarly, your prescriber will advise when to start Wegovy tablets after your final Mounjaro injection. Because these medications contain different active ingredients, direct dose conversion is not possible. Your clinician will determine an appropriate starting dose and gradually increase it based on how well you tolerate the medication.
You must always consult your healthcare provider before switching between treatments.
| Switch from | Switch to | Instructions |
|---|---|---|
| Mounjaro injection | Wegovy tablets | Your prescriber will set the starting dose and tell you when to take the first Wegovy tablet after your last Mounjaro injection. |
| Mounjaro injection | Foundayo tablets | Your prescriber will advise when to start Foundayo after your last Mounjaro injection. The recommended starting dose is 0.8 mg once daily. |
| Wegovy injection | Wegovy tablets | If your prescriber advises switching from 2.4 mg once weekly to 25 mg once daily, Wegovy tablets can start one week after your last Wegovy injection. For other injection doses, ask your prescriber for a plan. |
| Wegovy injection | Foundayo tablets | Your prescriber will advise when to start Foundayo after your last Wegovy injection. The recommended starting dose is 0.8 mg once daily. |
So, which one is better: injections or tablets?
Wegovy injections and tablets contain the same active ingredient, semaglutide. Mounjaro contains tirzepatide and Foundayo contains orforglipron. And although they all target the GLP-1 receptors, Mounjaro targets the GIP receptors as well.
A systematic review and network meta-analysis published in the British Medical Journal in mid-2026 evaluated average percentage body weight reduction in adults with overweight or obesity at one year compared with lifestyle changes alone. The key findings revealed the following outcomes:
| Treatment studied | Mean difference in percentage body weight change at one year vs lifestyle changes alone (percentage points) |
|---|---|
| Tirzepatide injection (Mounjaro) | −14.9 |
| Oral semaglutide (Wegovy tablets) | −10.9 |
| Orforglipron tablets (Foundayo) | −9.9 |
| Semaglutide injection (Wegovy) | −9.8 |
When comparing treatment options, it is essential to keep in mind that individual responses can vary significantly. The study averages cannot predict how much weight an individual will lose after switching.
Side effect profiles also differ depending on how the medication is administered. Localised reactions near the injection site can occur with both Mounjaro and Wegovy injections. Indigestion was reported more often in the Wegovy tablet trial than in the injection trials. Nevertheless, both oral medications and subcutaneous injections share a common set of gastrointestinal side effects, including nausea, vomiting, stomach pain, diarrhoea, and constipation.
Ultimately, selecting the right option depends on clinical suitability as well as personal preference. Certain patients favor the straightforward nature of an oral daily pill, whereas others may find the specific dietary and fasting instructions for Wegovy tablets burdensome, preferring instead the simplicity of a weekly injection.
