Key takeaways: switching from Mounjaro to Foundayo
- Different medicines: Foundayo is a newly approved once-daily, non-peptide oral GLP-1 tablet. Mounjaro is a once-weekly dual-action injection.
- Average results: Mounjaro produced higher average weight loss in clinical trials than Foundayo, though individual response varies.
- Why people switch: The usual driver is a needle-free, convenient daily routine rather than greater weight loss.
- Starting dose: Your Foundayo dose depends on your current Mounjaro strength. Patients on higher doses may not need to start from the lowest introductory tablet.
- Clinical review: Foundayo is MHRA-approved. PrivateDoc clinicians confirm whether a switch is safe and appropriate after a successful assessment.
Can you switch from Mounjaro to Foundayo in the UK?
Yes. The Medicines and Healthcare products Regulatory Agency (MHRA) has approved Foundayo for the UK market, and it is now available through PrivateDoc after a clinical review.
You can switch from Mounjaro to Foundayo, but these are prescription-only medicines, so it is not an automatic swap. You will need a medical review with our clinical team to confirm Foundayo is safe and appropriate for your current health status.
How is Foundayo different from Mounjaro?
Both medicines are highly effective treatments manufactured by Eli Lilly, but they work in slightly different ways.
Mounjaro is a once-weekly subcutaneous injection containing tirzepatide. It is a dual-action medication, targeting two appetite hormones (GLP-1 and GIP). That dual action is a significant reason Mounjaro produces such robust weight-loss results.
Foundayo contains orforglipron. It is a once-daily oral tablet and a single-action medicine, targeting the GLP-1 hormone only. Like Mounjaro, it helps you feel fuller and slows digestion, which can make it easier to eat less.
A practical advantage of Foundayo is its formulation. Unlike other oral weight-loss tablets that require strict fasting, such as the Wegovy pill, Foundayo can be taken at any time of day, with or without food.
Mounjaro vs Foundayo at a glance
| Feature |
Mounjaro |
Foundayo |
| Active ingredient |
Tirzepatide |
Orforglipron |
| Format |
Subcutaneous injection |
Oral tablet |
| Frequency |
Once weekly |
Once daily |
| Mechanism |
Dual action (GLP-1 and GIP) |
Single action (GLP-1) |
| Fasting required? |
No |
No |
| Available in the UK? |
Yes |
Yes |
How do the weight-loss results compare?
If you are looking purely at maximum weight-loss potential, Mounjaro currently leads the field.
Because Mounjaro targets two hormones rather than one, it produced higher average weight loss in clinical trials. In the SURMOUNT-1 trial, patients taking the highest dose of Mounjaro lost an average of around 21% of their body weight over 72 weeks, compared with around 3% with placebo.
In the ATTAIN-1 trial for Foundayo, patients taking the highest dose lost an average of around 11% of their body weight over 72 weeks using the treatment-regimen analysis, with headline efficacy estimand results reporting around 12%.
Around one in five patients taking the highest Foundayo dose still achieved at least 20% weight loss, so individual response can vary substantially.
These were separate clinical trials, not direct head-to-head comparisons. Based on the available evidence, Mounjaro appears to offer a stronger average weight-loss effect, although individual response and treatment adherence remain important.
What do real-world results look like?
Trial figures show what is clinically possible, but real-world results depend heavily on consistency and lifestyle changes.
The impressive averages seen in trials only apply to patients who consistently follow a calorie-controlled diet, increase physical activity, and tolerate the highest doses of the medication.
If you switch to Foundayo and find the daily pill much easier to stick to than a weekly injection, better adherence may lead to excellent, sustainable results that rival what you might have achieved on Mounjaro.
Why would you switch from Mounjaro to Foundayo?
For most patients, the decision is driven by convenience, price, and lifestyle. If your primary goal is to lose the maximum amount of weight possible, Mounjaro is likely the better option. Foundayo still offers significant practical benefits.
You might prefer Foundayo if:
- You strongly dislike needles and prefer a simple daily tablet.
- You travel frequently and want a medication that does not require refrigeration.
- You find it easier to build a daily habit than to remember a weekly injection day.
- You have reached your target weight and want a convenient way to maintain progress long term.
You might prefer to stay on Mounjaro if:
- You still have a significant amount of weight you want to lose.
- You are currently tolerating your Mounjaro dose well and seeing good results.
- You prefer only thinking about your medication once a week.
How to switch safely from Mounjaro to Foundayo
Mounjaro and Foundayo use different active ingredients and delivery methods, so you cannot swap doses strength-for-strength.
When switching, PrivateDoc clinicians will assess your current Mounjaro dose, overall progress, and how well you have tolerated treatment so far.
Following the ATTAIN-MAINTAIN clinical trial and guidance from Eli Lilly, your starting Foundayo dose will be tailored to your current treatment level. Because your body has already built up a tolerance to GLP-1 medicines on Mounjaro, you may not need to start from the lowest introductory dose.
As a general guide for patients with mild or no side effects:
| Current Mounjaro dose |
Typical Foundayo starting dose |
| High (10 mg, 12.5 mg, or 15 mg weekly) |
You may be able to transition directly to 9 mg daily |
| Mid-range (5 mg or 7.5 mg weekly) |
Your clinician may start you on 2.5 mg or 5.5 mg daily |
| Low (2.5 mg weekly) |
You will likely start on the introductory 0.8 mg daily dose |
If you have been experiencing moderate or severe side effects on Mounjaro, your clinician will recommend a lower starting dose so your body can adapt more comfortably. Other medicines, medical conditions, and demographic details can also inform the decision.
You typically will not need a long washout period. You can usually take your first Foundayo tablet on the day you would normally have taken your next Mounjaro injection, provided it is within 14 days of your last dose.
Will you regain weight after switching?
Many patients worry that switching from a dual-action injection to a single-action pill will cause immediate weight regain. Early clinical evidence suggests this is unlikely, provided you remain consistent with treatment and lifestyle habits.
In the ATTAIN-MAINTAIN study, patients who switched from injectable incretin-based treatments to Foundayo maintained substantially more of their previous weight loss over 52 weeks than those switched to placebo.
The biggest risk of weight regain is stopping medical treatment entirely, rather than switching format. Staying engaged with the PrivateDoc clinical team and maintaining a healthy diet is the best way to protect your progress.
Managing side effects
Because both medicines act on GLP-1 receptors, they share a very similar side-effect profile.
The most common side effects when starting Foundayo or increasing your dose are gastrointestinal, including:
- Nausea or vomiting
- Diarrhoea or constipation
- Indigestion or stomach discomfort
These symptoms are usually mild and tend to settle as your body adjusts. If you experience severe or persistent side effects, contact the PrivateDoc clinical team for support.
Start planning your next step
Choosing the right weight-management treatment is a personal decision. If you want the daily tablet, start with a free online consultation so our clinicians can review whether a switch from Mounjaro is safe and appropriate for you.
If you would rather continue on Mounjaro for now, you can still complete a weight-loss consultation and discuss your options with a UK-registered prescriber.
