Foundayo produces about half the average weight loss of Mounjaro
Mounjaro produced an average weight loss of 20.2% over 72 weeks in SURMOUNT-5, the trial where it was directly compared with Wegovy.2
Foundayo produced an average weight loss of 11.2% over 72 weeks in its main trial, ATTAIN-1, compared with 2.1% on placebo.3
You may see Lilly quote a higher figure of 12.4%, the average among people who stayed on the medication for the full trial. This is considered the optimistic outcome, as it’s the average weight loss achieved by those who stay on the medication and adhere to its daily dosing schedule.
We use 11.2%, which includes everyone who joined the trial, because it reflects what tends to happen in a real-world group (where many people stop taking the medication for one reason or another) rather than only those who stayed on it.3
ATTAIN-1 tested an earlier formulation of orforglipron (a capsule) at doses up to 36 mg, whereas the approved tablet has a maximum dose of 17.2 mg.
According to Lilly’s prescribing information, adults without diabetes lost an average of 11.1% of their body weight at 17.2 mg, similar to the result in ATTAIN-1.4
Mounjaro and Foundayo haven’t been directly compared in the same trial, so these figures come from separate studies with different groups of people, and it’s unclear how their outcomes would differ on average.
Still, we can be confident that Mounjaro appears to produce roughly 8-10% more weight loss than Foundayo over the course of the year, on average.
Mounjaro mimics the effects of two hormones involved in appetite and blood sugar control, GLP-1 and GIP, whereas Foundayo mimics GLP-1 alone. This dual-function may partly explain why Mounjaro produced greater weight loss.3
|
Mounjaro |
Foundayo |
| Average weight loss in trials |
20.2% over 72 weeks2 |
11.2% over 72 weeks3 |
| How it’s taken |
Injection once a week |
Tablet once a day |
| Storage |
Unused pens in the fridge |
Original bottle, room temperature |
| Doses |
2.5 to 15 mg |
0.8 to 17.2 mg |
| Monthly cost at Second Nature |
£129 to £329+ |
£129 to £179 |
If you’re still losing weight on Mounjaro
No trial has tested switching to Foundayo while people were still actively losing weight. The switching trial only enrolled people whose weight had plateaued.1
Foundayo produces less weight loss on average, so if you’re still losing weight and working toward your weight-loss goal, switching to Foundayo may stall your progress.2 3
There are still reasons people consider switching at this stage:
- Injection fatigue, or a genuine fear of needles
- Cost, as Foundayo’s monthly prices are significantly lower at all comparable doses in the UK
- Preferring a tablet, particularly for travel or storage
- Have developed healthy habits and feel confident in their ability to keep losing weight with a ‘weaker’ medication
If side effects are why you want to change, switching may not be appropriate.
Both medications cause similar rates of nausea and other gut side effects, and moving to Foundayo gives no guarantee your side effects will ease. If anything, as it’s a new molecule for your body to adjust to, it could make side effects worse.3 4
For most people still losing weight, it’s a reasonable approach to reach your weight-loss goal on Mounjaro first and consider the tablet once you’ve reached it.1
If you simply prefer a tablet and don’t like needles, it’s worth speaking to your prescriber about switching.
However, the
Wegovy pill is also available and supports higher average weight loss than Foundayo and may be a better option if maximum weight loss is your goal.
Now, you may have been on Mounjaro for a while, still have weight to lose, and have developed a healthier lifestyle by adopting habits like eating a diet based on whole foods, exercising more, and building a better relationship with food.
In this scenario, switching to Foundayo is a good option if you don’t need the stronger appetite-lowering effects Mounjaro offers.
Still, instead of switching medications, you can titrate down to a lower dose of Mounjaro and stay there as long as you want.
If you’ve reached your weight-loss goal: what the switching trial found
ATTAIN-MAINTAIN, published in Nature Medicine in 2026, is the first trial to test what happens when people move from a weight-loss injection to a tablet.1
It enrolled 205 people who’d spent 72 weeks on Mounjaro, whose weight had plateaued, and randomly assigned them to either Foundayo or a placebo tablet for a year.1
People who switched to Foundayo maintained 74.7% of their weight loss, while people on the placebo maintained 49.2%.1
In practice, someone who’d lost 20 kg on Mounjaro would, on average, have maintained around 15 kg of it a year after switching.
Even the placebo group maintained around half of their weight loss over the year.1 Lifestyle support continued throughout the trial, which suggests the eating habits people built while losing weight supported weight maintenance, even when coming off the medication.
The trial followed participants for one year, so we don’t know how much of their weight loss they would maintain over a longer period. It also didn’t compare people who switched to Foundayo with those who stayed on Mounjaro, so we don’t know whether the two approaches maintain weight loss equally well.1
Our guide to oral medications for weight maintenance covers the trial in full.
How to switch from Foundayo to Mounjaro
People in the trial took their first Foundayo dose within 14 days of their last injection, with no washout period (a deliberate gap between stopping one medication and starting another).1
They also didn’t start at the lowest dose. The trial started people at the middle doses of orforglipron and increased it every 4 weeks.1
In the first 4 weeks after switching, around 1 in 10 people had gut side effects, and nobody needed their dose reduced.1
The Foundayo tablet on sale uses different dose strengths than the trial, and no conversion between Mounjaro and Foundayo doses has been published.
The licensed doses run from 0.8 mg up to 17.2 mg, with a minimum of a month at each dose.4
You’d communicate with your prescriber to decide whether to increase your dose each month or stay at lower doses, depending on your progress and side effects. Neither the MHRA nor Lilly has published a switching protocol.
If your treatment starts at 0.8 mg and the dose increases each month, you’ll reach the higher doses more slowly than participants in the trial. This might mean you feel hungrier in the first few months as you gradually move to higher doses.
What happens to your appetite when you switch
Tirzepatide has a half-life of around 5 days, so it clears the body gradually over 4 to 6 weeks after your last injection.6 It’s likely you might experience higher hunger levels as the drug slowly leaves your body.
If your prescriber starts Foundayo at a low dose, you might experience higher hunger levels in the first few months on the lower doses before you reach the middle and highest doses, should you need them.
Some hunger and food noise returning during this period is expected and normal, and can be supported by focusing on your eating habits.
We recommend a diet based mainly on whole foods, with three balanced meals a day, each built around half vegetables, a quarter protein, a quarter complex carbohydrates, and a serving of fat.
During weight loss, protein is crucial for maintaining muscle mass, and it also has the biggest impact on reducing hunger compared with the other macronutrients (carbohydrates and fat).
A helpful guide is a portion if protein about the size of the palm of your hand at each meal, which works out to roughly 1.2 to 1.6 grams of protein per kilogram of body weight a day.
If you find yourself struggling with hunger during this period, don’t assume Foundayo isn’t working and speak with your prescriber about what you can do to help maintain lower hunger levels naturally.
What your prescriber will check before switching
Foundayo interacts with some common medicines in ways Mounjaro doesn’t.4 6
- Oral contraceptives: both medications affect how oral contraceptive pills are absorbed. On Foundayo, the advice is to use a non-oral or barrier method for 30 days after starting and after every dose increase. With up to five dose increases, this can apply several times in your first year.
- Simvastatin: capped at 20 mg a day alongside Foundayo. If you take a higher dose, your prescriber will need to adjust your statin first.
- Some antibiotics and antifungals: strong CYP3A4 inhibitors (medicines that slow how the liver clears other drugs) cap Foundayo’s dose at 9 mg
- St John’s wort and some epilepsy medications reduce how much Foundayo reaches the bloodstream, and the advice is to avoid combining them
Apart from the contraception advice, none of these applies to Mounjaro, so they won’t have come up when you started it.6 Take your full medication list, including any herbal supplements, into the switching consultation.
Lilly’s prescribing information also advises against taking Foundayo with any other GLP-1 medication, including Mounjaro.4
Day-to-day differences on Foundayo
The weekly Mounjaro injection is replaced by a Foundayo tablet taken once a day. You can take Foundayo anytime, with or without food. Unlike the Wegovy pill, it doesn’t need to be taken on an empty stomach.4
Foundayo is taken every day, so there are more doses to remember than with Mounjaro.
If you miss a dose, take it as soon as you remember, but don’t take two doses together to make up for it.
If you miss 7 or more doses in a row, your prescriber may restart you at a lower dose.4
Foundayo tablets are sensitive to light, so keep them in their original bottle at room temperature. They don’t need to be refrigerated, while unused Mounjaro pens need to be kept in the fridge.4 6
What switching to Foundayo from Mounjaro costs
At Second Nature, Foundayo costs £129 a month on our monthly plan at the three starting doses, rising to £149 at 9 mg and £179 at the two highest doses.
If you choose a 12-month plan, the monthly price is £25 lower at every dose: £104 for the three starting doses, £124 at 9 mg, and £154 at the two highest doses. The first month is a further £50 off, bringing your first payment to £54, £74, or £104, depending on the dose.
Mounjaro costs £129 to £179 a month at its starting doses and roughly £329 or more at the highest doses.
Someone switching from a higher Mounjaro dose to Foundayo could therefore reduce their monthly cost by about half.
Our Foundayo cost guide includes the full provider breakdown.
If you’re on Wegovy injections
The switching trial also included 171 people who’d lost weight on Wegovy. They maintained 79.3% of their weight loss after switching to Foundayo, compared with 37.6% on placebo.1
If Wegovy is still helping you lose weight and you’re managing the injections well, there’s usually little reason to switch to Foundayo.
Foundayo may be more suitable once you reach your weight-loss goal and want to maintain the weight you’ve lost.
If you’re taking Wegovy, you can also switch to the Wegovy pill instead of changing to Foundayo.
Both the Wegovy pill and injection contain semaglutide, and the pill produces similar weight loss to the 2.4 mg injection. Our guide to switching to the Wegovy pill explains how the two forms compare.
Frequently asked questions
Is Foundayo the same as Mounjaro?
No, though both are made by Eli Lilly. Mounjaro is tirzepatide, a weekly injection that mimics two appetite hormones, GLP-1 and GIP; Foundayo is orforglipron, a daily tablet that mimics GLP-1 alone.3 Foundayo isn’t a tablet form of tirzepatide, and there’s currently no Mounjaro pill.
Can you take Foundayo and Mounjaro together?
No. Lilly’s prescribing information advises against using Foundayo with any other GLP-1 medication.4
How soon after my last Mounjaro injection can I start Foundayo?
In the switching trial, people took their first Foundayo dose within 14 days of their last injection, with no washout period.1
Do I have to start Foundayo at the lowest dose?
Not necessarily, but there’s no published conversion between Mounjaro and Foundayo doses, so your prescriber will recommend which doses to switch you to. Licensed doses range from 0.8 mg to 17.2 mg, with at least a month at each one.4
Will I regain weight if I switch from Mounjaro to Foundayo?
Most people in the switching trial maintained the majority of their weight loss.1
Some regain is possible if you haven’t developed the healthy habits alongside the medication that can lower hunger naturally.
Our free weight regain prevention planner helps you build the habits that prevent weight regain.
Are Foundayo’s side effects different from Mounjaro’s?
They’re similar: nausea, constipation, diarrhoea, and vomiting are the most common on both, mostly mild to moderate and concentrated around dose increases.3 4
In the year after switching from Mounjaro, 23.4% of people on Foundayo reported nausea, compared with 5% on placebo.1
Can I take Foundayo every other day?
No. Foundayo is licensed as a once-a-day tablet, and skipping days would result in less of the drug in your system, and it will be less effective at lowering hunger levels.4
If cost is the reason, ask your prescriber about staying at a lower dose instead; the licence raises the dose based on response, so not everyone moves up to the highest doses.4
Can I switch back to Mounjaro if Foundayo doesn’t suit me?
Yes, under your prescriber’s supervision. There’s no published research on switching back, so expect a conservative approach: your prescriber may restart Mounjaro at a lower dose than the one you were last on, then gradually increase again.
Is Foundayo available on the NHS?
Not yet. It’s private prescription only for now. NICE’s funding decision is expected in November 2026, and our guide to Foundayo and the NHS covers the likely timeline.
Take home message
You can switch from Mounjaro to Foundayo in the UK.
If you’re still losing weight and are tolerating the injections, there’s no clinical reason to switch from Mounjaro to Foundayo.
If you’ve reached your weight-loss goal, the ATTAIN-MAINTAIN trial found that people who switched maintained 74.7% of the weight they’d lost over the following year, compared with 49.2% on placebo.
There’s no official UK switching protocol, so your prescriber will recommend the best option for you based on your progress and side effects.
Foundayo interacts with some medicines that don’t require the same checks with Mounjaro. These include oral contraceptives, simvastatin, and some antibiotics, antifungals, and epilepsy medicines.
Whichever medication you’re taking, the eating habits you develop while you’re taking the medication will likely determine whether you’ll maintain weight loss in the long term.
At Second Nature, we provide Mounjaro and Foundayo, alongside structured habit support from registered dietitians and nutritionists, built around a balanced plate of vegetables, protein, complex carbohydrates, and healthy fats.
A peer-reviewed study published in JMIR Formative Research found that active subscribers on Second Nature’s semaglutide-supported programme lost an average of 19.1% of their body weight at 12 months, with 77.7% achieving at least 10% weight loss.7
Second Nature's Mounjaro and Wegovy programmes
Second Nature provides Mounjaro or Wegovy as part of our Mounjaro and Wegovy weight-loss programmes.
Why choose Second Nature over other medication providers, assuming you're eligible?
Because peace of mind matters.
We've had the privilege of working with the NHS for over eight years, helping people across the UK take meaningful steps toward a healthier, happier life.
Our programmes are designed to meet people where they are, whether that means support with weight loss through compassionate one-to-one health coaching, or access to the latest weight-loss medications (like Mounjaro and Wegovy) delivered alongside expert care from a multidisciplinary team of doctors, psychologists, dietitians, and personal trainers.
At the heart of everything we do is a simple belief: real, lasting change comes from building better habits, not relying on quick fixes. We're here to support that change every step of the way.
With over a decade of experience, thousands of lives changed, and a long-standing record of delivering programmes used by the NHS, we believe we're the UK's most trusted weight-loss programme.
We hope to offer you something invaluable: peace of mind, and the support you need to take that first step.
