Foundayo vs Mounjaro: Daily Tablet or Weekly Injection?

Short answer: Foundayo (orforglipron) and Mounjaro (tirzepatide) are both made by Eli Lilly and both licensed in the UK for weight management in adults with a BMI of 30 or above, or 27 or above with a weight-related condition. Foundayo is a tablet you take once a day, at any time, with or without food, and it acts on the GLP-1 receptor; Mounjaro is an injection you give once a week with a KwikPen, and it acts on two receptors, GIP and GLP-1. They have not been compared in the same trial: in separate 72-week trials, counting everyone who started treatment, people lost an average of 11.2% of their body weight on the dose matching Foundayo 17.2mg (ATTAIN-1, New England Journal of Medicine, 2025), against 2.1% on placebo, and 20.9% on Mounjaro 15mg (SURMOUNT-1, New England Journal of Medicine, 2022), against 3.1% on placebo. These were separate trials in different groups of people, so the figures are not a direct comparison. Individual results vary. Which suits you depends on whether you would rather take a daily tablet or a weekly injection, your other medicines and how you get on with it, and a GPhC-registered pharmacist reviews your health before either is supplied.

This guide compares the two as the UK product information (SmPC), the MHRA and the trials describe them, as of October 2026: how each works and is taken, the dose steps, the trial results, side effects, the medicines and contraception rules that apply to each, our prices, and switching between them.

What is the difference between Foundayo and Mounjaro?

The main difference is the form: Foundayo is a daily tablet and Mounjaro a weekly injection, and they contain different medicines that work in slightly different ways. The MHRA authorised Foundayo on 10 August 2026; the background is in our explainer on Foundayo's UK approval.

Foundayo (orforglipron)

A tablet once a day, at any time, with or without food.

Mounjaro (tirzepatide)

An injection once a week, from a KwikPen that holds 4 doses.

How do Foundayo (orforglipron) and Mounjaro (tirzepatide) work?

Both reduce appetite by acting on receptors in the parts of the brain that regulate it, so you eat less: Foundayo through the GLP-1 receptor, and Mounjaro through two receptors, GIP and GLP-1. Both also slow how quickly your stomach empties, which for Foundayo is strongest after the first dose and eases over time.

Orforglipron, the medicine in Foundayo, is a small-molecule, non-peptide GLP-1 receptor agonist. Foundayo is a small molecule that survives digestion on its own, which is why it has no fasting rules at all. Tirzepatide, the medicine in Mounjaro, is a peptide, a chain of amino acids of the kind stomach acid destroys, which is why it is injected. The UK product information says that in studies tirzepatide reduced appetite by increasing feelings of fullness and decreasing hunger and food cravings.

How long each stays in the body explains how often you take it. Orforglipron's half-life, the time it takes for the level in your blood to halve, is about 29 to 49 hours, which suits a daily tablet. Tirzepatide's is about 5 days, which allows a weekly injection. More on each is in how Mounjaro works and our guide to GLP-1 medicines.

How do you take Foundayo and Mounjaro?

Foundayo is one tablet a day, at any time, with or without food; Mounjaro is one injection a week, on the same day each week, at any time of day, with or without meals. This is the counselling we give with each:

Foundayo. One tablet once daily, at any time of day, with or without food. Swallow it whole with water. Never split, crush or chew it. Missed a dose? Take it as soon as you remember on the same day. If you only remember the next day, skip it. Never take two tablets in one day.

Mounjaro. Use a new needle for every injection, and rotate between your abdomen, thigh, and upper arm (for Mounjaro, use the upper arm only if someone else gives the injection). Inject on the same day each week. If you need to move your injection day, you can, as long as at least 3 days (72 hours) pass between two doses. Then inject on your new day each week. Missed dose. Mounjaro: take it if fewer than 4 days have passed, otherwise skip.

Step by step, see how to take Foundayo and how to inject Mounjaro.

How do Foundayo and Mounjaro doses go up?

Both start low and go up in steps: Foundayo from 0.8mg to a highest dose of 17.2mg a day, with at least 30 days on each dose, and Mounjaro from 2.5mg to a highest dose of 15mg a week, with at least 4 weeks on each dose.

Each medicine has its own ladder: a row of this table does not mean the two doses are equivalent. For Foundayo, the UK product information moves you from 0.8mg to 2.5mg and then 5.5mg, each after at least 30 days, and each increase after that depends on how well it is working and how you tolerate it. Never take more than one tablet a day to make a higher dose. You will stay on each dose step for a minimum of 30 days, and we review you before every dose increase.

For Mounjaro, the UK product information moves you from 2.5mg to 5mg after 4 weeks, then, if needed, up in 2.5mg steps after at least 4 weeks on each dose, and your pharmacist reviews you before each increase. Not everyone needs the highest dose of either medicine. Every Mounjaro step is set out in our Mounjaro dosage chart.

Is Foundayo as effective as Mounjaro?

Foundayo and Mounjaro have not been compared in the same trial, so their results cannot be set against each other. Each was tested against a placebo in its own 72-week trial:

In the ATTAIN-1 trial (New England Journal of Medicine, 2025), 3,127 adults with obesity and without diabetes lost an average of 11.2% of their body weight over 72 weeks on the dose matching Foundayo 17.2mg, compared with 2.1% on placebo, counting everyone who started treatment. The trial gave orforglipron as capsules, and the UK product information matches its 36mg capsule to the 17.2mg tablet.

In the SURMOUNT-1 trial (New England Journal of Medicine, 2022), 2,539 adults with obesity, or overweight with a weight-related condition, and without diabetes lost an average of 20.9% of their body weight over 72 weeks on Mounjaro 15mg, compared with 3.1% on placebo, counting everyone who started treatment.

These were separate trials in different groups of people, so the figures are not a direct comparison. Individual results vary.

For any one person, what also matters is whether they can take the medicine as directed, how they tolerate it and what suits their health. Both medicines are licensed alongside a reduced-calorie diet and more physical activity:

Treatment works alongside a reduced-calorie diet and regular activity. Aim for at least 150 minutes a week. Weight loss naturally slows over time, and stopping treatment without keeping lifestyle changes commonly leads to weight regain, so we review you regularly and plan any stop together.

Are Foundayo's side effects different from Mounjaro's?

They are largely the same kind: for both, the most common side effects are stomach and bowel symptoms such as nausea, diarrhoea, vomiting and constipation, mostly mild or moderate and most often while the dose is going up. The UK product information groups them by how often they happen:

Foundayo: Nausea, vomiting, diarrhoea and constipation are common in the first few weeks and after each dose increase. Eat smaller meals, avoid very fatty food, and keep well hydrated.

The product information for each warns about pancreatitis, dehydration from sickness or diarrhoea that can affect the kidneys, low blood sugar with insulin or a sulphonylurea, diabetic eye disease, and food or drink reaching the lungs during a general anaesthetic or deep sedation, and both list gallstones as common. If pancreatitis is confirmed, neither medicine should be restarted. The signs to act on are in the box below. Each medicine has its own guide, with what helps: Foundayo side effects and Mounjaro side effects.

Which medicines and contraception rules apply to each?

Foundayo and Mounjaro are affected by different medicines, and both can make the contraceptive pill less reliable for a while, so each has its own rules.

Foundayo. If you take ketoconazole, itraconazole or clarithromycin, or ciclosporin, the UK product information sets the highest Foundayo dose at 9mg once daily, because these medicines raise the amount of Foundayo in your blood. Others, including St John's wort, can make Foundayo work less well.

Mounjaro. Mounjaro slows how quickly your stomach empties, which can change how tablets are absorbed, most of all when you start and after each dose increase. The product information advises monitoring medicines that need careful dosing, such as warfarin and digoxin, at those times.

Tell us about every medicine you take, including anything you buy without a prescription, and about any new medicine you start. Both medicines can cause low blood sugar alongside insulin or a sulphonylurea (such as gliclazide), and through our service we do not start either for anyone who takes them. GLP-1 treatment with insulin or a sulphonylurea can cause dangerously low blood sugar (hypoglycaemia). This needs to be managed by your GP or diabetes team, who can adjust your existing medicines at the same time.

Neither medicine should be used in pregnancy. If you are planning a pregnancy, the UK product information says to stop Foundayo at least 3 weeks before and Mounjaro at least 1 month before, because of how long each stays in the body. If you become pregnant, stop and contact us or your GP straight away. We do not supply either medicine if you are pregnant, trying for a baby or breastfeeding. Every GLP-1 medicine is covered in our guide to contraception and pregnancy on GLP-1 treatment.

How much do Foundayo and Mounjaro cost?

As of October 2026, Foundayo at Solira is £79.99 for 0.8mg to £139.99 for 17.2mg, for a 30-day pack of 30 tablets, and Mounjaro is £127.99 for 2.5mg to £279.99 for 15mg, for a KwikPen that holds 4 weekly doses. The price depends on the dose:

Prices include VAT. Delivery is £2.99 for tablets, by Royal Mail Tracked 48, and £3.99 for injection pens, by Royal Mail Tracked 24 in insulated packaging. The price for each dose is the same on your first order and every one after. No introductory prices. Every Foundayo strength is in our Foundayo UK price list, and other providers' Mounjaro prices are in our Mounjaro price comparison.

Can you switch between Foundayo and Mounjaro?

Yes, after a pharmacist review. The UK product information for Foundayo and Mounjaro gives no matching dose between the two medicines, so a GPhC-registered pharmacist decides your starting dose. Our consultation asks which medicine you take now, your dose and when you last took it.

Moving between the two also changes the practical rules: a daily tablet instead of a weekly injection, or the other way round, the new medicine's contraception rule from the day you start it, and Foundayo's interaction checks. How switching works with us, from one weekly injection to the other, is in our guide to switching between Mounjaro and Wegovy, and coming back to the same medicine after a gap has its own rules, in restarting after a break.

Foundayo or Mounjaro: which might suit you?

If you are weighing up the tablets, read Foundayo vs Wegovy tablets and Wegovy tablets vs Mounjaro. When you are ready, our weight loss consultation starts with your health and your medicines.