This page puts the four GLP-1 medicines this site covers — Mounjaro, the Wegovy injection, the oral semaglutide "Wegovy pill", and Foundayo — side by side: what each is made of, how it is taken and how often, where it stands with the UK and US regulators, what its own trial reported for weight loss, and how the side effects overlap across the group. It is an honest comparison: there is no "winner", there are no prices, and — importantly — the four have never been tested together, so the weight-loss numbers cannot simply be lined up against one another.

The four at a glance

All four belong to the same broad family — GLP-1 receptor agonists, medicines that mimic a gut hormone to reduce appetite and slow the stomach's emptying[1]. But they are not interchangeable. They involve three different active molecules, made by two different companies, given in two different forms, and they sit at different points on the road from an MHRA licence to NHS access.

Sources: emc Summaries of Product Characteristics, MHRA/GOV.UK, Eli Lilly and Novo Nordisk announcements (see references). A licence date is shown only where our cited sources confirm one; where a cell has no date, the licence is confirmed but a specific date is not stated on this page; where a cell says a status is not documented, our cited sources do not cover it.
  Mounjaro Wegovy injection Wegovy pill Foundayo
Active molecule Tirzepatide Semaglutide Semaglutide Orforglipron
Drug class Dual GIP & GLP-1 receptor agonist GLP-1 receptor agonist (peptide) GLP-1 receptor agonist (peptide) GLP-1 receptor agonist (small molecule)
Maker Eli Lilly Novo Nordisk Novo Nordisk Eli Lilly
Form & route Injection under the skin Injection under the skin Tablet, swallowed Tablet, swallowed
How often Once weekly Once weekly Once daily Once daily
UK licence (weight management) Yes — from 8 Nov 2023 Yes Yes — from 11 Jun 2026 Yes — from 10 Aug 2026 (also licensed for type 2 diabetes)
US licence Type 2 diabetes from 13 May 2022; weight loss under the brand "Zepbound" Not documented in our sources Yes — from 22 Dec 2025 Yes — from 1 Apr 2026

Same family, three different molecules

The most common mistake made about this group is to treat "GLP-1" as one thing. It is not.

Wegovy — both the injection and the pill — contains semaglutide, a peptide GLP-1 receptor agonist made by Novo Nordisk[1][5]. The injection and the tablet are the same molecule delivered two different ways. Our Wegovy injection guide and Wegovy pill guide cover each in full.

Mounjaro contains tirzepatide, made by Eli Lilly. It is not simply a GLP-1 drug: it acts on two gut-hormone receptors — GIP as well as GLP-1 — which is why it is described as a "dual" agonist rather than a plain GLP-1[4][2]. Our Mounjaro guide goes into how that works.

Foundayo contains orforglipron, also from Eli Lilly, and it is different again: it is a small-molecule (non-peptide) GLP-1 receptor agonist[11]. That chemistry is the reason it can be a tablet with no food or water rules, as explained below and on our Foundayo guide. In short, three molecules — semaglutide, tirzepatide and orforglipron — not one.

How each one is taken

Two practical facts separate these medicines more than anything else: injection versus tablet, and weekly versus daily.

Mounjaro and the Wegovy injection are both given as an injection under the skin, once a week[2][1]. The Wegovy injection delivers a maintenance dose of semaglutide 2.4 mg weekly; a higher single-dose 7.2 mg pen was approved by the MHRA on 14 April 2026[12]. Both injectables are started low and stepped up gradually.

The Wegovy pill is a once-daily tablet. Because it is oral semaglutide, it needs to be taken first thing on an empty stomach after an overnight fast, with a wait of at least 30 minutes before eating, drinking anything else or taking other medicines — it is not simply a pill you can take with a meal[18].

Foundayo is also a once-daily tablet, but with a genuine practical difference: according to the manufacturer it can be taken at any time of day, with or without food or water[8]. That freedom is a direct result of its small-molecule chemistry — a non-peptide compound does not need the empty-stomach conditions that oral semaglutide relies on[11]. It is the one clear day-to-day convenience gap in the group — and, since the MHRA authorisation in August 2026, a real one for UK patients rather than a theoretical one. Foundayo comes in six strengths — 0.8, 2.5, 5.5, 9, 14.5 and 17.2 mg once daily — and, like the others, is stepped up gradually, with each step held for at least a month before any increase[19].

Where each stands with the regulators

Licensing is where the four diverge most sharply, and it is worth reading carefully because a licence date is not the same as NHS access.

Mounjaro was first approved in the US for type 2 diabetes on 13 May 2022[4], and gained an EU-wide diabetes authorisation on 15 September 2022[13]. In Great Britain, the MHRA authorised it for weight management in adults on 8 November 2023[3]. One point that often confuses UK readers: in the US the same molecule is also marketed under a different brand name for weight loss, but that separate brand is not sold in the UK — here, weight-management patients are prescribed Mounjaro.

The Wegovy injection is long established for weight management in the UK[1]. The Wegovy pill is far newer: the US FDA approved it on 22 December 2025 as the first oral GLP-1 for weight management[5], and the MHRA approved it on 11 June 2026 as the UK's first GLP-1 tablet for weight loss[6].

Foundayo is the newest. It was approved by the US FDA on 1 April 2026[7], and on 10 August 2026 the MHRA authorised it in the UK — the first regulator in Europe to do so — for weight management in adults with a BMI of 30 or more, or 27 to under 30 with at least one weight-related condition, and also for type 2 diabetes under the same brand[20]. Lilly UK announced on 24 August 2026 that it is available on private prescription[21]. That makes two oral GLP-1 medicines now licensed in the UK for weight management: the Wegovy pill (June 2026) and Foundayo (August 2026).

Licensed does not mean NHS-funded

Foundayo's MHRA licence means it can lawfully be prescribed in the UK — privately, by a qualified prescriber, and dispensed by a GPhC-registered pharmacy. It is not on the NHS: NICE's appraisal of orforglipron (ID6516) is in progress, with publication provisionally expected on 18 November 2026[22]. Any website offering to sell "Foundayo" without a prescription is acting illegally, and whatever it supplies may not be a regulated medicine. If you are checking whether an online seller is legitimate, the government's FakeMeds service explains how to buy medicines safely online. Private prices vary between regulated providers; this page carries none.

What the weight-loss trials show — and why you cannot line them up

This is the section people come for, so it is also the one where honesty matters most. These four medicines have never been tested together in a single trial. Each figure below comes from that medicine's own study, measured against a dummy (placebo) treatment — not against the other three. The trials ran for different lengths, in different groups of people, with different rules. That means you can read each result on its own terms, but you cannot fairly say one number "beats" another.

Headline mean weight change in adults without type 2 diabetes, each from the medicine's own placebo-controlled trial. These are four separate studies and are not directly comparable. Sources in references.
Medicine Trial & length Mean weight change Placebo in the same trial
Wegovy injection STEP 1, 68 weeks[9] About −14.9% About −2.4%
Mounjaro SURMOUNT-1, 72 weeks[10] −16.0% (5 mg) to −22.5% (15 mg) About −2.4%
Wegovy pill OASIS 4, 64 weeks[5] About −16.6% About −2.7%
Foundayo ATTAIN-1, 72 weeks[11] About −12.4% (highest dose) About −0.9%

Three cautions belong with that table, and they are the reason a straight ranking would mislead:

  • The trials measured different people. Weight loss is generally smaller in people who also have type 2 diabetes. In SURMOUNT-2, which tested Mounjaro in adults with diabetes, the mean loss was about −13.4% to −15.7% against −3.3% placebo[3] — noticeably lower than the SURMOUNT-1 figures above, for the very same medicine. Comparing across trials with different populations is not comparing like with like.
  • The same trial can report more than one figure. Companies quote results two ways: an "on-treatment" estimate (the effect while people were actually taking the medicine) and a "treatment-policy" estimate (the effect counting everyone, including those who stopped). The first is always higher. The table uses the higher, on-treatment figure where our sources gave it — for Foundayo, for example, the more conservative measure was about −11.2% rather than −12.4%[11]. Two honest numbers, answering two different questions.
  • There is no head-to-head of all four. Even if two medicines happen to be studied together, that would still not let you rank all four from separate trials. The only fair reading is medicine-by-medicine, against its own placebo.
The honest bottom line

All four produced substantially more weight loss than placebo in their own trials. Beyond that, this page will not tell you which is "strongest", because the evidence does not support that claim for the group as a whole. What matters for an individual — medical history, other conditions, how a medicine is tolerated, and whether it is even available — is a matter for a prescriber, not a league table.

Side effects: a shared, mostly gastrointestinal profile

Here the four are more alike than different. Across the whole GLP-1 class the common side effects are gastrointestinal — nausea, diarrhoea, constipation and vomiting — usually mild to moderate, closely tied to the dose, worst while the dose is being increased, and tending to settle over the following weeks[1]. That shared pattern is exactly why every one of these medicines is started low and stepped up slowly.

Most common side effects, each from that medicine's own trial or its UK product information. The figures were measured differently and are not directly comparable; ranges reflect different dose groups. Sources in references.
Effect Mounjaro (SURMOUNT-1) Wegovy injection (SmPC) Foundayo (ATTAIN-1)
Nausea 24.6–33.3% 43.9% 28.9–35.9%
Diarrhoea 18.7–23.0% 29.7% 21.0–23.1%
Constipation 11.7–17.1% 24.2% 21.7–29.8%
Vomiting 8.3–12.2% 24.5% 13.0–24.0%

The Wegovy pill is not in that table for a simple reason: its trial reported the same gastrointestinal effects as the most common, but our sources did not break out a percentage for each individual symptom at the 25 mg dose[5]. We will not borrow the injection's numbers and present them as the pill's. In the Foundayo trial, the share of people who stopped treatment because of side effects rose with the dose, from 5.3% to 10.3%, against 2.7% on placebo — a reminder that "common and manageable" is not the same as "trivial"[11].

Each medicine also carries its own warnings in its licensed product information, covering rarer but more serious risks such as inflammation of the pancreas, gallbladder problems and dehydration. One point often muddled online: the US prescribing information for these medicines carries a boxed thyroid-tumour warning, but the UK/EU product information for the licensed injectables lists only hypersensitivity as a reason not to use them, and handles the thyroid question as a precaution rather than a ban[1][2]. Do not read a US label as if it were the UK one.

Reporting side effects

If you take any medicine and think it may have caused a side effect, you can report it through the MHRA Yellow Card scheme, and you should speak to your GP or pharmacist. Reporting helps the regulator monitor the safety of these medicines in real-world use.

Getting any of these in the UK

Availability is not the same as licensing, and it is worth setting out plainly. For a medicine to be funded on the NHS, it must pass two separate gates: first an MHRA licence, and then a recommendation from NICE for NHS use. A licence alone does not put a medicine on the NHS.

Mounjaro and the Wegovy injection have cleared both gates but are still tightly rationed: NICE recommends them within defined criteria, and the NHS rollout is phased, starting with those in greatest clinical need[14][15]. The Wegovy pill is MHRA-licensed but would need its own NICE appraisal before any NHS funding. Foundayo has cleared the first gate (MHRA, 10 August 2026) and is at the second: NICE's appraisal is in progress, provisionally expected to publish on 18 November 2026, so for now it is available privately only[22].

Where the NHS route is not open, some people obtain these medicines privately. If they do, the medicine is still prescription-only: it can only be supplied by a GPhC-registered pharmacy after a proper consultation, and a prescriber — not a website — decides whether it is appropriate. This site does not sell, supply or prescribe medicines, and it does not name or link to any provider of them. For plain-English background on any single medicine, use our Mounjaro, Wegovy, Wegovy pill and Foundayo guides, or the broader frequently asked questions.

Frequently asked questions

Which of these four is best for weight loss?

There is no honest single answer, and this page does not pick a winner. The four have never been tested together in one trial, so their results cannot be ranked fairly. Whether any of them suits a particular person depends on medical history, other medicines, tolerance and availability — a decision for a qualified prescriber, not a website.

Can you compare the weight-loss percentages directly?

Not directly. Each figure comes from a separate trial run against placebo, not against the other medicines, and the trials differed in length, design and who took part. For adults without type 2 diabetes, the individual sourced results were: about −14.9% for the Wegovy injection (STEP 1, 68 weeks), −16.0% to −22.5% for Mounjaro (SURMOUNT-1, 72 weeks), about −16.6% for the Wegovy pill (OASIS 4, 64 weeks) and about −12.4% for Foundayo (ATTAIN-1, 72 weeks) — each against its own placebo.

What is the difference between the injections and the tablets?

Mounjaro and the Wegovy injection are once-weekly injections under the skin. The Wegovy pill is a once-daily tablet that, like other oral semaglutide, must be taken on an empty stomach with careful timing. Foundayo is a once-daily tablet that can be taken at any time of day, with or without food or water, because it is a small-molecule (non-peptide) medicine.

Are all four available in the UK?

Yes — all four are now MHRA-licensed: Mounjaro and the Wegovy injection for some time, the Wegovy pill from 11 June 2026 and Foundayo (orforglipron) from 10 August 2026, so the UK has two licensed oral GLP-1 medicines. All are prescription-only and NHS access is narrow and phased: the two injections are NHS-funded only within NICE criteria, and the two pills are currently available on private prescription only.

Do they share the same side effects?

Broadly yes — the common effects across the class are gastrointestinal (nausea, constipation, diarrhoea, vomiting), usually mild to moderate, dose-related and worst while the dose is increasing. Nausea was listed at about 44% in the Wegovy injection SmPC, roughly 25–33% in Mounjaro's SURMOUNT-1 trial and roughly 29–36% in Foundayo's ATTAIN-1 trial. Each medicine also has its own warnings in its product information. Report suspected side effects via the MHRA Yellow Card scheme.

References

  1. electronic medicines compendium (emc). Wegovy 2.4 mg FlexTouch pre-filled pen — Summary of Product Characteristics (semaglutide). medicines.org.uk
  2. electronic medicines compendium (emc). Mounjaro KwikPen — Summary of Product Characteristics (tirzepatide). medicines.org.uk
  3. MHRA / GOV.UK. "MHRA authorises diabetes drug Mounjaro (tirzepatide) for weight management and weight loss" (8 November 2023; includes SURMOUNT-2 data). gov.uk
  4. Eli Lilly and Company. "FDA approves Lilly's Mounjaro (tirzepatide) injection, the first and only GIP and GLP-1 receptor agonist" (13 May 2022). investor.lilly.com
  5. Novo Nordisk. "FDA approves Wegovy (oral semaglutide 25 mg) for weight management" — company announcement, including OASIS 4 results (22 December 2025). novonordisk.com
  6. MHRA / GOV.UK. "First GLP-1 tablet for weight loss approved in the UK" (oral semaglutide, 11 June 2026). gov.uk
  7. Eli Lilly and Company. "FDA approves Lilly's Foundayo (orforglipron), the only GLP-1 pill for weight loss" (1 April 2026). investor.lilly.com
  8. Eli Lilly and Company. "Foundayo — how to take". foundayo.lilly.com
  9. Wilding JPH et al. "Once-Weekly Semaglutide in Adults with Overweight or Obesity" (STEP 1). New England Journal of Medicine, 2021. nejm.org
  10. Jastreboff AM et al. "Tirzepatide Once Weekly for the Treatment of Obesity" (SURMOUNT-1). New England Journal of Medicine, 2022. nejm.org
  11. "Orforglipron, an Oral Small-Molecule GLP-1 Receptor Agonist, in Adults with Obesity" (ATTAIN-1). New England Journal of Medicine, 2025. nejm.org
  12. MHRA / GOV.UK. "Single-dose 7.2 mg semaglutide (Wegovy) pen approved to treat adult patients with obesity" (14 April 2026). gov.uk
  13. European Medicines Agency. Mounjaro — European public assessment report (EU authorisation 15 September 2022). ema.europa.eu
  14. NICE. Technology appraisal TA1026 — tirzepatide for managing overweight and obesity. nice.org.uk
  15. NICE. Technology appraisal TA875 — semaglutide for managing overweight and obesity (recommendations). nice.org.uk
  16. MHRA. Yellow Card scheme — report a side effect. yellowcard.mhra.gov.uk
  17. GOV.UK / MHRA. FakeMeds — buying medicines safely online. fakemeds.campaign.gov.uk
  18. The Pharmaceutical Journal. "MHRA approves semaglutide oral tablets for weight loss" (oral semaglutide administration — empty stomach, overnight fast, 30-minute wait). pharmaceutical-journal.com
  19. electronic medicines compendium (emc). Foundayo (orforglipron) — Summary of Product Characteristics (strengths and dose escalation). medicines.org.uk
  20. MHRA / GOV.UK. "UK first in Europe to authorise orforglipron for weight management and type 2 diabetes" (10 August 2026). gov.uk
  21. Eli Lilly and Company (UK). Press release on the UK availability of Foundayo (orforglipron) on private prescription (24 August 2026). lilly.com/uk
  22. NICE. "Orforglipron for managing overweight and obesity" — technology appraisal in development, ID6516 (GID-TA11650), provisionally expected publication 18 November 2026. nice.org.uk