One is the new daily pill awaiting UK approval. The other is the weekly injection with the strongest trial results to date. This page compares them factually — separate trials, honest caveats — because that's the comparison people are actually searching for, and most of what's out there is spin.
Reviewed by Orali · Clinical Lead — a GPhC-registered Pharmacist Independent Prescriber · Last updated 12 June 2026
| Orforglipron (Foundayo) | Mounjaro (tirzepatide) | |
|---|---|---|
| What it is | Small-molecule GLP-1 receptor agonist | Dual GIP and GLP-1 receptor agonist (peptide) |
| How it's taken | Once-daily tablet — any time, with or without food | Once-weekly self-injection pen |
| Average weight loss in trials | ~12.4% over 72 weeks at the highest dose (ATTAIN-1) | ~20%+ over 72 weeks at higher doses (SURMOUNT-1) |
| Common side effects | Both: nausea, vomiting, constipation, diarrhoea — typically mild to moderate, worst around dose increases | |
| Storage | Room temperature | Refrigeration for unopened pens |
| UK status | Awaiting MHRA review — cannot yet be prescribed or supplied | UK-authorised; available via prescription after clinical assessment |
| Maker | Eli Lilly | Eli Lilly |
Trial figures come from separate studies (ATTAIN-1 and SURMOUNT-1) with different designs and populations. No head-to-head trial of these two medicines has been published — treat the numbers as a guide, not a verdict. Individual results vary. Both are prescription-only medicines requiring an individual clinical assessment.
Tirzepatide's ~20%+ average is the strongest result in the field; orforglipron's ~12.4% is meaningful but lower. The caveat: averages from different trials aren't a race result, and the spread between individuals on the same medicine is wider than the gap between these averages.
Mounjaro works on two gut-hormone receptors (GIP and GLP-1), which is thought to underpin its stronger average results. Orforglipron targets GLP-1 alone, but as a small molecule it's simpler to manufacture and take — no needles, no refrigeration, no food or water rules.
Right now in the UK this comparison is partly academic: tirzepatide is available through regulated prescribing after a clinical assessment; orforglipron isn't yet legal to supply. Our UK tracker follows every stage of its MHRA journey.
If maximum average weight loss is the priority and weekly injections don't put you off, the evidence currently favours the injection. If a quiet daily tablet is the difference between starting treatment and not — or between sustaining it and quietly stopping — the pill's lower average may still be the better personal outcome. That trade-off is individual, which is why it belongs in a consultation rather than a comparison table. Our pill vs injection guide goes deeper on the format question itself.
On the available evidence, no — average weight loss in orforglipron's trials (~12.4% over 72 weeks) is lower than tirzepatide's (~20%+ over 72 weeks). But these are separate trials, not a head-to-head, and individual responses on both medicines vary far more than the averages suggest.
Unlikely. They solve different problems: one maximises average effect, the other removes every practical barrier — needles, refrigeration, weekly routines, fasting rules. Most clinicians expect them to coexist, with patient circumstances deciding between them.
Tirzepatide (Mounjaro) is UK-authorised and can be prescribed privately after a clinical assessment of suitability. Orforglipron is awaiting MHRA review and cannot legally be prescribed or supplied in the UK yet — any site claiming otherwise should be avoided. A consultation never guarantees a prescription for any medicine.
That depends on your health, your timeline and how you feel about injections — and it deserves a real conversation rather than a rule of thumb. Waiting has a cost if your weight is actively harming your health now; equally, starting something you won't sustain helps nobody. This is precisely the question a prescriber consultation is for.
Yes — both are Eli Lilly medicines. That's one reason the "pill replaces injection" framing is off: the maker itself positions them as complementary options for different patients.
Tables compare averages; consultations compare your actual health, history and life. Find out where you stand with the free three-minute eligibility check — no payment details, no obligation.
Start the free eligibility checkA consultation never guarantees a prescription — if treatment isn't right for you, we'll say so.