The four options, at a glance

Why you cannot simply compare the headline percentages

You will see these figures set against each other: orforglipron 12.4%, tirzepatide 22.5%, semaglutide 14.9%. Ranked like that, the conclusion looks obvious. It is not a fair comparison, and it is worth understanding exactly why before you weigh it.

Start with the fact that those three figures are not even all the same kind of number — see the third point below.

Different trials, different people. Each figure comes from that medicine’s own trial, with its own participants, entry criteria and baseline characteristics. A trial recruiting people with a higher starting weight, or without diabetes, will tend to produce larger percentage losses regardless of the drug.

Different durations. The orforglipron and tirzepatide figures come from 72-week trials; the semaglutide figure from a 68-week trial. Weight loss on these medicines does not plateau neatly, so length matters.

Different statistical methods. This is the one almost never mentioned, and it moves the numbers substantially. Trials report results two ways. The efficacy estimand asks what happened to people who took the medicine as directed. The treatment-regimen estimand asks what happened to everyone who was randomised, including those who stopped. Orforglipron’s 12.4% is the first kind. On the second, the same trial gives 11.2% — and the placebo group moves too, from 0.9% to 2.1%. The apparent benefit shifts from 11.5 percentage points to 9.1 depending purely on which analysis is quoted. Headlines quote whichever is larger, and rarely say which.

Worse, the three figures above are not even consistent with each other on this point. Orforglipron’s 12.4% and tirzepatide’s 22.5% are both efficacy-type analyses. Semaglutide’s widely quoted 14.9% is the other kind — the comparable efficacy figure from the same trial is 16.9%. So the most commonly reproduced ranking of these three medicines understates one of them by two percentage points for no reason other than which number the press picked up. We have included this page’s figures as they are usually quoted precisely so you can see the problem; they should not be read as a league table.

No head-to-head trial exists between orforglipron and injectable tirzepatide or semaglutide for weight loss. Until one does, cross-trial comparison is the only tool available, and it is a blunt one.

The one comparison that is direct

There is a genuine head-to-head, and it is worth more than all the cross-trial arithmetic combined.

ACHIEVE-3 compared orforglipron against oral semaglutide in people with type 2 diabetes over a year. In that trial, in that population, orforglipron produced greater reductions in HbA1c and greater weight loss than oral semaglutide. It also caused more digestive side effects, and roughly twice as many participants stopped treatment because of them.

That is the shape of the trade-off in the only place we can see it cleanly: more effect, more side effects. It is a reasonable working assumption that this pattern extends beyond the diabetes population, though that has not been demonstrated.

A second study, ATTAIN-MAINTAIN, looked at 376 people who had already lost weight on an injectable and then switched to orforglipron tablets or placebo for 52 weeks. Orforglipron held on to significantly more of the earlier weight loss than placebo in both groups: 79.3% versus 37.6% among those switching from semaglutide, and 74.7% versus 49.2% among those switching from tirzepatide. Both differences were statistically significant.

This is early evidence that a tablet may have a role in holding weight loss achieved on an injection — but it is one study, and it is about maintenance rather than initial loss.

Where the tablets genuinely differ from each other

The more useful comparison for many people is not tablet versus injection but tablet versus tablet, because the two oral options are not equivalent in daily life.

Oral semaglutide has to be taken on an empty stomach after at least eight hours without food, swallowed whole with a small amount of water, followed by a further 30-minute wait before eating, drinking or taking any other medicine. That is a real constraint. It rules out taking it with morning medication, complicates shift work, and is a well-documented reason for missed doses.

Orforglipron has none of these requirements. The MHRA’s authorisation confirms it is taken once daily at any time of day, with no food or water restrictions.

Whether that matters depends entirely on the individual. Some people find the fasting routine straightforward and build it into a morning that already involves waiting before breakfast. Others find it the single hardest part of treatment. It is a difference in what the medicine asks of you, not a claim that one works better than the other, and it is worth raising with a prescriber either way.

Where the injections still have the advantage

Being even-handed about this: the injectables are not simply the old way of doing it.

Larger average weight loss in their own trials. Tirzepatide’s 22.5% is a substantially bigger number than orforglipron’s, and while the cross-trial caveats apply, the gap is wide enough that it is unlikely to be entirely artefact.

Weekly rather than daily. For some people one injection a week is easier to remember than a tablet every day.

Far fewer drug interactions. This is underrated. Tirzepatide and semaglutide are peptides, broken down like proteins, with few interactions. Orforglipron is a small molecule metabolised by the liver enzyme CYP3A4, which brings it into contact with a wide range of common medicines — certain antibiotics, some epilepsy medicines, several statins. It also affects the reliability of oral contraceptives, requiring a non-oral or barrier method for 30 days after starting and after each of six dose increases. For someone on multiple medicines, an injectable peptide may genuinely be the simpler option.

A longer track record. Semaglutide and tirzepatide have been used at scale for years, with correspondingly more real-world safety data. Orforglipron was authorised on 10 August 2026, and the MHRA has said it will keep it under close review.

Broader licences in some cases. Semaglutide injection carries additional UK licensed indications beyond weight management, including cardiovascular risk reduction in certain patients.

Practical differences that get overlooked

Storage. Injectable GLP-1s require refrigeration before use, which affects travel, holidays and anyone without reliable fridge space. Tablets do not.

Needles. Injection pens are designed to be manageable, and most people adapt. But needle aversion is real, and it stops some people starting treatment at all. For them the question is not which medicine produces the larger average result — it is which medicine they will actually take.

Sharps disposal. Injections generate clinical waste requiring proper disposal. Tablets do not.

Time to full dose. Orforglipron’s six steps at a minimum of one month each mean at least five months to the maximum dose. Anyone expecting rapid results in the first weeks has misunderstood how it works.

So which is right?

We are not going to answer that, and you should be wary of any page that does.

The honest position is that these are different medicines with different profiles, and the right choice depends on things a web page cannot know: your medical history, what else you take, whether you have diabetes, how you feel about injections, whether you can keep to a fasting routine, whether refrigeration is practical, what you have tried before and how it went. Those are the inputs, and they are individual.

What this page can usefully do is make sure you arrive at that conversation knowing which questions matter — and knowing that the headline percentage is not the whole story, and in some cases is barely the beginning of it.