Orforglipron vs semaglutide: how the two molecules differ

Searches for orforglipron vs semaglutide usually ask whether Foundayo, the once-daily tablet, is simply semaglutide in pill form. It is not. Both switch on the same receptor but are different kinds of molecule, and that fact explains most of what separates them: dosing, duration, interactions and how to read the trial results.

This is information only, not medical advice. Both are prescription-only medicines; whether either suits you is a decision for a qualified prescriber.

Orforglipron vs semaglutide at a glance

Two molecules, one receptor

GLP-1 is a gut hormone released after meals: it prompts insulin when blood sugar is high, slows stomach emptying and acts on the brain's appetite centres. Both medicines activate its receptor.

Semaglutide: the hormone, rebuilt to last

Semaglutide is a GLP-1 analogue — a chain of amino acids sharing 94% of the human hormone's sequence, stabilised against the DPP-4 enzyme and given a fatty-acid side chain that binds to albumin. Its UK Summary of Product Characteristics (SmPC) gives a half-life of around one week, hence weekly dosing.

Orforglipron: a small molecule, not a peptide

Orforglipron's SmPC calls it an oral, high-affinity, non-peptide GLP-1 receptor agonist: a small molecule that digestion does not destroy as it would a peptide. Its half-life of about 29 to 49 hours suits once-daily dosing, and it is cleared mainly by the liver enzyme CYP3A4, which matters for interactions. Our explainer on how orforglipron works goes deeper.

Why the chemistry changes how each is taken

A peptide swallowed on its own is largely digested, so semaglutide comes mainly as a weekly injection, stepped up from 0.25 mg over 16 weeks to the usual 2.4 mg maintenance dose, with a 7.2 mg option for obesity. The oral Wegovy tablet, authorised in June 2026, gets round digestion with an absorption enhancer and a strict routine: an empty stomach after at least eight hours' fasting, no more than 120 ml of water, then a 30-minute wait before food, drink or other tablets.

Orforglipron needs none of that: its SmPC allows any time of day, with or without food. The ladder runs 0.8, 2.5 and 5.5 mg, with optional steps to 9, 14.5 and 17.2 mg at least 30 days apart. Unopened Wegovy pens live in the fridge; Foundayo tablets stay in their blister at room temperature. See our dosage page and how to take Foundayo.

What the trials found — and what they cannot tell you

In STEP 1, semaglutide 2.4 mg produced around 15% average weight loss over 68 weeks in adults without diabetes; the 25 mg tablet 13.6% over 64 weeks in OASIS 4. In ATTAIN-1, orforglipron's highest strength produced 12.4% over 72 weeks against 0.9% on placebo, according to the UK licence.

Different trials, participants and durations make this an indirect comparison, not a ranking. The only head-to-head is in type 2 diabetes: ACHIEVE-3, a 52-week open-label study of 1,698 adults on metformin, compared orforglipron with oral semaglutide at diabetes strengths (7 and 14 mg). At the top doses, according to the UK licence, HbA1c fell by 2.2 percentage points versus 1.4 and body weight by 9.2% versus 5.3%, but gut side effects, and stopping because of them, were commoner on orforglipron. It says nothing about weight-management doses. Our trial results article and development page cover the full programme.

Side effects and interactions: shared pattern, different details

Because both activate the same receptor, the common side effects match — nausea, vomiting, diarrhoea and constipation, worst when a dose starts or rises and easing over time. Both SmPCs list pancreatitis, gallstones, dehydration that can strain the kidneys, and low blood sugar alongside insulin or a sulfonylurea. Suspected side effects can be reported via the MHRA Yellow Card scheme. The differences follow from the chemistry:

• Other medicines. Because CYP3A4 breaks orforglipron down, its SmPC caps the dose at 9 mg alongside strong inhibitors such as clarithromycin, advises against strong inducers such as rifampicin and St John's wort, and halves the simvastatin dose. Semaglutide's SmPC sets no such limits.
• Oral contraceptives. Orforglipron's licence advises a non-oral or added barrier method for 30 days after starting and after each dose increase; semaglutide's found no clinically relevant change in combined-pill exposure.
• Pulse. Orforglipron raised average pulse by 6.7 to 8.6 beats a minute at its peak during dose escalation, easing to 3.9 to 5.2 by week 72. Semaglutide's SmPCs report a smaller rise: about 3 beats a minute for the injection, 2 for the tablet.
• Eyes. Both labels mention a rare optic-nerve condition (NAION). Semaglutide's SmPC cites epidemiological studies in type 2 diabetes suggesting about one extra case per 10,000 person-years; orforglipron's lists NAION as reported with GLP-1 receptor agonists generally. All three carry the black triangle for additional monitoring.
• Before pregnancy. Neither is for use in pregnancy. Semaglutide's licence says stop at least two months before trying to conceive; orforglipron's, at least three weeks — the half-life difference made practical.

Semaglutide 2.4 mg also holds a UK licence to cut the risk of heart attack and stroke in people with established cardiovascular disease and obesity or overweight (the SELECT trial); orforglipron has no such indication. See our side effects page and Foundayo side effects.

Where each stands in the UK

Wegovy is MHRA-licensed and available on the NHS in England through specialist weight-management services under NICE guidance (TA875) for up to two years, with far wider private access; the tablet has been available privately since July 2026.

The MHRA authorised orforglipron on 10 August 2026 for weight management and type 2 diabetes; it reached UK private prescribers on 24 August 2026. It is not on the NHS: NICE is appraising it (ID6516), with guidance provisionally due on 27 January 2027; our UK availability page tracks it. Legitimate supply is through GPhC-registered pharmacies and CQC-regulated clinics after a prescriber's assessment. Private prices vary between regulated providers; we quote none and name no sellers.

Frequently asked questions

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• Foundayo dosage schedule