A patient once told me she had been taken off Ozempic and put on Wegovy, and wanted to know whether the new drug would be stronger.
It is the same molecule. What changed was the sentence on the box, and with it who was willing to pay.
What was actually engineered
Your own GLP-1 is released from the gut after eating and is destroyed within a minute or two by an enzyme called DPP-4. That is fine for a signal meant to say “food has arrived” and useless as a drug.
Three modifications turned it into one. The peptide backbone was altered at the site DPP-4 attacks, so the enzyme can no longer cleave it. A long fatty acid chain was attached, which binds reversibly to albumin — the most abundant protein in blood — so the molecule circulates bound and is released slowly. And a spacer was added to hold the two parts in the right relationship.
The result is a half-life of roughly seven days rather than ninety seconds. That single number is the whole product: it is why the injection is weekly, why levels take four to five weeks to stabilise after each change, and why it must be stopped two months before a planned pregnancy.
It is also the reason no supplement can imitate it, which is examined in the “natural Ozempic” question.
~90 seconds
Half-life of your own GLP-1 — what the engineering had to overcome
3 brands
Ozempic, Wegovy and Rybelsus — one active ingredient between them
Albumin
The blood protein the fatty-acid chain binds to, creating the slow-release depot
The three brands
| Brand | Route | Licensed for | Maximum dose |
|---|---|---|---|
| Ozempic | Weekly injection | Type 2 diabetes; CV risk in T2D | 2.0 mg |
| Wegovy | Weekly injection | Weight management; CV risk in obesity | 2.4 mg |
| Rybelsus | Daily tablet | Type 2 diabetes | 14 mg |
Ozempic is the diabetes product and the one whose name escaped into general usage. Prescribing it for weight alone is off-label, which gives insurers a straightforward basis for refusal.
Wegovy is the weight-management licence, and since 2024 also carries a cardiovascular risk reduction indication — a change that mattered more for access than any clinical argument about obesity ever has. The reasoning is in the SELECT trial and the label change.
Rybelsus is oral, taken daily on an empty stomach with a small sip of water and nothing else for thirty minutes, because absorption is poor and fussy. A higher-dose oral formulation for obesity is a separate development — see the obesity pill.
The head-to-head between the two injectables is in Ozempic versus Wegovy, and the eligibility thresholds in do you qualify.
What it does in the body
Four mechanisms, only one of which is about the pancreas.
Glucose-dependent insulin release. It stimulates insulin only when glucose is elevated, which is why semaglutide alone rarely causes hypoglycaemia. Combined with insulin or a sulfonylurea, that protection disappears — see drug interactions.
Suppressed glucagon. Less glucose released from the liver.
Slowed gastric emptying. The source of the fullness, and of nearly every gastrointestinal side effect: nausea, reflux, constipation and the anaesthetic precautions.
Central action on appetite. Receptors in the hypothalamus and brainstem, which is where the reduction in food noise comes from.
The fuller mechanism is in how GLP-1 drugs work.
The expanding licence
This is the part that has changed fastest, and it is worth tracking because indications drive coverage.
- Type 2 diabetes — the original approval
- Cardiovascular risk reduction in type 2 diabetes, on the strength of SUSTAIN-6
- Chronic weight management — Wegovy, 2021
- Cardiovascular risk reduction in obesity without diabetes — 2024, from SELECT
- Chronic kidney disease in type 2 diabetes — from the FLOW result, covered in the kidney indication
- Metabolic dysfunction-associated steatohepatitis — see the liver approval
Each of these is a separate route past a formulary exclusion, which is why the question “what are you taking it for” is frequently the most consequential one in the appointment. See appealing a prior authorisation.
Six licences, one molecule. The chemistry stopped changing in 2015; everything since has been argument about what it is allowed to be for.
Getting hold of it
Through insurance, where the indication you apply under does most of the work — what it costs.
Self-pay through the manufacturer. Novo Nordisk sells directly through its NovoCare pharmacy channel at prices far below list — see cash-pay and direct pricing.
Through a telehealth platform. Hims & Hers and similar services now write a large share of American prescriptions, with the caveats in the telehealth business.
Compounded, which is a genuinely different risk proposition — choosing a compounding pharmacy.
Abroad, where generic semaglutide is now available in several markets — generics outside the US.
The practical summary
One molecule, engineered once, sold under three names, licensed for six things and counting.
If you are trying to work out which product you should be on, the question is almost never chemical. It is which indication you meet and which box your plan will pay for — and those are answerable in an afternoon. Start with do you qualify and the dose charts.