Common and legitimate reasons:
- Side effects that have not settled at a given dose
- Inadequate response after a fair trial
- Supply problems with the current medicine
- Cost, particularly as the dose ladder climbs
- A preference for a tablet over an injection, now that oral options exist
All of these are worth discussing. What they are not is a reason to arrange the switch yourself.
Doses Do Not Map Across
This is the central point. The strengths of these medicines are not comparable numbers.
- Semaglutide runs 0.25mg to 2.4mg weekly, and up to 7.2mg for the higher-dose licence
- Tirzepatide runs 2.5mg to 15mg weekly
- Oral semaglutide for weight management runs 1.5mg, 4mg, 9mg and 25mg daily
A person on 10mg of tirzepatide is not "on more" than someone on 2.4mg of semaglutide. They are different molecules with different potencies and, in tirzepatide's case, a different mechanism — it acts on GIP as well as GLP-1 receptors.
Guessing at an equivalent dose is how people end up either with severe nausea or with weeks of ineffective treatment.
How a Switch Is Usually Handled
Approaches vary by medicine and by prescriber, but the general shape:
- Timing matters. Weekly injections stay in the system for days. A switch is usually timed around when the next dose would have fallen.
- You may not restart at the bottom. Someone who has tolerated a substantial dose of one GLP-1 does not always need the full slow climb on another — but this is a clinical judgement, not a default.
- Oral semaglutide has its own rule. Patients on 2.4mg weekly injections can transition to 25mg tablets daily, which is a specific mapping rather than a general principle.
- Expect side effects to reset somewhat. Even a well-judged switch often brings a period of nausea while your body adjusts.
The Absorption Rules Change Too
Switching from an injection to oral semaglutide means adopting a daily routine with strict timing — an empty stomach, and a wait before eating or drinking. People who breeze through the clinical side of a switch often come unstuck here, because the medicine is only as good as its absorption.
Switching Pharmacy Is a Different Thing
Moving supplier while staying on the same medicine and dose is much simpler — you need a new prescription and continuity of supply. Plan the overlap so you do not run out during the transfer, and confirm the new provider has your strength in stock before cancelling anything.
This is often the switch that actually saves money, particularly if your current provider prices per strength and you are climbing the ladder.
What to Tell a New Prescriber
- Exactly which medicine and dose you are on, and for how long
- The full escalation history — what you tolerated and what you did not
- Any side effects, including ones you decided to live with
- Why you want to change
A prescriber who does not ask for that history before switching you is not doing the assessment properly, and the GPhC's guidance on high-risk medicines exists precisely to make that assessment happen.