Switching between GLP-1 medications
Where the label starts you on the new medication, and why no equipotency conversion between these drugs exists.
Read this first. There is no published equipotency between semaglutide, tirzepatide and liraglutide. No conversion table exists because the trials that would produce one have not been run. What this page shows is where the label starts each drug, and what prescribers commonly do when someone moves across. It is not a dose recommendation and it is not a substitute for the conversation with the person writing your prescription.
The dose you are on now, not the one you are aiming for.
The titration path from there
These are the label's steps. Prescribers hold people longer at a step all the time, usually for tolerability. Moving faster than this is what produces the nausea stories.
Why there is no conversion table
People expect a chart that says 1 mg of semaglutide equals some number of milligrams of tirzepatide. That chart does not exist, and the reason is not laziness.
Semaglutide is a GLP-1 receptor agonist. Tirzepatide acts on GLP-1 and GIP receptors. They are not the same drug at different strengths, they are different mechanisms with different side effect profiles and different tolerability curves in the same person. A dose you tolerate well on one can be miserable on the other, in either direction.
Head-to-head trials measured outcomes, not dose equivalence. Nobody has run the study that would let anyone publish a conversion, so anyone who hands you one made it up.
What prescribers actually do
The common case: restart at the bottom
Most prescribers restart the new drug at its label starting dose and titrate up from there, regardless of where you were on the old one. It is slower and it is frustrating if you were already at a high dose, but it is the approach with the safety data behind it.
The faster case: start one step up
Some prescribers will begin a step above the lowest for someone who was tolerating a high dose of the previous drug with no significant gastrointestinal effects. This is a clinical judgement about your specific history. It is not something to decide from a web page, and it is not something a compounding pharmacy can decide for you either.
Either way, the gap matters
If several weeks passed between the last dose of the old drug and the first of the new one, the tolerance you built is gone. Prescribers generally treat a long gap as starting fresh.
What changes when you switch
Your injection day can move
Both weekly drugs are once a week on any day you pick, so a switch is a natural moment to move to a day that suits you better. Moving to Saxenda means moving to daily injections, which is a bigger change in routine than people expect.
Your supply math changes
Different concentrations, different pen sizes, different refill intervals. Recalculate what you need with the supply calculator before you run out mid-switch.
Side effects can reset
The nausea that faded on your old medication may return at the start of the new one, because the adaptation is drug-specific. This is expected and usually temporary.
Common questions
- I am on 2.4 mg Wegovy. What Zepbound dose is that?
- There is no equivalent. The Zepbound label starts everyone at 2.5 mg weekly. Some prescribers begin at 5 mg for someone who tolerated a high semaglutide dose well, but that is a judgement about you, not a conversion of the number.
- Do I have to re-titrate from the beginning?
- Usually yes. The tolerance you built is largely specific to the drug you built it on, particularly moving between semaglutide and tirzepatide, which act on different receptors.
- How long should I wait between the last old dose and the first new one?
- For two weekly medications, prescribers commonly start the new one on the day the next old dose would have been due, so one week. That is a question for your prescriber, not a rule you can read off a page.
- Is switching because of a shortage different?
- The dosing considerations are identical. The practical difference is that shortage switches often happen with little notice, which is exactly when people are tempted to guess at a conversion. Do not.
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