Switching from semaglutide to tirzepatide

The question everyone arrives with is "I'm on 2.4 mg — what's the equivalent?" There isn't one. Here's why, and what happens instead.

There is no conversion

Semaglutide works on one receptor. Tirzepatide works on two — GLP-1 and GIP. They are different molecules with different potency curves, and no regulator, manufacturer or trial has published a dose equivalence between them. Any chart claiming 2.4 mg semaglutide = X mg tirzepatide was made up by whoever published it.

So the honest answer to "what dose do I start at" is: 2.5 mg, the same as someone who's never taken either.

Why you go back to the bottom of the ladder

It feels wrong. You've spent four months building up tolerance, you're managing the nausea fine, and now you're being told to start again at the beginning.

The reason is that the tolerance you built is to semaglutide. Tirzepatide's second receptor does things to your gut that your body hasn't met yet. People who jump straight to what feels like an equivalent dose are the ones who lose a fortnight.

Some prescribers will start someone at 5 mg if they were at the top of the semaglutide ladder and tolerating it comfortably. That's a judgement call, made by someone who knows your history, and it is not the default.

When to take the first one

Usually on the day your next semaglutide dose would have been due — a week after the last one. No washout, no gap. Semaglutide has a long half-life and clears over several weeks anyway, so there's overlap regardless; that's expected, not a problem. Your prescriber may say otherwise for their own reasons, and they win.

The part this site is actually for: your units change completely

New drug, new vial, new concentration, new number. The instinct to keep drawing the same mark on the barrel is the single most dangerous habit in the switch.

Eight times the milligrams from an identical-looking draw. That's the whole warning. Work it out again from the new label, every time.

What to expect in the first month

• Appetite suppression may dip before it climbs. 2.5 mg of tirzepatide is a starting dose, not a working one — it can feel weaker than the semaglutide you left. That's the ladder, not the drug failing.
• The side effects can feel different rather than worse. Different receptor, different profile.
• Weight can stall for a few weeks. Common during the restart, and not a sign the switch was a mistake.

Four weeks at 2.5, then the normal schedule on the tirzepatide chart.