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You can switch from semaglutide to tirzepatide, and clinicians handle the crossover routinely. But no validated conversion table exists between the two drugs, so you restart tirzepatide at a low dose and titrate up from there. Expect the first month to feel like a step back before the dose gets high enough to work.
Who switches, and why
The draw is the trial numbers. In STEP 1 (Wilding et al., NEJM 2021, n=1,961), people on brand-name semaglutide (Wegovy) 2.4 mg lost 14.9% of their weight on average by week 68. In SURMOUNT-1 (Jastreboff et al., NEJM 2022, n=2,539), people on brand-name tirzepatide (Zepbound) lost 15.0% at 5 mg, 19.5% at 10 mg, and 20.9% at 15 mg by week 72. These were separate trials in different populations, so treat the gap as a rough guide. At 5 mg, the two results were about the same. The gap shows up at the 10 and 15 mg doses.
Here’s the mechanism behind it. Both drugs act on the GLP-1 receptor, which slows gastric emptying (how fast your stomach empties) and quiets the appetite centers in your brain. Tirzepatide also acts on a second receptor, called GIP.
The typical person who switches has been on semaglutide 2.4 mg for months. Their weight loss has slowed, and they still have a lot of weight to lose. The catch is that no trial has tested whether people who plateau on semaglutide lose more after switching. The SURMOUNT numbers come from people starting brand-name tirzepatide (Zepbound) fresh, and none of them were switching. It’s a reasonable bet, but it isn’t proven.
One group should think twice. If you have established cardiovascular disease, brand-name semaglutide (Wegovy) has SELECT behind it (Lincoff et al., NEJM 2023, n=17,604), where it lowered major heart events by 20% in relative terms over more than three years. Tirzepatide’s matching heart trial in people without diabetes hasn’t reported yet. A different trial, SURPASS-CVOT (Nicholls et al., NEJM 2025), studied adults with type 2 diabetes and heart disease. Brand-name tirzepatide (Mounjaro) was about as good as another GLP-1, dulaglutide (Trulicity), at preventing heart attacks, strokes, and heart-related deaths, but it didn’t prove better. In August 2026, the FDA approved Mounjaro to lower that risk in adults with type 2 diabetes. If you don’t have diabetes, switching for now means giving up SELECT’s evidence. The full comparison is in our semaglutide vs tirzepatide comparison.
The switch dose: there is no conversion chart
Neither drug’s label covers switching, and no published study maps semaglutide doses onto tirzepatide doses. If someone gives you an exact match, like “2.4 mg semaglutide equals X mg tirzepatide,” they’re making up a precision the research doesn’t have.
In practice, clinicians start tirzepatide low, at the label’s starting dose of 2.5 mg weekly, and never at the top. There’s one hard rule: one drug at a time, never both. Taking two of these gut-hormone drugs together stacks up side effects, with no evidence it helps more.
Switching doesn’t change the safety screening either. Both drugs carry the same boxed warning for thyroid C-cell tumors seen in rodents, and you can’t take either one if you or a family member has had medullary thyroid carcinoma or MEN 2.
On the Zepbound label, everyone starts at 2.5 mg. That isn’t about earning a higher dose. Your tolerance to semaglutide doesn’t carry over cleanly to a drug that adds GIP activity. And the label doesn’t allow starting higher because of past GLP-1 use. You take 2.5 mg for four weeks and then follow the standard ladder.
Your clinician will tell you when to take your first tirzepatide dose. Don’t overlap the two drugs.
What surprises people is that the first weeks can feel like starting over. Semaglutide clears slowly, so for a short time you have both drugs in you, and then very little of either. Your appetite may loosen around week two or three before tirzepatide catches up. That’s just the crossover, and it doesn’t mean the switch failed.
The first month: expect a lull
Your appetite comes back a little. A 2.5 mg dose of tirzepatide is only a starting dose. It turns down your appetite less than the 2.4 mg of semaglutide you were on, so food noise often comes back for a few weeks. Your weight loss may stall, or tick up a little, until the tirzepatide dose climbs high enough to work. That’s the plan working as designed, and it doesn’t mean the new drug is failing.
Familiar side effects can come back. Both drugs slow gastric emptying, so nausea, reflux, and early fullness can return at each dose step, the same way they did when you started semaglutide. Smaller meals and slower eating help again.
The ramp-up takes months. Per the Zepbound label, tirzepatide steps up 2.5 mg every 4 weeks, which puts 10 mg about three months after a 2.5 mg start. And the SURMOUNT-1 results come from 72 weeks on the drug. The details for each dose are in our tirzepatide guide.
What the switch costs
At Zappy, compounded semaglutide and compounded tirzepatide are made by LegitScript-verified 503A US pharmacies. As compounded medicines, they are not FDA-approved. It’s cash-pay with no insurance needed, and you can use FSA or HSA funds. Current prices are on each treatment page.
Bring your numbers
If you’ve stalled on semaglutide, a good conversation starts with your numbers. Bring your current dose, how many months you’ve been on it, any side effects, and how fast you’ve lost weight over the last eight weeks. That lets a clinician tell whether you’ve hit the most this drug can do, or a dosing problem. Take the quiz, and a Zappy clinician will review your case within 24 hours, including whether switching is the right call at all.
