GLP-1 side effects and plateaus: what TikTok gets wrong

What did @catarina_ugc actually say?

She's reporting that after losing seven stone on tirzepatide (Mounjaro), switching to semaglutide (Wegovy), and then returning to Mounjaro, the medication feels like it has stopped working. "I am telling you it has not worked," she says. "I feel like I've literally taken nothing." She's eating more, her sweet cravings have returned, and she's questioning whether she made a mistake leaving Wegovy. She also mentions she's recently quit smoking, which she flags herself as a complicating factor.

This is a genuinely common experience people report when cycling between GLP-1 medications, and her confusion is understandable. But the reasons behind what she's feeling are more complicated than "Mounjaro stopped working."

Does the science back this up?

Partly. There is real evidence that GLP-1 receptor agonists can have reduced appetite-suppressing effects when restarted after a break, particularly in the short term. But the mechanism is not straightforward.

Tirzepatide (Mounjaro) works differently from semaglutide (Wegovy). It activates both GIP and GLP-1 receptors, while semaglutide only targets GLP-1 receptors. Research published by Jastreboff et al. (2022, New England Journal of Medicine) found tirzepatide produced greater average weight loss than semaglutide in head-to-head comparisons, but individual responses vary considerably. There is no published clinical data specifically examining what happens when patients cycle from semaglutide back to tirzepatide, which means a lot of what people experience is being interpreted through anecdote rather than controlled evidence.

Nicotine withdrawal is also a real factor here. Nicotine suppresses appetite through dopaminergic and adrenergic pathways. Quitting smoking reliably increases appetite and food cravings, often significantly in the first weeks. The combination of restarting a medication and quitting smoking simultaneously makes it genuinely hard to isolate what is causing her increased hunger.

What did they get wrong (or right)?

She got the lived experience right. The observation that restarting a GLP-1 after a switch can feel less effective is reported widely in patient communities and is plausible physiologically. Receptor sensitivity and adaptation are real phenomena, though they are not well-studied in the context of switching between tirzepatide and semaglutide specifically.

Where she goes wrong is assuming the medication has simply "not worked" after one injection. Tirzepatide takes time to reach steady-state plasma concentrations. A single dose does not replicate the suppression you feel after weeks of consistent dosing. The appetite-suppressing effect of GLP-1 medications is cumulative, not immediate.

She also underestimates what quitting smoking is doing to her hunger. This is not a minor variable. Studies including Aubin et al. (2012, BMJ) found that people who quit smoking gain an average of 4-5 kg in the year following cessation, largely driven by increased caloric intake. Blaming the medication entirely while simultaneously withdrawing from nicotine is not a fair test of whether Mounjaro is working.

What should you actually know?

If you are switching between GLP-1 medications or restarting after a break, a few things are worth understanding clearly.

• One injection is not a clinical test. GLP-1 receptor agonists require several weeks of consistent dosing to produce meaningful appetite suppression. Judging efficacy after a single jab is not how these drugs work.
• Nicotine withdrawal and GLP-1 suppression are competing forces. If you quit smoking while starting or restarting a GLP-1 medication, expect the first few weeks to feel harder than they did before. That does not mean the medication is failing.
• Individual responses to tirzepatide and semaglutide genuinely differ. Some people respond better to one than the other. This is not well-predicted by prior response to the other medication, based on current evidence.
• Cravings for sweet foods after quitting smoking are well-documented and are not a sign of personal weakness. They are a pharmacological response to nicotine absence.

Her question, "did I do the right thing," is one for her prescribing clinician, not TikTok. Dose adjustments and medication switches should not be driven by how someone feels in week one.