The short version
Semaglutide (Ozempic, Wegovy) activates the GLP-1 receptor. It is cheaper, has been on the market longer, and is now available as a once-daily tablet as well as a weekly injection.
Tirzepatide (Mounjaro, Zepbound) activates both the GLP-1 and GIP receptors. Trials show greater average weight loss, and it costs more nearly everywhere.
Neither is universally better. The right one depends on your response, your tolerance, your budget, and what your prescriber thinks fits your history.
How They Work
GLP-1 is a hormone your gut releases after you eat. It tells your pancreas to release insulin, slows how quickly your stomach empties, and signals the parts of your brain that register fullness. Semaglutide mimics that hormone, which is why it reduces appetite and slows digestion.
Tirzepatide does the same thing at the GLP-1 receptor, and also activates the GIP receptor — another gut hormone involved in insulin release and fat metabolism. That is what “dual agonist” means. The working theory is that hitting two pathways produces a larger effect than hitting one, and the trial results are consistent with that.
What neither drug does is change your body permanently. Research consistently shows that most people regain weight after stopping, which is why these are generally framed as long-term treatments for a chronic condition rather than a course you finish. That reality should factor into your cost calculation more than it usually does.
What the Trials Found
| Medication | Trial average weight loss | Duration | Dosing |
|---|---|---|---|
| Semaglutide 2.4mg (Wegovy) | ~14.9% vs 2.4% placebo (STEP 1) | 68 weeks | Weekly injection |
| Oral semaglutide 25mg (Wegovy pill) | ~13.6% vs 2.2% placebo (OASIS 4) | 64 weeks | Once-daily tablet |
| Tirzepatide (Zepbound) | ~15–21% depending on dose (SURMOUNT) | 72 weeks | Weekly injection |
| Orforglipron (Foundayo) | Lilly reports ~11% (up to 25 lb) at 17.2mg | Per FDA approval trials | Once-daily tablet |
How to read these numbers
These are averages from trial populations who received structured lifestyle support alongside medication. The spread around each average is enormous — some participants lost well over 25% of their body weight, others lost almost nothing.
A 6-point difference in trial averages does not mean you will lose 6% more on tirzepatide. It means the population did, on average, under trial conditions. Your response to one drug tells you very little about your response to the other until you try it.
Side Effects
The profiles are similar because the mechanisms overlap. Gastrointestinal effects dominate both, and both tend to improve after the first four to six weeks as your body adjusts.
- Nausea — the most commonly reported effect for both, usually worst in the first weeks and after each dose increase.
- Constipation or diarrhea — common with both; tirzepatide users frequently report diarrhea specifically.
- Vomiting — less common, and usually tied to dose increases or eating past fullness.
- Fatigue — reported with both, often early in treatment.
- Injection-site reactions — mild and usually short-lived.
Less common but serious risks apply to both classes: pancreatitis, gallbladder problems (rapid weight loss raises gallstone risk regardless of the drug), and a thyroid tumor signal seen in rodent studies that carries a boxed warning. Both are contraindicated for people with a personal or family history of medullary thyroid carcinoma or MEN2.
Our side effects guide covers management in more detail, and we have specific articles on Wegovy and diarrhea and sulfur burps on Mounjaro.
Cost in 2026
Semaglutide is cheaper at essentially every provider and through every channel. The gap is substantial enough that it belongs in the decision.
| Route | Semaglutide | Tirzepatide |
|---|---|---|
| Manufacturer direct | NovoCare: $149/mo pill, $199/mo pen | LillyDirect: $299–$699/mo by dose |
| Compounded (Mochi) | $99/mo + $79 membership | $199/mo + $79 membership |
| Compounded (Alloy) | from $70/mo + $99 care | from $100/mo + $99 care |
| Compounded (TrimRx) | from $199/mo | from $299/mo |
| CoreAge RX | $99/mo | $149/mo |
How People Actually Choose
Reasons people start with semaglutide
- It costs less through every channel, often by $100 or more a month.
- It has a longer real-world track record and more published data.
- An oral tablet option now exists for people who do not want injections.
- Insurance formularies are somewhat more likely to include Wegovy.
Reasons people choose tirzepatide
- Larger average weight loss in trials.
- Zepbound is also approved for obstructive sleep apnea in adults with obesity, which can matter for coverage.
- Some people who plateau on semaglutide respond better to the dual mechanism.
- Some tolerate one better than the other for reasons that are not well predicted in advance.
What this decision is not
It is not permanent. Switching between the two is common, and your prescriber can manage it — though it involves restarting titration rather than matching doses, since the drugs are not equivalent milligram for milligram.
It is also not entirely yours to make. Your clinician decides what to prescribe based on your history, and your insurance may decide what it will cover. Going in with a preference is reasonable; going in with a demand is not.
Frequently Asked Questions
Which is more effective, semaglutide or tirzepatide?
In clinical trials, tirzepatide produced greater average weight loss. Semaglutide 2.4mg (Wegovy) produced about 14.9% average body weight reduction over 68 weeks in the STEP 1 trial, while tirzepatide (Zepbound) produced roughly 15% to 21% depending on dose in the SURMOUNT trials. Averages are not predictions, though — individual response varies widely, and the more effective drug on paper is not automatically the better choice for you.
Does tirzepatide have worse side effects?
Both cause a similar profile of gastrointestinal side effects — nausea, constipation, diarrhea, and vomiting are the most common, and they typically ease after the first few weeks. Trials have not shown tirzepatide to be dramatically worse tolerated despite producing more weight loss. What matters most for tolerability is titration speed, which is why rushing dose increases is a common mistake.
Which one is cheaper?
Semaglutide, at essentially every provider. NovoCare publishes brand-name Wegovy at $149/month for the pill and $199/month for the pen; LillyDirect publishes Zepbound self-pay from $299/month rising to $699 at higher doses. Compounded pricing follows the same pattern — Mochi charges $99/month for semaglutide and $199/month for tirzepatide.
Can I switch from one to the other?
People do switch, usually because of side effects, cost, or a weight-loss plateau. It is a clinical decision that involves restarting titration rather than matching doses one to one, since the two drugs are not equivalent milligram for milligram. Your prescriber needs to manage the transition.
Related Reading
- Tirzepatide vs semaglutide cost — the money side in more depth
- Best semaglutide providers
- Best tirzepatide providers
- Do you qualify for a GLP-1?
Medical Disclaimer
We're not doctors, and this article is for education only — it isn't medical advice. GLP-1 medications are prescription-only and require evaluation by a licensed healthcare provider. Individual results vary widely, and only a clinician who knows your history can determine what is safe and appropriate for you. See our full medical disclaimer.
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Every provider we've researched, with published pricing, medication type, and what's actually included.
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