Medically Reviewed Content
Written by Rob Anderson, Health Technology Researcher & Medical Content Specialist. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting any medication.
The GLP-1 medication space now has two dominant players: semaglutide (Ozempic/Wegovy/compounded) and tirzepatide (Mounjaro/Zepbound). Both produce remarkable weight loss. This guide cuts through the hype and gives you the honest comparison across every dimension that matters.
The Key Difference: Mechanism
Semaglutide is a GLP-1 receptor agonist — it mimics the GLP-1 gut hormone to suppress appetite, slow gastric emptying, and improve insulin sensitivity. Tirzepatide is a dual GIP/GLP-1 receptor agonist — it activates both GLP-1 and GIP (glucose-dependent insulinotropic polypeptide) receptors simultaneously. The GIP component appears to amplify the metabolic effects of GLP-1 activation, producing greater fat mobilisation and potentially less nausea than semaglutide at equivalent effective doses.
Weight Loss Comparison
The headline numbers: the STEP trials showed semaglutide 2.4mg produces average weight loss of 14.9–17.3% of body weight over 68 weeks. The SURMOUNT trials showed tirzepatide 15mg produces average weight loss of 20.9–22.5% over 72 weeks — a meaningful gap of approximately 5–7 percentage points in favour of tirzepatide. That translates to roughly 8–12 extra pounds lost on average for a 200lb person.
However: these are averages with wide distributions. Some people lose 25%+ of body weight on semaglutide. Some people respond better to semaglutide than tirzepatide. There are no reliable predictors of individual response.
Cost Comparison (2026)
| Medication | Brand Cost/month | Compounded Cost/month |
|---|---|---|
| Semaglutide (Ozempic/Wegovy) | $900–$1,350 | $149–$350 |
| Tirzepatide (Mounjaro/Zepbound) | $1,000–$1,400 | $250–$500 |
Compounded semaglutide is substantially cheaper than compounded tirzepatide and dramatically cheaper than brand tirzepatide. For cost-constrained patients, this difference is clinically relevant — adherence to a $200/month medication beats non-adherence to a $1,200/month one every time.
Side Effect Profile
Both medications share similar GI side effects: nausea, diarrhoea, vomiting, constipation. Clinical trial data suggests tirzepatide may produce slightly less nausea than semaglutide at therapeutically equivalent effective doses — possibly due to the GIP component moderating GLP-1 receptor effects in the gut. However GI side effects at equivalent titration schedules are broadly comparable in real-world use.
Cardiovascular Evidence
Semaglutide has the superior cardiovascular evidence base. The SELECT trial (2023) demonstrated a 20% reduction in MACE events in patients with obesity and established CV disease — a landmark result. Tirzepatide’s cardiovascular outcome trial (SURPASS-CVOT) is underway but results are not yet published. For patients with established heart disease, semaglutide’s proven CV benefit gives it a meaningful evidence advantage in 2026.
Which Should You Choose?
Consider semaglutide if: you want the lowest cost option, you have established cardiovascular disease (proven CV benefit), or you prefer a medication with more long-term safety data. Consider tirzepatide if: maximum weight loss is the priority and cost is less of a constraint, or if you have not responded adequately to semaglutide. Either way, the decision should be made with your physician based on your full clinical picture.
Frequently Asked Questions
Q: Is Mounjaro better than Ozempic for weight loss?
A: The clinical trial data suggests tirzepatide (Mounjaro/Zepbound) produces greater average weight loss than semaglutide (Ozempic/Wegovy) — approximately 20–22% vs 15% of body weight at maximum doses. However, direct head-to-head trials are limited, individual responses vary significantly, compounded semaglutide is substantially cheaper than brand tirzepatide, and both produce clinically meaningful results. Mounjaro is not definitively better for every person — it depends on individual response, cost, availability, and medical history.
Q: What is the difference between Ozempic and Mounjaro?
A: Ozempic/Wegovy contains semaglutide, a GLP-1 receptor agonist. Mounjaro/Zepbound contains tirzepatide, a dual GIP/GLP-1 receptor agonist — it activates both the glucose-dependent insulinotropic polypeptide (GIP) receptor and the GLP-1 receptor simultaneously. This dual action is believed to produce greater weight loss and metabolic benefit than GLP-1 agonism alone. Both are once-weekly subcutaneous injections. Mounjaro is currently approved for type 2 diabetes; Zepbound for obesity specifically.
Q: Can I switch from Ozempic to Mounjaro?
A: Yes, switching is clinically possible and some people do move from semaglutide to tirzepatide, particularly if they have plateaued or if weight loss goals haven’t been met. The transition requires physician oversight — there is no direct dose equivalence and your doctor will typically start tirzepatide at the lowest dose regardless of your semaglutide dose, then titrate up. Switching should be a considered medical decision, not a first response to a plateau.
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