Tirzepatide produces more weight loss. Semaglutide has more long-term safety data.
That's the one-sentence answer. Mounjaro/Zepbound (tirzepatide) delivers roughly 21-27% body weight loss in trials vs. 15-17% for Ozempic/Wegovy (semaglutide). But semaglutide has been on the market since 2017, giving it 9 years of real-world safety surveillance. Tirzepatide launched in 2022 and has 4 years.
Both work. The right choice depends on your diagnosis, insurance coverage, and tolerance for GI side effects.
TL;DR
- Tirzepatide (Mounjaro/Zepbound): 21-27% weight loss, dual GIP/GLP-1 mechanism, fewer years of real-world data
- Semaglutide (Ozempic/Wegovy): 15-17% weight loss, GLP-1 only, 9 years on market, proven cardiovascular benefit (SELECT trial)
- FAERS reports: 69,000 for semaglutide vs. 28,000 for tirzepatide (reflects prescribing volume, not relative safety)
- Cost: both $935-1,350/month at list price. Insurance coverage varies by diagnosis.
- Tirzepatide overtook semaglutide as the most-prescribed GLP-1 by December 2025
How we compared them
We pulled data from three sources:
- Published clinical trials: STEP 1-5 (semaglutide), SURMOUNT 1-4 (tirzepatide for obesity), SURPASS 1-5 (tirzepatide for diabetes), and SELECT (semaglutide cardiovascular outcomes)
- FDA FAERS database: Adverse event reports queried through the openFDA API for both molecules through Q2 2026
- CMS pricing files: NADAC and Part D spending data for current cost figures
No comparison article in the top 10 search results uses FAERS data. Most cite vague "studies suggest" language without naming specific trials. This post names every source.
Clinical trial results: head-to-head
Weight loss trials
| Trial | Drug | Dose | Duration | Mean Weight Loss | Participants |
|---|---|---|---|---|---|
| STEP 1 | Semaglutide | 2.4mg weekly | 68 weeks | 14.9% | 1,961 |
| STEP 2 | Semaglutide | 2.4mg weekly | 68 weeks | 9.6% (diabetes patients) | 1,210 |
| STEP 3 | Semaglutide | 2.4mg + behavioral therapy | 68 weeks | 16.0% | 611 |
| STEP 5 | Semaglutide | 2.4mg weekly | 104 weeks | 15.2% (2-year data) | 304 |
| SURMOUNT-1 | Tirzepatide | 5/10/15mg weekly | 72 weeks | 15.0% / 19.5% / 20.9% | 2,539 |
| SURMOUNT-2 | Tirzepatide | 10/15mg weekly | 72 weeks | 12.8% / 14.7% (diabetes) | 938 |
| SURMOUNT-3 | Tirzepatide | 10/15mg weekly | 84 weeks | 26.6% (with lifestyle intervention) | 579 |
At maximum doses, tirzepatide produces 5-10 percentage points more weight loss than semaglutide. The SURMOUNT-3 result (26.6%) is the highest weight loss number from any approved drug trial.
Important caveat: no published head-to-head trial directly compares tirzepatide 15mg to semaglutide 2.4mg. SURPASS-2 compared tirzepatide against semaglutide 1mg (the diabetes dose, not the 2.4mg weight-loss dose). Comparing across trials has limitations.
Diabetes (A1c reduction)
| Trial | Drug | Best Dose Result | A1c Reduction |
|---|---|---|---|
| SURPASS-1 | Tirzepatide 15mg | Monotherapy | -2.07% |
| SURPASS-2 | Tirzepatide 15mg vs. semaglutide 1mg | Head-to-head | -2.30% vs -1.86% |
| SURPASS-3 | Tirzepatide 15mg vs. insulin degludec | vs. insulin | -2.37% vs -1.34% |
| SUSTAIN-7 | Semaglutide 1mg vs. dulaglutide | Head-to-head | -1.8% vs -1.4% |
Tirzepatide wins on A1c reduction too. In the only direct comparison (SURPASS-2), tirzepatide 15mg beat semaglutide 1mg by 0.44 percentage points. That's clinically meaningful for diabetes control.
Cardiovascular outcomes
This is where semaglutide has the edge — for now.
The SELECT trial (12,000+ patients, 3.4 years follow-up) showed semaglutide 2.4mg reduced major adverse cardiovascular events (heart attack, stroke, cardiovascular death) by 20% compared to placebo in overweight/obese adults without diabetes.
Tirzepatide has no published cardiovascular outcomes trial yet. The SURPASS-CVOT trial is ongoing (expected completion ~2027). Until those results arrive, semaglutide is the only GLP-1 with proven cardiovascular benefit independent of diabetes or weight loss.
For patients with established cardiovascular disease or high cardiovascular risk, this distinction matters clinically.
FDA FAERS comparison: what 97,000 reports show
We queried the openFDA adverse events endpoint for both molecules. Here's what the database contains through Q2 2026:
| Metric | Semaglutide | Tirzepatide |
|---|---|---|
| Total FAERS reports | ~69,000 | ~28,000 |
| Serious reports (%) | 37% | 34% |
| Reports involving death | ~2,800 (4.1%) | ~900 (3.2%) |
| Reports per year on market | ~7,700/yr (9 years) | ~7,000/yr (4 years) |
The raw numbers favor semaglutide having "more" adverse events. But normalize by time on market, and the reporting rates are similar (~7,000-7,700 per year). This makes sense: both are prescribed to similar patient populations at similar rates now.
Top reported reactions compared
| Reaction | Semaglutide (% of reports) | Tirzepatide (% of reports) |
|---|---|---|
| Nausea | 18% | 20% |
| Vomiting | 10% | 12% |
| Diarrhea | 7% | 8% |
| Abdominal pain | 6% | 7% |
| Constipation | 4% | 5% |
| Headache | 5% | 4% |
| Pancreatitis | 3% | 2.5% |
| Gastroparesis | 2% | 1.5% |
| Hair loss (alopecia) | 2% | 3% |
| Injection site reaction | 2% | 4% |
The GI side effect profile is nearly identical. Two differences stand out:
Injection site reactions are higher for tirzepatide (4% vs 2%). This showed up in clinical trials too. The tirzepatide formulation appears to cause more local irritation.
Hair loss reports are slightly higher for tirzepatide (3% vs 2%). Likely because tirzepatide produces more rapid weight loss, and telogen effluvium (temporary hair shedding) correlates with rate of weight loss, not the specific drug.
The gastroparesis signal
Both drugs slow gastric emptying by design. FAERS gastroparesis reports:
- Semaglutide: ~1,400 reports (2% of total)
- Tirzepatide: ~420 reports (1.5% of total)
Semaglutide's higher absolute count reflects more years of exposure. The percentage is similar. Neither drug has a clearly worse gastroparesis profile based on FAERS data alone.
Cost comparison (August 2026)
| Product | Indication | List Price/Month | Typical Insured Copay |
|---|---|---|---|
| Ozempic (semaglutide 0.5-2mg) | Type 2 diabetes | ~$935 | $25-150 |
| Wegovy (semaglutide 2.4mg) | Weight management | ~$1,349 | $0-500 (often denied) |
| Mounjaro (tirzepatide 5-15mg) | Type 2 diabetes | ~$1,023 | $25-150 |
| Zepbound (tirzepatide 5-15mg) | Weight management | ~$1,059 | $0-500 (often denied) |
Key cost differences:
For diabetes patients: Both have strong insurance coverage. Copays are similar ($25-150/month with commercial insurance, $0 with manufacturer coupons for eligible patients).
For weight loss only: Coverage is the battleground. Many commercial plans cover Wegovy or Zepbound for obesity (BMI 30+ or 27+ with comorbidities). Medicare Part D covers diabetes indications but not weight loss for most enrollees. Self-pay runs $900-1,350/month.
Zepbound is cheaper than Wegovy at list price ($1,059 vs $1,349). Eli Lilly priced Zepbound below Wegovy deliberately to compete on cost. For cash-pay patients, this price difference matters over 12+ months of treatment.
IRA impact (2027): Medicare selected semaglutide for price negotiation (prices effective January 2027). Tirzepatide was not selected in the first two rounds. This means Medicare patients on Ozempic will see lower costs before Mounjaro patients do.
Which one is right for you?
This is not medical advice. But the data points toward different choices for different situations:
Tirzepatide (Mounjaro/Zepbound) may be better if:
- Maximum weight loss is the primary goal
- You don't have established cardiovascular disease
- Your insurance covers it (or you can afford list price)
- You tolerate injections well (slightly higher injection site reactions)
Semaglutide (Ozempic/Wegovy) may be better if:
- You have cardiovascular disease or high CV risk (SELECT trial evidence)
- You want the longest safety track record available
- You're a Medicare patient (IRA negotiated pricing coming 2027)
- You prefer a drug with 9 years of real-world post-market surveillance
Either drug works well if:
- Your primary diagnosis is type 2 diabetes (both achieve >2% A1c reduction)
- You need significant weight loss (both produce 15%+ at adequate doses)
- GI tolerance is a concern (similar side effect profiles)
Can you switch from Ozempic to Mounjaro?
Yes. Switching between GLP-1 drugs is common. The typical protocol:
- Stop Ozempic (semaglutide) after your last weekly dose
- Wait one week (the normal injection interval)
- Start Mounjaro (tirzepatide) at the lowest dose (2.5mg)
- Titrate up every 4 weeks as tolerated
Doctors restart at the lowest tirzepatide dose regardless of your semaglutide dose because the drugs have different receptor profiles. The titration period means 2-3 months before reaching full therapeutic dose on the new drug. Some weight regain during the transition is normal.
Going the other direction (Mounjaro to Ozempic) follows the same pattern: stop, wait one week, start semaglutide 0.25mg, titrate up monthly.
What about generics?
| Drug | Patent Expiration | Generic Expected |
|---|---|---|
| Semaglutide (Ozempic/Wegovy) | 2026-2027 (core patents) | Late 2027 or 2028 |
| Tirzepatide (Mounjaro/Zepbound) | 2036+ (later filing) | Not before 2036 |
Semaglutide generics could reach market within 1-2 years. Tirzepatide's patents run a decade longer. If long-term cost matters, semaglutide will become dramatically cheaper first.
Generic semaglutide prices will likely drop 70-90% from current list prices, following typical biologic/biosimilar pricing patterns. That would put monthly costs in the $100-300 range.
FAQ
Is Mounjaro better than Ozempic for weight loss? In clinical trials, yes. Tirzepatide (Mounjaro/Zepbound) produces 21-27% weight loss vs. 15-17% for semaglutide (Ozempic/Wegovy) at maximum doses. No head-to-head trial at equal weight-loss doses exists, but the evidence consistently favors tirzepatide.
Is Ozempic safer than Mounjaro? Their side effect profiles are nearly identical in FAERS data. Semaglutide has more years of post-market surveillance (9 years vs. 4), which gives more confidence about rare, long-term risks. Neither has a clearly better safety profile based on available data.
How much do Ozempic and Mounjaro cost per month? List prices: Ozempic ~$935, Mounjaro ~$1,023. For weight loss: Wegovy ~$1,349, Zepbound ~$1,059. With insurance covering diabetes, copays run $25-150. Weight loss coverage varies widely by plan.
Can I switch from Ozempic to Mounjaro? Yes. Wait one week after your last Ozempic dose, then start Mounjaro at 2.5mg (the lowest dose) regardless of your previous semaglutide dose. Titrate up every 4 weeks. Expect 2-3 months to reach therapeutic dose.
Which has worse side effects? Both cause similar GI side effects (nausea, vomiting, diarrhea) at similar rates. Tirzepatide has slightly more injection site reactions (4% vs 2% of FAERS reports). Both can cause hair loss during rapid weight loss.
Does insurance cover both? For type 2 diabetes: yes, most plans cover both. For weight loss only: coverage varies by plan and depends on BMI and comorbidities. Many commercial plans now cover Wegovy or Zepbound for obesity. Medicare coverage for weight loss remains limited.
Will generic Ozempic be available soon? Semaglutide patents expire 2026-2027. Generic/biosimilar versions could reach market by late 2027 or 2028. Tirzepatide patents extend to ~2036, so no generic Mounjaro for a decade.
Which is better for diabetes specifically? Tirzepatide produced greater A1c reduction in the SURPASS-2 head-to-head trial (2.30% vs 1.86%). Both are highly effective. Choice often depends on insurance formulary placement and cardiovascular risk profile.
Does either have proven heart benefits? Semaglutide 2.4mg reduced cardiovascular events by 20% in the SELECT trial (12,000+ patients, 3.4 years). Tirzepatide's cardiovascular outcomes trial (SURPASS-CVOT) is ongoing, with results expected ~2027.
How fast do you lose weight on each? Both show significant weight loss by week 12 (roughly 5-8%). Maximum effect is reached around week 60-72 in most trials. Tirzepatide reaches higher maximum weight loss but follows a similar trajectory.
Clinical trial data from published STEP, SURMOUNT, SURPASS, and SELECT trial results. FAERS data queried from openFDA drug adverse events endpoint through Q2 2026. Pricing from CMS NADAC files and manufacturer published list prices. Last verified August 2026.
Want this data via API? The MyfitByte API provides structured access to FAERS adverse event comparisons, drug pricing, and prescribing volume data. See our Ozempic side effects analysis and GLP-1 prescribing trends for related data.
Published on 2026-08-24 · 10 min read
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