Quick overview
- Europe/Sweden: Both are approved; tirzepatide has an EU indication for weight management. Availability is improving but may still vary.
- Both are once-weekly injections that reduce appetite and increase satiety.
- Effect: Tirzepatide (Mounjaro) produces greater average weight loss than semaglutide (Wegovy).
- Cardiovascular protection: Semaglutide 2.4 mg has proven cardiovascular benefit in people with overweight/obesity and established cardiovascular disease (CVD) without diabetes. Tirzepatide’s outcome data are still pending.
- Side effects: Mostly gastrointestinal (nausea, diarrhea, constipation). Both carry risk of gallstones/gallbladder disease.
- Pregnancy & contraception: Wegovy should be stopped at least 2 months before planned pregnancy. Tirzepatide can reduce the effectiveness of oral contraceptives during dose escalation—backup contraception is recommended for 4 weeks after initiation and each dose increase.
How do they work?
- Wegovy (semaglutide): A GLP-1 receptor agonist → reduces appetite, slows gastric emptying, lowers energy intake.
- Mounjaro (tirzepatide): A dual GIP/GLP-1 receptor agonist → similar but often stronger effects on appetite suppression and weight loss.
Effectiveness – how much weight loss?
- Wegovy: STEP-1 trial (without diabetes) showed −14.9% average body weight at 68 weeks vs placebo. Long-term data show ~15% at 2 years; in SELECT (CV population), ~10% over 4 years.
- Mounjaro: SURMOUNT-1 showed ~15–21% weight loss at 72 weeks (dose dependent). In the SURMOUNT-5 head-to-head trial, tirzepatide was superior to semaglutide 2.4 mg (−20.2% vs −13.7% at 72 weeks).
Takeaway: Tirzepatide shows greater average weight loss than semaglutide.
Cardiovascular outcomes
- Semaglutide 2.4 mg (Wegovy): SELECT trial showed 20% lower risk of CV death, MI, or stroke compared to placebo in people with established CVD without diabetes (median follow-up ~3.8 years).
- Tirzepatide (Mounjaro): Large outcome trials are ongoing/recently reported; definitive CV benefits are not yet established at the same level as semaglutide.
Side effects and precautions
Common to both:
- Nausea, vomiting, diarrhea, constipation, abdominal pain (often worst during dose escalation).
- Gallbladder issues: gallstones, cholecystitis.
- Rare but serious: acute pancreatitis (seek care if severe abdominal pain).
- Delayed gastric emptying can affect absorption of some oral medications.
Specific notes:
- Wegovy: Stop ≥2 months before planned pregnancy. Watch for diabetic retinopathy worsening in patients with diabetes during rapid glucose lowering.
- Mounjaro: May reduce oral contraceptive effectiveness—use backup contraception as above.
Contraindications (both): Personal/family history of medullary thyroid carcinoma (MTC) or MEN2. Caution with prior pancreatitis.
Before surgery/anesthesia: GLP-1 drugs may delay gastric emptying—discuss with your medical team.
Dosing (weekly injections, titrated)
- Wegovy: 0.25 → 0.5 → 1.0 → 1.7 → 2.4 mg (over ~5 months).
- Mounjaro: 2.5 → 5 → 7.5 → 10 → 12.5 → 15 mg (increased every 4 weeks until tolerated/target dose).
Wegovy vs Mounjaro – choosing between them
Choose Mounjaro (tirzepatide) if:
- Your priority is maximal weight loss.
- You can manage gradual titration and have backup contraception if needed.
Choose Wegovy (semaglutide 2.4 mg) if:
- You have established cardiovascular disease without diabetes and want proven CV risk reduction.
- You are planning pregnancy soon (clear 2-month discontinuation window).
Both require caution if you have a history of gallstones or pancreatitis.
Practical tips for best results
- Titrate slowly – if side effects occur, pause before increasing the dose.
- Pair with diet & exercise (small, protein-rich meals; avoid large/fatty meals early on).
- Stay hydrated; prolonged vomiting/diarrhea can cause dehydration and kidney issues.
- Share your full medication list with your doctor (absorption may be affected).
- Contraception: Use backup during tirzepatide dose adjustments.
What’s coming next?
- Higher-dose and oral semaglutide versions are being studied (OASIS program shows promising weight-loss results with 50 mg oral semaglutide). Not yet standard of care.
Bottom line
- For maximum weight loss → Mounjaro (tirzepatide).
- For proven cardiovascular protection in CVD → Wegovy (semaglutide 2.4 mg).
Both require medical evaluation, monitoring, and an individualized plan.
This is general medical information, not personal medical advice. Always discuss your own health conditions, medications, and pregnancy plans with your doctor before starting treatment.
Sources (selection): NEJM STEP-1, NEJM SELECT, NEJM SURMOUNT-1, NEJM SURMOUNT-5, EMA/FDA product information, Swedish Medical Products Agency (Läkemedelsverket).
