Semaglutide vs Tirzepatide: Which GLP-1 is Right for You?
The Quick Answer
Both semaglutide and tirzepatide are GLP-1 receptor agonists used for weight loss. Tirzepatide (Mounjaro, Zepbound) is dual-action (GLP-1 + GIP), typically produces 15-20% weight loss vs semaglutide's 10-15%, but costs more and may have higher initial nausea rates. Semaglutide (Ozempic, Wegovy) is well-studied, slightly gentler for GI-sensitive patients, and costs less.
Bottom line: Tirzepatide wins on efficacy if you can tolerate it. Semaglutide wins on cost and tolerability for first-time GLP-1 users.
Mechanism: How They Work
Semaglutide
Semaglutide is a GLP-1 receptor agonist. It mimics glucagon-like peptide-1, a gut hormone that:
- Slows gastric emptying (you feel full longer)
- Reduces appetite via central nervous system pathways
- Improves insulin sensitivity
- Lowers blood sugar (approved for Type 2 diabetes)
FDA-approved as Ozempic (diabetes) and Wegovy (weight loss). Flow prescribes compounded semaglutide — same active ingredient, lower cost, no insurance required.
Tirzepatide
Tirzepatide is a dual agonist — it activates both GLP-1 and GIP (glucose-dependent insulinotropic polypeptide) receptors. The GIP component enhances insulin secretion and may improve fat metabolism beyond GLP-1 alone.
FDA-approved as Mounjaro (diabetes) and Zepbound (weight loss). Flow prescribes compounded tirzepatide.
Efficacy: Weight Loss Results
| Metric | Semaglutide | Tirzepatide |
|---|---|---|
| Average weight loss (12 weeks) | 10-15% of body weight | 15-20% of body weight |
| Clinical trial data | STEP trials (2+ years) | SURMOUNT trials (18 months) |
| Plateau timing | Week 16-20 | Week 20-24 |
Real-world context: A 200 lb patient on semaglutide might lose 20-30 lbs in 12 weeks. On tirzepatide, 30-40 lbs. Individual response varies — some patients respond better to one than the other.
Side Effects
Both peptides share common GI side effects (most resolve after titration):
- Nausea (30-40% of users, usually mild)
- Constipation or diarrhea
- Fatigue during first 2 weeks
- Injection site reactions
Key difference: Tirzepatide's dual mechanism may cause slightly more nausea in the first 4 weeks. Slower titration helps. Semaglutide is generally gentler for GI-sensitive patients.
Rare but serious risks (both peptides): pancreatitis, gallbladder issues, thyroid tumors (animal studies only). Flow's NP screens for contraindications before prescribing.
Cost Comparison
| Option | Semaglutide | Tirzepatide |
|---|---|---|
| Flow compounded (12 weeks) | $500 | $600 |
| Brand name (out-of-pocket) | $900-$1,300/month | $1,000-$1,400/month |
Flow pricing includes the medication, injection supplies, and 12 weeks of NP supervision. No hidden fees.
Who Should Choose Semaglutide?
- First-time GLP-1 users (gentler titration)
- Patients with sensitive GI systems
- Lower budget (saves $100 vs tirzepatide)
- 10-15% weight loss goal is sufficient
Who Should Choose Tirzepatide?
- Patients seeking maximum weight loss (15-20%)
- Prior semaglutide users who plateaued
- Willing to tolerate higher nausea risk for better results
- Metabolic syndrome or pre-diabetes (dual GLP-1/GIP action)
Can You Switch Between Them?
Yes. Many Flow patients start on semaglutide and switch to tirzepatide if they plateau or want faster results. The reverse (tirzepatide → semaglutide) is less common but possible if cost or side effects are issues.
Switching requires a 1-week washout and re-titration. Your NP will guide timing.
Next Steps
Not sure which peptide fits your goals? Take our 2-minute quiz for a personalized recommendation. Or book a free 15-minute consult with our NP to discuss your medical history and weight loss timeline.
Flow programs: Semaglutide ($500/12 weeks) · Tirzepatide ($600/12 weeks) · All programs →