Tirzepatide vs semaglutide: which produces more weight loss?

The Head-to-Head Data

SURMOUNT-5, published 2025, is the only randomized direct comparison of tirzepatide and semaglutide at max approved doses for obesity. Over 72 weeks:

• Tirzepatide 15 mg/week: 20.2% mean body weight loss
• Semaglutide 2.4 mg/week: 13.7% mean body weight loss
• Difference: 6.5 percentage points in favor of tirzepatide

For a 250-pound person, that's roughly 51 lbs on tirzepatide vs 34 lbs on semaglutide.

Why Tirzepatide Wins on Efficacy

Tirzepatide is a dual agonist — it activates both GLP-1 and GIP receptors. Semaglutide only activates GLP-1. The additional GIP agonism contributes to:

• Greater fat-specific weight loss (some evidence of improved body composition outcomes)
• Slightly better glycemic control in diabetic populations
• Possibly better insulin sensitization

The dual mechanism is why tirzepatide is sometimes called a "GIP/GLP-1" rather than just a GLP-1.

Side Effect Comparison

Side effect profiles are broadly similar — GI dominant, mostly dose-related:

• Nausea: Tirzepatide ~24%, Semaglutide ~20% at max dose
• Diarrhea: Tirzepatide ~19%, Semaglutide ~16%
• Constipation: Tirzepatide ~11%, Semaglutide ~10%
• Vomiting: Tirzepatide ~10%, Semaglutide ~10%
• Sulfur burps: Tirzepatide users report this more frequently — a quality-of-life issue the trial didn't capture cleanly

Tirzepatide side effects are modestly more common but rarely severe enough to differentiate decisively.

Cost Comparison (April 2026)

• Brand Zepbound (tirzepatide) cash price: ~$1,060/month list, ~$399 with manufacturer direct program
• Brand Wegovy (semaglutide) cash price: ~$1,350/month list, ~$499 with manufacturer programs
• Compounded tirzepatide: $200–$500/month
• Compounded semaglutide: $150–$400/month

Tirzepatide brand is modestly cheaper. Compounded tirzepatide is modestly more expensive. Net: similar out-of-pocket in most markets.

Insurance Coverage

Coverage has expanded for both, but semaglutide (Wegovy) has longer time in market and broader formulary placement. Tirzepatide (Zepbound) coverage is now common but slightly less universal. Check your specific plan.

Which to Start With

Reasonable decision framework:

Start with tirzepatide if:

• BMI > 35 or need to lose > 15% body weight
• Type 2 diabetes (slight edge on A1c lowering)
• Previous semaglutide trial with inadequate response
• Cost is equivalent through your path

Start with semaglutide if:

• BMI 27–32 with moderate weight loss goal
• Longer safety record matters to you (semaglutide has been on the market longer)
• Cardiovascular disease — semaglutide has specific CVD risk reduction indication (SELECT trial)
• Insurance covers semaglutide but not tirzepatide
• You've had prior GI issues with meds and want the slightly milder option

Switching From One to the Other

Common scenarios:

Semaglutide → Tirzepatide

Plateau on semaglutide 2.4 mg for 3+ months → switch to tirzepatide. Start tirzepatide at 2.5 mg (standard starting dose, not matched to semaglutide exposure) and titrate. Expect 1–2 weeks of GI readjustment as the GIP agonism kicks in.

Tirzepatide → Semaglutide

Less common. Usually driven by cost or insurance, or by inability to tolerate tirzepatide's GI effects. Start semaglutide at 0.25 mg and titrate normally.

Can You Use Both?

No. Both are GLP-1 receptor agonists (tirzepatide is partially); stacking them provides no additional benefit and dramatically increases side effects. Some compounded providers have marketed "combination peptide" formulations; this is not evidence-based.

Pregnancy and Fertility

Neither is recommended during pregnancy or active attempts to conceive. Both require 8 weeks off before planned conception. Both have similar recommendations.

Bottom Line

Tirzepatide has the efficacy edge. Semaglutide has the longer safety record and slightly better tolerability. For most patients, tirzepatide is now the default first-line for meaningful weight loss (BMI > 32), and semaglutide is the default for milder indications or specific cardiovascular benefit.

See the tirzepatide guide and semaglutide guide.