Tirzepatide vs Semaglutide: Complete Comparison (2026 Data)

Tirzepatide and semaglutide are the two most widely prescribed GLP-1 class drugs for weight loss and type 2 diabetes. Tirzepatide (sold as Mounjaro for diabetes and Zepbound for weight loss) is a dual GLP-1/GIP agonist. Semaglutide (sold as Ozempic for diabetes, Wegovy for weight loss, and Rybelsus as an oral formulation) is a GLP-1 agonist.

The SURMOUNT-5 head-to-head trial published in 2025 provides the definitive comparison: tirzepatide produces about 47% more weight loss than semaglutide at maximum doses.

Side-by-Side Comparison

	Tirzepatide	Semaglutide
Brand names	Mounjaro (T2D), Zepbound (weight loss)	Ozempic (T2D), Wegovy (weight loss), Rybelsus (oral)
Manufacturer	Eli Lilly	Novo Nordisk
Mechanism	Dual agonist: GLP-1 + GIP	Single agonist: GLP-1
Molecule type	Modified GIP peptide with GLP-1 activity	Modified GLP-1 peptide
Max dose	15 mg (injection)	2.4 mg (injection) / 50 mg (oral tablet)
Dosing	Once weekly (injection only)	Once weekly (injection) or once daily (oral)
Half-life	~5 days	~7 days
FDA approvals	T2D (2022), Weight loss (2023)	T2D (2017), Weight loss (2021), CV risk reduction (2024)
Oral option	No	Yes (Rybelsus, oral Wegovy)
CV outcomes trial	SURPASS-CVOT (ongoing)	SELECT (completed — 20% MACE reduction)

The SURMOUNT-5 Head-to-Head Trial

SURMOUNT-5 is the landmark study that directly compares tirzepatide and semaglutide. Published in The New England Journal of Medicine in 2025, it is the first randomized, double-blind, head-to-head trial between these two drugs.

Trial Design

Participants: 751 adults with BMI 30+ (or 27+ with weight-related comorbidity)
Duration: 72 weeks
Doses: Tirzepatide escalated to max 15 mg; semaglutide escalated to max 2.4 mg
Primary endpoint: Percent change in body weight at 72 weeks

Key Results

Outcome	Tirzepatide	Semaglutide
Average weight loss	-20.2%	-13.7%
Difference	6.5 percentage points more	—
Lost at least 5%	94%	85%
Lost at least 10%	82%	66%
Lost at least 15%	70%	47%
Lost at least 20%	55%	28%
Lost at least 25%	35%	12%

What This Means

Tirzepatide produced nearly 50% more relative weight loss than semaglutide. At the 20% threshold — often considered clinically transformative — nearly twice as many tirzepatide patients (55%) achieved it compared to semaglutide (28%).

The trial confirms what separate trial programs (SURMOUNT vs STEP) had suggested but could not definitively prove due to different patient populations.

Weight Loss Across All Major Trials

Drug	Trial	Indication	Duration	Weight Loss
Tirzepatide 15 mg	SURMOUNT-1	Obesity	72 weeks	-22.5%
Tirzepatide	SURMOUNT-5	Obesity (head-to-head)	72 weeks	-20.2%
Tirzepatide 15 mg	SURMOUNT-2	Obesity + T2D	72 weeks	-14.7%
Semaglutide 2.4 mg	STEP 1	Obesity	68 weeks	-14.9%
Semaglutide 2.4 mg	SURMOUNT-5	Obesity (head-to-head)	72 weeks	-13.7%
Semaglutide 2.4 mg	STEP 2	Obesity + T2D	68 weeks	-9.6%
Oral semaglutide 50 mg	OASIS 1	Obesity	68 weeks	-15.1%

Diabetes Management: SURPASS vs SUSTAIN

Both drugs are approved for type 2 diabetes, but tirzepatide has shown stronger glucose control.

Outcome	Tirzepatide (SURPASS)	Semaglutide (SUSTAIN)
HbA1c reduction	Up to -2.58%	Up to -1.8%
HbA1c below 5.7% (normal)	Up to 46%	Not reported at this threshold
Weight loss (T2D trials)	-12.9 kg (SURPASS-1)	-6.5 kg (SUSTAIN-1)
Head-to-head vs semaglutide	Superior (SURPASS-2 vs Ozempic 1 mg)	—

In SURPASS-2, tirzepatide was tested head-to-head against semaglutide 1 mg (Ozempic) for type 2 diabetes. Tirzepatide was superior on both HbA1c reduction and weight loss at all three dose levels (5, 10, 15 mg).

Side Effects and Tolerability

Side Effect	Tirzepatide (SURMOUNT-5)	Semaglutide (SURMOUNT-5)
Any GI event	~70%	~65%
Nausea	28%	26%
Diarrhea	22%	18%
Vomiting	13%	10%
Constipation	14%	12%
Discontinuation (AEs)	~5%	~3%

Both drugs have similar GI side effect profiles. Most side effects are mild to moderate and occur during the dose escalation period. Tirzepatide has slightly higher rates overall, consistent with its greater metabolic effect. Both drugs use a gradual dose titration schedule to minimize GI symptoms.

Hair Loss

Hair loss (alopecia) has been reported with both drugs at low rates. In SURMOUNT trials, ~5% of tirzepatide patients reported hair loss (vs ~1% placebo). In STEP trials, ~3% of semaglutide patients reported it. Hair loss with GLP-1 drugs is thought to be telogen effluvium — a temporary shedding caused by rapid weight loss rather than the drug itself.

Cost and Access

	Tirzepatide	Semaglutide
Weight loss brand	Zepbound (~$1,059/mo list)	Wegovy (~$1,349/mo list)
Diabetes brand	Mounjaro (~$1,059/mo list)	Ozempic (~$935/mo list)
Oral option	None	Rybelsus (T2D), oral Wegovy (weight loss)
Direct pricing	LillyDirect: ~$550/mo	Varies by program
Insurance coverage	Growing	Broader (earlier approval + CV data)

Oral Options

Semaglutide has a significant advantage in oral availability. Oral Wegovy (semaglutide tablets) was FDA-approved in 2025 for weight loss, making it the first oral GLP-1 specifically approved for obesity. Rybelsus (oral semaglutide) has been available for type 2 diabetes since 2019.

Tirzepatide has no oral formulation. While Eli Lilly has oral tirzepatide in development, it is still in clinical trials.

For patients who prefer to avoid injections, semaglutide currently offers the only approved oral GLP-1 option for weight loss.

Where Does Retatrutide Fit?

Retatrutide is the first triple agonist — targeting GLP-1, GIP, and glucagon receptors. In Phase 3 trials, it produced 28.7% body weight loss, the largest result for any anti-obesity medication. The addition of glucagon receptor agonism increases energy expenditure and drives liver fat reduction.

Retatrutide is not yet FDA-approved (expected 2027). For a detailed comparison with tirzepatide, see Retatrutide vs Tirzepatide.

Frequently Asked Questions

Is tirzepatide better than semaglutide?

For weight loss and glucose control, tirzepatide produces superior results — confirmed in head-to-head trials (SURMOUNT-5 and SURPASS-2). However, semaglutide has proven cardiovascular protection (SELECT trial), an oral formulation, and a longer safety track record. The best choice depends on individual medical needs.

What is the SURMOUNT-5 trial?

SURMOUNT-5 is the first randomized, double-blind head-to-head trial comparing tirzepatide (up to 15 mg) with semaglutide (up to 2.4 mg) for weight loss. Published in 2025, it showed tirzepatide produced -20.2% weight loss vs -13.7% for semaglutide at 72 weeks.

Does tirzepatide or semaglutide cause more side effects?

Both have similar GI side effect profiles (nausea, diarrhea, vomiting, constipation). Tirzepatide has slightly higher rates overall in head-to-head comparison, but discontinuation rates are similar (~5% vs ~3%). Both are generally well tolerated.

Can tirzepatide cause hair loss?

Hair loss has been reported at low rates (~5% in SURMOUNT trials vs ~1% placebo). This is thought to be telogen effluvium — temporary hair shedding caused by rapid weight loss, not a direct drug effect. Similar rates occur with semaglutide and other weight loss interventions.

Is there an oral tirzepatide?

Not yet. Eli Lilly has oral tirzepatide in clinical development, but it has not been approved. Currently, semaglutide is the only GLP-1 drug available in oral form for both diabetes (Rybelsus) and weight loss (oral Wegovy).

Which is better for type 2 diabetes — tirzepatide or semaglutide?

Tirzepatide demonstrated superior HbA1c reduction and weight loss in the SURPASS-2 head-to-head trial against semaglutide 1 mg (Ozempic). Both are effective, but tirzepatide produced greater glucose control across all dose levels.

Sources

Frías, J.P., et al. (2025). Tirzepatide vs Semaglutide for Weight Loss (SURMOUNT-5). New England Journal of Medicine. DOI: 10.1056/NEJMoa2501113
Jastreboff, A.M., et al. (2022). Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). New England Journal of Medicine. DOI: 10.1056/NEJMoa2206038
Wilding, J.P.H., et al. (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). New England Journal of Medicine. DOI: 10.1056/NEJMoa2032183
Frías, J.P., et al. (2021). Tirzepatide versus Semaglutide Once Weekly in Type 2 Diabetes (SURPASS-2). New England Journal of Medicine. DOI: 10.1056/NEJMoa2107519
Lincoff, A.M., et al. (2023). Semaglutide and Cardiovascular Outcomes (SELECT). New England Journal of Medicine. DOI: 10.1056/NEJMoa2307563

How we keep this honest

What this is: Educational information, not medical advice. It reports published research — it doesn’t recommend that you use, obtain, or supply anything.
Regulatory status: Retatrutide and similar peptides are investigational — not approved by the FDA or any regulator. Semaglutide and tirzepatide are prescription-only medicines, available only through a licensed prescriber.
Our standard: Every claim traces to a primary source. We label the strength of evidence and flag estimates as estimates — never as clinical fact.
No commercial ties: We don’t sell, supply, or link to suppliers of any medicine, and aren’t affiliated with any manufacturer.

Do not make decisions about your health without consulting a qualified healthcare provider. For trial enrolment, see ClinicalTrials.gov. More on how we review.

Sources