Tirzepatide for Type 2 Diabetes: What the SURPASS Trials Show
If you have type 2 diabetes and you've been researching tirzepatide, you may have come across it mainly in the context of weight loss. That's understandable. The headlines around Mounjaro and Zepbound
In this article
If you have type 2 diabetes and you've been researching tirzepatide, you may have come across it mainly in the context of weight loss. That's understandable. The headlines around Mounjaro and Zepbound have focused heavily on how much weight people lose. But tirzepatide was developed with type 2 diabetes as its primary indication, and the clinical evidence base for its effects on blood sugar control, cardiovascular risk, and metabolic health is substantial.
This article covers what the SURPASS trial series and related studies actually show for people specifically managing type 2 diabetes, including the landmark head-to-head comparison with semaglutide.
*The trial data discussed in this article is based on branded Mounjaro (tirzepatide). Compounded tirzepatide is not FDA-approved, including for the treatment of type 2 diabetes, and branded trial results should not be assumed to apply to compounded formulations. This article is for educational and informational purposes only and does not constitute medical advice. Results vary by individual. Consult your licensed healthcare provider before starting, stopping, or adjusting any medication or treatment.*
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How Tirzepatide Works Differently from Other GLP-1 Medications
Tirzepatide belongs to a new class of medications that activate two hormone receptors simultaneously: GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide). This dual-agonist mechanism is what sets it apart from semaglutide, liraglutide, and other GLP-1-only medications.
In people with type 2 diabetes, both of these hormone signaling pathways are often impaired. The GLP-1 pathway is well-known from other medications: it stimulates insulin release after meals, suppresses glucagon (reducing liver glucose output), slows gastric emptying, and sends satiety signals to the brain.
GIP activation adds a complementary layer. GIP receptors are present in the pancreas, adipose tissue, and brain. GIP enhances insulin secretion through a slightly different mechanism than GLP-1, and the two pathways together appear to work more synergistically than either would alone. This may explain why tirzepatide tends to produce larger HbA1c reductions and greater weight loss than comparably dosed GLP-1 receptor agonists.
For someone managing type 2 diabetes, this combination addresses multiple drivers of the disease simultaneously: blunted incretin response, excess glucagon secretion, and the insulin resistance associated with adipose tissue dysfunction.
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Blood Sugar Control: What SURPASS-1 Shows
The SURPASS-1 trial (PMID: 34186022, Rosenstock et al., Lancet 2021) was the foundational efficacy study for tirzepatide monotherapy in type 2 diabetes. It enrolled 478 adults with type 2 diabetes on diet and exercise alone, with a mean baseline HbA1c of 7.9%, and followed them for 40 weeks.
The results were striking for a monotherapy trial. Tirzepatide reduced HbA1c by an average of:
- 1.87 percentage points with 5 mg
- 1.89 percentage points with 10 mg
- 2.07 percentage points with 15 mg
To put these numbers in context: an HbA1c above 7.0% is generally considered outside target range. A reduction of 1 percentage point is clinically meaningful for diabetes complication risk. Tirzepatide was moving people by roughly twice that amount from a starting point that was only modestly elevated.
The proportion of participants reaching HbA1c below 7.0% was 87 to 92% across tirzepatide doses, compared to 20% in the placebo group. A substantial portion (31 to 52%) reached HbA1c below 5.7%, which represents normoglycemia. That degree of glycemic response is uncommon for a monotherapy trial.
Weight loss was dose-dependent as well, ranging from 7.0 to 9.5 kg across the three doses.
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Head-to-Head Against Semaglutide: SURPASS-2
The SURPASS-2 trial (PMID: 34170647, Frías et al., N Engl J Med 2021) is the most discussed study in tirzepatide's clinical dossier because it directly compared tirzepatide to semaglutide 1 mg weekly, the maximum approved dose of semaglutide for type 2 diabetes.
The trial enrolled 1,879 adults with type 2 diabetes, with a mean baseline HbA1c of 8.28%, and followed them for 40 weeks in an open-label design.
The primary finding: all three doses of tirzepatide were noninferior and superior to semaglutide for HbA1c reduction.
Mean HbA1c reductions were:
- Tirzepatide 5 mg: -2.01 percentage points
- Tirzepatide 10 mg: -2.24 percentage points
- Tirzepatide 15 mg: -2.30 percentage points
- Semaglutide 1 mg: -1.86 percentage points
Weight loss was also greater with tirzepatide across all doses. The estimated additional weight loss versus semaglutide was 1.9 kg at 5 mg, 3.6 kg at 10 mg, and 5.5 kg at 15 mg, all statistically significant.
The gastrointestinal side effect profile was comparable. Nausea occurred in 17 to 22% of tirzepatide patients and 18% of semaglutide patients. Diarrhea and vomiting rates were similarly matched. Despite the greater metabolic effect of tirzepatide, tolerability was not substantially worse than the established comparator.
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Weight Loss in People with Type 2 Diabetes: SURMOUNT-2
The SURPASS trials focused on HbA1c as a primary endpoint. SURMOUNT-2 (PMID: 37385275, Garvey et al., Lancet 2023) was designed specifically to assess weight loss in people living with both obesity and type 2 diabetes, using a 72-week follow-up.
The 938 participants had a mean baseline HbA1c of 8.02% and a mean body weight of 100.7 kg. They were randomized to tirzepatide 10 mg, tirzepatide 15 mg, or placebo.
Results at 72 weeks:
- Tirzepatide 10 mg: -12.8% body weight
- Tirzepatide 15 mg: -14.7% body weight
- Placebo: -3.2% body weight
These weight loss figures are meaningful for type 2 diabetes management beyond the scale reading. Losing 5 to 10% of body weight in people with type 2 diabetes can meaningfully reduce insulin resistance, sometimes lowering the need for other glucose-lowering medications. Weight losses in the 12 to 15% range observed in SURMOUNT-2 produce substantial reductions in adipose-driven insulin resistance and may alter the disease trajectory in ways that extend well beyond glycemic control.
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Cardiovascular Outcomes: SURPASS-CVOT
For people with type 2 diabetes, cardiovascular disease is the leading cause of death. Any glucose-lowering medication that increases cardiovascular risk is not a viable option regardless of its efficacy on blood sugar. The SURPASS-CVOT trial (PMID: 41406444, Nicholls et al., N Engl J Med 2025) provides the dedicated cardiovascular outcomes data for tirzepatide.
The trial enrolled 13,299 patients with type 2 diabetes and established atherosclerotic cardiovascular disease, comparing tirzepatide to dulaglutide (another GLP-1 receptor agonist) over a median follow-up of roughly four years.
The primary cardiovascular composite endpoint (cardiovascular death, myocardial infarction, or stroke) occurred in 12.2% of the tirzepatide group versus 13.1% of the dulaglutide group, giving a hazard ratio of 0.92 (95.3% CI, 0.83 to 1.01; P = 0.003 for noninferiority).
Tirzepatide was noninferior to dulaglutide, an already-established cardioprotective GLP-1 medication. The trial did not achieve statistical significance for superiority (P = 0.09). What the data establishes is that tirzepatide does not increase cardiovascular risk and carries a cardiovascular safety profile comparable to a medication already recommended for high-risk patients.
This is a meaningful distinction for people with type 2 diabetes and established heart disease or multiple cardiovascular risk factors. It means tirzepatide can be used without concern about aggravating cardiovascular risk, and the metabolic benefits it delivers come without a cardiovascular trade-off.
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Kidney Protection: SURPASS-4 Post-Hoc Data
Type 2 diabetes is the leading cause of chronic kidney disease worldwide, and kidney function decline is one of the most consequential long-term complications of the disease. Tirzepatide's effects on kidney function are emerging from post-hoc analyses of the SURPASS trials.
A SURPASS-4 post-hoc analysis (PMID: 37267479, Heerspink et al., Diabetes Care 2023) examined kidney function using both creatinine-based and cystatin C-based eGFR measures. The distinction matters because creatinine-based eGFR can be influenced by muscle mass changes that accompany significant weight loss, potentially overstating kidney function decline. Cystatin C is not affected by muscle mass.
Among participants with type 2 diabetes and high cardiovascular risk, tirzepatide produced a mean eGFR-creatinine change of -2.5 mL/min/1.73 m2, compared to -3.9 mL/min/1.73 m2 with insulin glargine, suggesting better kidney function preservation over 52 weeks. The cystatin C-based analysis confirmed this directional benefit, supporting the finding as genuine rather than an artifact of muscle mass changes.
This is a preliminary signal rather than a definitive kidney outcomes trial. Dedicated tirzepatide renal outcomes research is ongoing. However, the available data is consistent with the direction established by the class: GLP-1-based therapies appear to slow kidney function decline in people with type 2 diabetes at meaningful risk.
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How Tirzepatide Fits Into Type 2 Diabetes Treatment
Tirzepatide is not a first-line medication for type 2 diabetes. Clinical guidelines generally recommend starting with metformin and lifestyle modification. Tirzepatide is typically considered when someone needs meaningfully better blood sugar control, has cardiovascular or kidney risk that makes a GLP-1-based therapy appropriate, or is seeking substantial weight reduction as part of their diabetes management.
That said, the evidence base is shifting how providers think about sequencing. Given tirzepatide's cardiovascular safety data and its superior glycemic and weight outcomes versus established comparators, many endocrinologists and primary care providers are considering it earlier in the treatment sequence for high-risk patients, particularly those with established cardiovascular disease or early diabetic kidney disease.
Tirzepatide can be combined with metformin and SGLT-2 inhibitors. When used alongside insulin or sulfonylureas, providers typically reduce doses of those medications when tirzepatide is added, because the combination can increase hypoglycemia risk. If you are currently on either of these drug classes, your provider should discuss dose adjustments before you start.
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Side Effects in People with Type 2 Diabetes
The side effect profile of tirzepatide in type 2 diabetes trials is consistent with what's seen in the general population. Gastrointestinal effects are the most common and tend to concentrate during the early months of dose escalation.
In SURPASS-1, nausea occurred in 12 to 18% of participants versus 6% with placebo. Diarrhea affected 12 to 14% versus 8%. Vomiting occurred in 2 to 6% across doses versus 2% with placebo. For most people, these effects diminish considerably after the first 8 to 12 weeks as the body adjusts.
An important T2D-specific consideration: tirzepatide does not cause hypoglycemia on its own because it stimulates insulin secretion only in response to elevated blood glucose (glucose-dependent mechanism). In SURPASS-1, which enrolled people on diet and exercise alone, there were no clinically significant hypoglycemia events. However, when tirzepatide is combined with insulin or sulfonylureas, the risk of low blood sugar increases. Dose adjustments of the accompanying medication are typically required.
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Compounded Tirzepatide and Type 2 Diabetes
This article describes results from clinical trials of branded Mounjaro, FDA-approved tirzepatide manufactured by Eli Lilly. These results reflect a specific formulation, dosing protocol, and patient population studied under controlled conditions.
Compounded tirzepatide is not FDA-approved. It is not approved for the treatment of type 2 diabetes or for any other indication. Compounded preparations are made by licensed 503A or 503B compounding pharmacies and require a prescription from a licensed provider. Formulation, dosing, and excipients may differ from the branded product, and branded clinical trial results should not be assumed to apply to compounded formulations.
People with type 2 diabetes who are considering compounded tirzepatide should discuss this explicitly with a provider who understands their full medication list, current glycemic control, and any cardiovascular or kidney risk factors. The considerations for someone managing diabetes alongside weight loss are meaningfully different from those for someone without diabetes.
Cost is a real factor. Branded Mounjaro can cost over $1,000 per month without insurance. Compounded tirzepatide is available at significantly lower cost through telehealth platforms. See [Compounded Tirzepatide: A Complete Guide](/resources/compounded-tirzepatide-guide) for a detailed breakdown of what compounding means, how to evaluate pharmacy quality, and what to expect from costs.
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Who May Qualify for Tirzepatide with Type 2 Diabetes
In the context of type 2 diabetes, tirzepatide may be appropriate if you:
- Have type 2 diabetes with suboptimal blood sugar control despite current medications
- Have established cardiovascular disease or multiple cardiovascular risk factors
- Have obesity alongside your diabetes and need meaningful weight reduction to improve insulin sensitivity
- Are seeking better HbA1c control than currently available with your regimen
- Want once-weekly injection rather than daily medication
For a full look at who qualifies for GLP-1 medications in general, see [Who Qualifies for GLP-1 Medications](/resources/who-qualifies-for-glp1-medications).
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The Clinical Picture
The SURPASS trial series establishes tirzepatide as a highly effective option for people managing type 2 diabetes who need better glycemic control, meaningful weight reduction, or both. The evidence base covers:
- HbA1c reductions of 1.87 to 2.07 percentage points as monotherapy versus placebo (SURPASS-1)
- Superior HbA1c reduction compared to semaglutide 1 mg across all doses, with greater weight loss at each dose level (SURPASS-2)
- 12.8 to 14.7% body weight reduction in people with obesity and type 2 diabetes at 72 weeks (SURMOUNT-2)
- Noninferior cardiovascular safety compared to dulaglutide in high-risk patients (SURPASS-CVOT)
- Favorable preliminary kidney function data versus insulin glargine in high-risk T2D patients (SURPASS-4 post-hoc)
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Talk to a Provider
If you have type 2 diabetes and want to understand whether tirzepatide fits your situation, a licensed provider is the right starting point. They can review your current medication list, assess your glycemic trajectory, evaluate cardiovascular and kidney risk, and help you set realistic goals for blood sugar and weight management.
Prescriva's platform connects patients with licensed independent providers who care for people across a range of metabolic health goals. If you haven't had a consultation yet, [start your assessment](/get-started) to connect with a licensed provider.
*Results vary. Compounded tirzepatide is not FDA-approved. This content discusses branded Mounjaro clinical trial data; branded results should not be assumed to apply to compounded preparations. This content is for informational purposes only and does not constitute medical advice. Always consult a licensed healthcare provider before starting, adjusting, or stopping any medication. Blue Oak Services LLC dba Prescriva is a management services organization and does not practice medicine or make clinical decisions.*
Sources
- Rosenstock J et al. SURPASS-1: Efficacy and safety of tirzepatide monotherapy in type 2 diabetes. *Lancet.* 2021. PMID: 34186022
- Frías JP et al. SURPASS-2: Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes. *New England Journal of Medicine.* 2021. PMID: 34170647
- Garvey WT et al. SURMOUNT-2: Tirzepatide for obesity in people with type 2 diabetes. *Lancet.* 2023. PMID: 37385275
- Nicholls SJ et al. SURPASS-CVOT: Cardiovascular outcomes with tirzepatide versus dulaglutide in type 2 diabetes. *New England Journal of Medicine.* 2025. PMID: 41406444
- Heerspink HJL et al. Effects of tirzepatide versus insulin glargine on cystatin C-based kidney function: a SURPASS-4 post hoc analysis. *Diabetes Care.* 2023. PMID: 37267479
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References
- Rosenstock J et al. SURPASS-1: Efficacy and safety of tirzepatide monotherapy in type 2 diabetes. Lancet. (2021).
- Frías JP et al. SURPASS-2: Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes. New England Journal of Medicine. (2021).
- Garvey WT et al. SURMOUNT-2: Tirzepatide for obesity in people with type 2 diabetes. Lancet. (2023).
- Nicholls SJ et al. SURPASS-CVOT: Cardiovascular outcomes with tirzepatide versus dulaglutide in type 2 diabetes. New England Journal of Medicine. (2025).
- Heerspink HJL et al. Effects of tirzepatide versus insulin glargine on cystatin C-based kidney function: a SURPASS-4 post hoc analysis. Diabetes Care. (2023).
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