Is tirzepatide cost-effective compared to insulin degludec based on SURPASS-3?

Yes. Published models consistently show ICERs between $28,000 and $72,000 per QALY gained, well below the $100,000-$150,000 threshold used by most U.S. payers and health technology assessment bodies.

What is the biggest driver of tirzepatide's cost-effectiveness?

Weight loss is the single largest contributor, followed by hypoglycemia avoidance. The 15.2 kg weight difference at 52 weeks between tirzepatide 15 mg and degludec generates substantial projected savings in obesity-related comorbidity costs.

Does the SURPASS-3 cost-effectiveness apply to tirzepatide vs semaglutide?

No. SURPASS-3 compared tirzepatide to insulin degludec. Cost-effectiveness against semaglutide would require separate modeling, and the clinical differences are smaller. SURPASS-2 provides the head-to-head efficacy data for that comparison.

How much does tirzepatide actually cost after insurance?

For commercially insured patients, the manufacturer savings card can reduce the copay to $25/month. Without it, copays range from $25 to $250+ depending on formulary tier. Medicare Part D patients face higher out-of-pocket costs, though the $2,000 annual cap under the Inflation Reduction Act limits total exposure.

Are the economic models biased because Lilly funded them?

The primary published model was Lilly-funded, which warrants caution. However, independent UK-based analyses reached similar conclusions, and the underlying CORE Diabetes Model is externally validated. Base-case assumptions around weight maintenance may be optimistic.

What happens to cost-effectiveness if patients regain weight?

If 50% of weight is regained within five years, the ICER rises from ~$47,000 to ~$72,000 per QALY. Still cost-effective by standard thresholds, but the margin narrows. Real-world persistence data suggests weight regain after discontinuation is a genuine concern.

Does Medicare Part D cover tirzepatide for type 2 diabetes?

Coverage varies by plan. Many Part D plans include tirzepatide but may place it on higher cost-sharing tiers or require prior authorization and step therapy. The Inflation Reduction Act caps annual out-of-pocket spending at $2,000 starting in 2025.

Will biosimilar insulin change the cost-effectiveness calculation?

Yes. Biosimilar insulin degludec entering the market will lower the comparator cost, which mechanically increases the ICER for tirzepatide. Updated analyses incorporating biosimilar pricing are expected in 2026.

How does SURPASS-CVOT affect the economic case for tirzepatide?

SURPASS-CVOT confirmed cardiovascular benefit, which validates the risk-equation projections used in earlier economic models. Updated models incorporating hard MACE endpoint reductions are expected to show improved cost-effectiveness.

Should I choose tirzepatide over insulin purely based on cost-effectiveness data?

Cost-effectiveness is a population-level metric. Individual decisions should weigh personal out-of-pocket cost, weight goals, hypoglycemia risk tolerance, and insurance coverage. The clinical data from SURPASS-3 favors tirzepatide on efficacy, but affordability depends on your specific plan.

SURPASS-3 Cost, Cost-Effectiveness, and Health-Economic Implications

By HealthRX Medical Team

Published May 25, 2026Updated May 25, 2026Last reviewed May 25, 2026

At a glance

| Parameter | Detail | |---|---| | Trial | SURPASS-3 (NCT03882970) | | N | 1,444 | | Intervention | Tirzepatide 5 mg, 10 mg, or 15 mg once weekly | | Comparator | Insulin degludec, titrated to target | | Duration | 52 weeks | | Primary endpoint | Change in HbA1c from baseline | | Key result | All tirzepatide doses superior to insulin degludec for HbA1c reduction and body weight change |

Why SURPASS-3 Is the Key Trial for Economic Modeling

Most cost-effectiveness analyses in the GLP-1 receptor agonist class compare newer agents against older GLP-1s or placebo. SURPASS-3 is different. It tested tirzepatide head-to-head against insulin degludec in adults with type 2 diabetes inadequately controlled on metformin, which means the comparator is the single most prescribed basal insulin worldwide. That head-to-head design gives health economists a direct efficacy bridge between a high-cost injectable peptide and a high-volume insulin, making downstream modeling unusually clean.

At 52 weeks, tirzepatide 15 mg reduced HbA1c by 2.37 percentage points versus 1.34 points for degludec. Weight diverged sharply: tirzepatide 15 mg produced a mean loss of 12.9 kg while the insulin arm gained 2.3 kg. Hypoglycemia rates were lower across all tirzepatide doses. These three endpoints, glycemic control, weight, and hypoglycemia, are the inputs that drive every cost-per-QALY model discussed below.

Published Cost-Effectiveness Analyses

The Lilly-Sponsored IQVIA Model (2022)

The first formal cost-effectiveness analysis using SURPASS-3 data was published by Hunt et al. in Diabetes, Obesity and Metabolism in 2022. The model used the IQVIA CORE Diabetes Model (CDM), a validated microsimulation that projects long-term complications (retinopathy, nephropathy, cardiovascular events, amputation) from short-term trial inputs.

Key assumptions and results:

| Parameter | Value | |---|---| | Time horizon | Patient lifetime (40 years) | | Discount rate | 3% per year (costs and outcomes) | | Perspective | U.S. third-party payer | | Tirzepatide WAC (15 mg) | ~$1,023/month at launch | | Insulin degludec WAC | ~$530/month | | ICER (tirzepatide 15 mg vs degludec) | $46,692 per QALY gained |

The ICER fell well below the commonly cited $100,000-$150,000 per QALY threshold used by ICER and U.S. payers. Sensitivity analyses showed the result was most sensitive to the durability of weight loss and the long-term HbA1c trajectory. When weight regain was modeled at 50% over five years post-trial, the ICER rose to approximately $72,000 per QALY, still under the threshold.

Independent Confirmatory Analyses

A separate analysis by Malkin et al. (2023) used different modeling software and a UK NHS perspective. Their base-case ICER for tirzepatide versus basal insulin was £18,500 per QALY gained, below the NICE £20,000-$30,000 threshold. The concordance between U.S. and UK models strengthens the finding: the clinical advantages measured in SURPASS-3 translate into favorable economics across different healthcare systems.

A third study, presented at the ADA 2023 Scientific Sessions and subsequently published, examined cost-effectiveness from a societal perspective incorporating indirect costs such as lost work productivity related to hypoglycemia and obesity-related disability. Including these indirect costs improved the ICER further, dropping it below $30,000 per QALY.

What Drives the Favorable ICER

The economics are not driven by one factor but by three acting together.

Weight loss offsets drug cost. The 15.2 kg weight difference between tirzepatide 15 mg and degludec at week 52 reduces projected spending on obesity-related comorbidities. Modeling from the CDC Diabetes Cost-Effectiveness Group estimates that each 1-kg sustained weight loss in T2D saves approximately $130-$210 per year in direct medical costs. At the observed magnitude, this generates $2,000-$3,200 per year in avoided downstream costs.

Hypoglycemia avoidance. SURPASS-3 reported clinically significant (blood glucose <54 mg/dL) hypoglycemia in 1.1% of the tirzepatide 15 mg group versus 7.5% of the degludec group. Each severe hypoglycemic episode carries direct costs of $1,200-$2,700 (emergency department) and indirect costs from absenteeism. The ADA Standards of Care emphasize hypoglycemia avoidance as a quality-of-care metric, and payers increasingly track it as a cost driver.

Cardiovascular risk projection. Although SURPASS-3 was not powered for cardiovascular outcomes, the weight and metabolic improvements feed into validated risk equations (UKPDS, RECODe) that project fewer cardiovascular events over a lifetime horizon. The SURPASS-CVOT trial has since confirmed cardiovascular safety and benefit for tirzepatide, providing empirical backing for what earlier models projected.

List Price vs. Net Price: The Gap That Matters

Published cost-effectiveness analyses typically use wholesale acquisition cost (WAC), but WAC rarely reflects what payers actually pay. The gap between list and net price for GLP-1 class agents is among the largest in branded pharmaceuticals.

| Metric | Tirzepatide (Mounjaro) | Insulin degludec (Tresiba) | |---|---| | WAC per month (2024) | ~$1,023 | ~$530 | | Estimated net price (after rebates) | ~$550-$650 | ~$280-$350 | | Net price ratio | ~1.7-2.3x degludec | Reference |

Data on actual net prices comes from SSR Health analyses of manufacturer SEC filings and investor disclosures. When models substitute net pricing for WAC, the ICER shifts downward, sometimes dramatically. At the midpoint net-price estimate, the Hunt et al. model ICER drops from $46,692 to roughly $28,000-$35,000 per QALY.

This distinction matters because formulary committees at pharmacy benefit managers (PBMs) negotiate on net price. The FDA-approved prescribing information for tirzepatide does not address cost, but payer decisions hinge on confidential rebate agreements that can shift the effective cost by 30-45%.

Payer Coverage and Formulary Implications

As of 2025, tirzepatide coverage for type 2 diabetes is broad among commercial payers but fragmented under Medicare Part D. Most commercial plans cover Mounjaro on Tier 3 (preferred brand) or Tier 4 (non-preferred brand) with prior authorization requiring documented metformin use and an HbA1c above 7.0%. Step therapy through a sulfonylurea or older GLP-1 is sometimes required.

Medicare Part D coverage is more restrictive. The Inflation Reduction Act's $2,000 out-of-pocket cap changes the patient-facing calculus starting in 2025, but it does not change formulary placement. Plans can still relegate tirzepatide to non-preferred tiers or exclude it entirely when a preferred GLP-1 (typically semaglutide) is available.

The economic argument from SURPASS-3 data, that tirzepatide produces superior outcomes versus basal insulin, gives clinicians a concrete appeal pathway when prior authorizations are denied. A letter citing the SURPASS-3 primary results alongside the published ICER data has become a standard template in endocrinology practices.

Limitations of Current Economic Models

All published models share structural assumptions that deserve scrutiny.

Trial-to-lifetime extrapolation. SURPASS-3 provides 52 weeks of data. Models project 30-40 year outcomes using risk equations calibrated on older populations (UKPDS was enrolled in the 1970s-1990s). The degree to which modern complication rates map onto those risk equations is uncertain.

Weight regain assumptions vary wildly. Some models assume 100% weight maintenance; others assume 50% regain by year five. Real-world GLP-1 persistence data from Weiss et al. (2024) suggests that approximately 40-50% of patients discontinue within 24 months, and weight regain after discontinuation is substantial. Models that assume indefinite adherence overestimate QALYs.

Comparator choice matters. SURPASS-3 compared tirzepatide to insulin degludec, not to semaglutide or other GLP-1s. Cost-effectiveness versus another GLP-1 receptor agonist would produce a very different ICER, and head-to-head GLP-1 vs. dual-agonist data remains limited to the SURPASS-2 trial versus semaglutide 1 mg.

Industry sponsorship. The Hunt et al. analysis was funded by Eli Lilly. While the CORE Diabetes Model is independently validated, the choices around input parameters (100% weight maintenance in the base case, WAC pricing) favor the intervention arm. Independent replication using conservative assumptions is ongoing.

The Individual Patient Value Calculation

For a patient sitting in a clinic deciding between tirzepatide and basal insulin, the population-level ICER is less relevant than personal out-of-pocket cost, injection burden, and expected clinical benefit.

The practical decision framework:

Check insurance tier and copay. If tirzepatide lands on a specialty tier with a $200+/month copay, the cost gap relative to a $25-$50 insulin copay may outweigh the clinical advantage for some patients.
Assess weight as a co-target. For patients with BMI above 30, the 12-15 kg weight advantage from SURPASS-3 carries value beyond glycemia. This is especially relevant for patients with concurrent MASLD, obstructive sleep apnea, or osteoarthritis.
Factor in hypoglycemia risk. For patients in safety-sensitive occupations (commercial drivers, heavy-equipment operators), the lower hypoglycemia rate has direct occupational and financial value.
Consider manufacturer savings programs. Lilly's savings card program reduces out-of-pocket costs to $25/month for commercially insured patients. This does not apply to government insurance.

Where the Evidence Is Headed

Several ongoing analyses will refine the economic picture. Real-world evidence studies using U.S. claims databases (Optum, MarketScan) are comparing actual healthcare utilization between tirzepatide and insulin initiators. The SURPASS-CVOT cardiovascular outcome data will feed directly into updated economic models, potentially improving the ICER if hard cardiovascular endpoints (MACE) are reduced. Biosimilar insulin degludec entering the market in 2025 will lower the comparator cost, which could narrow the cost-effectiveness margin.

Frequently asked questions

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References

Ludvik B, Giorgino F, Jódar E, et al. Once-weekly tirzepatide versus once-daily insulin degludec as add-on to metformin with or without SGLT2 inhibitors in patients with type 2 diabetes (SURPASS-3): a randomised, open-label, parallel-group, phase 3 trial. Lancet. 2021;398(10300):583-598. PubMed
Hunt B, Malkin SJP, Myland M, et al. Cost-effectiveness of tirzepatide versus insulin degludec in patients with type 2 diabetes in the United States. Diabetes Obes Metab. 2023;25(1):238-247. PubMed
Malkin SJP, Hunt B, Gad AYS, et al. Cost-effectiveness of tirzepatide versus insulin degludec in the UK. Diabetes Ther. 2023;14(8):1345-1361. PubMed
Nicholls SJ, Bhatt DL, Buse JB, et al. Tirzepatide and cardiovascular outcomes in participants with type 2 diabetes: SURPASS-CVOT. N Engl J Med. 2024. PubMed
Frías JP, Davies MJ, Rosenstock J, et al. Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes (SURPASS-2). N Engl J Med. 2021;385(6):503-515. PubMed
Tirzepatide (Mounjaro) prescribing information. U.S. Food and Drug Administration. FDA