Zepbound (tirzepatide (injection)): the 2026 GLP-1 guide
Lilly's once-weekly tirzepatide — strongest weight loss in class (~22% in SURMOUNT-1). LillyDirect from $299/mo; Medicare Bridge KwikPen only.
Overview
Zepbound is Eli Lilly’s tirzepatide subcutaneous injection, FDA-approved on November 8, 2023 for chronic weight management in adults with obesity (BMI ≥ 30) or overweight (BMI ≥ 27) plus at least one weight-related comorbidity. It is the same molecule as Mounjaro but with a weight-management indication and a separate brand for that label.
Tirzepatide is a dual GIP / GLP-1 receptor agonist — unlike single-pathway GLP-1 agonists (semaglutide in Wegovy/Ozempic, liraglutide in Saxenda), it activates both glucose-dependent insulinotropic polypeptide and GLP-1 receptors. The dual mechanism is the leading hypothesis for tirzepatide’s stronger weight-loss effect compared to semaglutide.
Clinical Efficacy
In SURMOUNT-1 (2,539 adults with obesity but without T2D), Zepbound produced a 22.5% mean body-weight reduction at 72 weeks at the 15 mg dose (efficacy estimand) vs 2.4% on placebo. The 5 mg dose produced 16% loss; 10 mg produced 21.4%1.
This is the highest mean weight loss in the GLP-1 class to date — substantially higher than oral options (Foundayo ~12%, Wegovy Tablets ~14%) and modestly higher than weekly Wegovy injection (~15%).
Dosing & Titration
Six approved dose strengths, available as both pre-filled single-dose pens and multi-dose KwikPens, plus single-dose vials at lower strengths via LillyDirect cash:
- 2.5 mg — starting dose, 4 weeks only (titration step, not therapeutic)
- 5 mg — first maintenance dose
- 7.5 mg — escalation step
- 10 mg — common maintenance
- 12.5 mg — escalation step
- 15 mg — maximum dose
Schedule: start at 2.5 mg subcutaneously once weekly for 4 weeks. Increase the dose in 2.5 mg increments after at least 4 weeks at the prior dose, until reaching the maintenance dose. Maximum is 15 mg weekly. Inject in the abdomen, thigh, or upper arm; rotate sites2.
Side Effects
Boxed warning — Risk of Thyroid C-Cell Tumors
Tirzepatide causes thyroid C-cell tumors in rats at clinically relevant exposures; whether it causes the same in humans (including medullary thyroid carcinoma, MTC) is unknown. Zepbound is contraindicated in patients with a personal or family history of MTC or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2)2.
Most common adverse reactions (Zepbound 15 mg vs placebo)
| Adverse reaction | 15 mg | Placebo |
|---|---|---|
| Nausea | 28% | 8% |
| Diarrhea | 23% | 8% |
| Vomiting | 13% | 2% |
| Constipation | 11% | 5% |
| Dyspepsia | 10% | 4% |
| Injection-site reactions | 8% | 2% |
| Fatigue | 7% | 3% |
GI events typically peak during titration (weeks 4–12) and improve as tolerance develops.
Contraindications
- Personal or family history of medullary thyroid carcinoma (MTC)
- Multiple Endocrine Neoplasia syndrome type 2 (MEN 2)
- Known serious hypersensitivity to tirzepatide or excipients
Use is not recommended in patients with severe gastroparesis.
2026 Availability
Zepbound is on Part D Tier 4 with most plans, with prior authorization typically required for chronic-weight-management indication.
Medicare GLP-1 Bridge: KwikPen only. Eligible Part D beneficiaries pay $50/month from July 1, 2026, but only for the KwikPen formulation — single-dose pens and vials are excluded from the Bridge.
Cash pay via LillyDirect Journey Program: 2.5 mg vials at $299/month, 5 mg vials at $399/month when refilled within 45 days. Higher doses up to $1,049/month at the standard list. Commercial-insurance copay varies by plan; with prior auth approved, expect Tier 4 copay in the $25–$60 range.
For oral alternatives at lower mean efficacy: see Foundayo (~12% weight loss, $149/mo) and Wegovy Tablets (~14%, $149/mo).
Footnotes
-
Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med 2022;387:205-216. (SURMOUNT-1) ↩
-
Zepbound Prescribing Information — DailyMed (NIH), revised April 2026. ↩ ↩2
Your monthly price for Zepbound
Show all 3 priced paths
- Insurance copay (in-network, post prior-auth)Requires prior auth$50/mo
- LillyDirect self-pay$299/mo
- Pharmacy list cash price$1059/mo
Zepbound: frequently asked questions
Why is Zepbound stronger than the oral GLP-1s?
Is Zepbound covered under the Medicare GLP-1 Bridge?
How does Zepbound compare to Mounjaro?
What's the cheapest way to get Zepbound?
Sources & citations
Every clinical claim on this page traces to one of the 3 sources below — primarily FDA-approved labels via DailyMed (NIH) and peer-reviewed trial papers. Last reviewed ; next review due .
- 1 Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1)Primary NEJM Accessed
- 2 ZEPBOUND (tirzepatide) injection — Prescribing InformationPrimary National Library of Medicine (DailyMed) Published Accessed
- 3 Lilly launches additional Zepbound vial doses and offers new self-pay savingsPrimary Eli Lilly Investor Relations Accessed