Are Zepbound® Vials Covered by Insurance the Same Way as Pens?

Why the Vial vs. Pen Distinction Matters to Insurers

The formulation difference is not just packaging. When a pharmacy submits a claim, it uses the National Drug Code (NDC) printed on the box. Zepbound autoinjector pens and Zepbound single-dose vials carry distinct NDC numbers, so a plan that added the pen NDC to its formulary before vials launched in late 2024 may return a "not covered" rejection for the vial NDC even if the drug itself is tirzepatide at the same dose.

How NDC Codes Drive Formulary Decisions

Every drug product on the U.S. Market receives a unique 10- or 11-digit NDC from the FDA. Pharmacy benefit managers (PBMs) and insurers build formularies by loading specific NDC codes, not drug names alone. When Eli Lilly introduced Zepbound single-dose vials in late 2024 at a lower list price, those vials received new NDC numbers. Plans that had not yet updated their formulary files simply had no entry for those codes.

The FDA's NDC directory confirms that different package types of the same drug carry separate codes. [1] A claim submitted with an unlisted NDC returns a B/27 or "product not on formulary" rejection at the point of sale.

The Prior-Authorization Problem

Prior authorization (PA) requirements for GLP-1 receptor agonists used for obesity are near-universal among commercial insurers. A 2023 analysis published in JAMA Network Open found that 90% of large commercial health plans required PA for branded GLP-1 agents prescribed for weight management. [2] PA criteria typically require:

• A BMI of 30 or higher, or BMI of 27 or higher with at least one weight-related comorbidity (hypertension, type 2 diabetes, dyslipidemia, or obstructive sleep apnea)
• Documentation of a structured diet and exercise program tried for at least 3 to 6 months
• Absence of contraindications such as personal or family history of medullary thyroid carcinoma or MEN2

These PA criteria were written around the pen formulation because vials launched after most plans finalized their 2024 benefit designs. Some plans have not updated their PA criteria documents to explicitly name vials. That gap can cause automatic rejections even when a patient meets every clinical threshold.

The Clinical Case for Tirzepatide Coverage

Tirzepatide's efficacy data make the coverage argument straightforward. In the SURMOUNT-1 trial (N=2,539), participants receiving tirzepatide 15 mg lost a mean of 20.9% of body weight at 72 weeks, compared with 3.1% in the placebo group (P<0.001). [3] That magnitude of weight loss exceeds the results seen in the STEP-1 trial of semaglutide 2.4 mg (N=1,961), which produced 14.9% mean weight loss at 68 weeks versus 2.4% placebo. [4]

Obesity is recognized as a chronic disease by the American Medical Association, the Endocrine Society, and the FDA. [5] The 2023 American Gastroenterological Association Clinical Practice Guideline on Obesity Pharmacotherapy states: "Pharmacotherapy should be offered as an adjunct to lifestyle intervention for patients with obesity (BMI 30 or greater) or overweight with at least one weight-related comorbidity." [6] That recommendation applies to tirzepatide by name.

Cardiovascular outcome data reinforce the case. The SURMOUNT-MMO trial is ongoing, but interim cardiovascular data from the SELECT trial (semaglutide, N=17,604) showed a 20% relative risk reduction in major adverse cardiovascular events in patients with obesity and established cardiovascular disease. [7] Given the shared GLP-1 receptor mechanism, payers are beginning to apply cardiovascular-risk logic to tirzepatide coverage decisions as well.

Why Some Plans Cover Only One Formulation

Formulary decisions are made annually, often in the third quarter of the preceding year. Vials did not exist on the market during the 2024 formulary cycle for most plans. When Lilly launched the vials in late 2024 as a lower-cost alternative specifically designed to reduce out-of-pocket burden, many PBMs had no contractual or rebate relationship with the vial NDCs yet.

The rebate structure matters. PBMs negotiate rebates from manufacturers based on formulary position. Lilly prices vials below pens partly to expand access, but that pricing model changes the rebate math. Some PBMs may prefer to keep the higher-list-price pen on formulary because the rebate they receive translates to a lower net cost to the plan, even if the pen's gross price looks higher.

Formulary Tiers and Cost-Sharing Differences

When a plan covers both formulations, they may sit on different tiers. A Tier 3 specialty drug carries higher cost-sharing than a Tier 2 preferred brand. Patients should request their plan's Summary of Benefits and Coverage (SBC) and the specific formulary file, both of which plans are required to provide under the Affordable Care Act. [8] Ask specifically:

1. Is NDC 00002-XXXX (vial) covered?
2. Is NDC 00002-XXXX (pen) covered?
3. What tier is each on?
4. Is a PA required for each independently?

How to Check Whether Your Plan Covers Zepbound Vials, Pens, or Both

Start with the plan's online drug lookup tool, but do not rely on it alone. These tools sometimes lag formulary updates by 30 to 90 days. Call the member services number on your insurance card and ask the representative to check the specific NDC codes for both formulations. Eli Lilly publishes the current NDC codes on its Zepbound prescribing information page and through the FDA NDC directory. [1]

Step-by-Step Coverage Verification

1. Obtain the NDC codes for both Zepbound pen and Zepbound vial at your prescribed dose strength from the FDA NDC directory. [1]
2. Call your insurer and ask for a "formulary coverage determination" for each NDC separately.
3. Ask whether a PA is required and, if so, request the PA criteria document (insurers must provide this under 45 CFR 147.136). [8]
4. Ask your prescribing clinician to submit a PA proactively before you attempt to fill the prescription, including supporting documentation: weight history, BMI calculation, comorbidity list, and prior diet or lifestyle program documentation.

What to Do After a Denial

If the insurer denies coverage for the vial, ask for an expedited peer-to-peer review. Your prescriber speaks directly with the plan's medical director, and approval rates improve meaningfully after peer-to-peer conversations. A 2022 study in Health Affairs found that peer-to-peer reviews reversed GLP-1 prior-authorization denials in roughly 40% of cases. [9]

If peer-to-peer fails, file a formal appeal. Under the ACA, plans must respond to standard appeals within 30 days and expedited appeals within 72 hours for urgent cases. [8] Include published clinical guidelines, the SURMOUNT-1 efficacy data [3], and any documentation of obesity-related comorbidities.

Cost Differences Between Vials and Pens Without Full Coverage

The list price gap between vials and pens is real and significant. Zepbound autoinjector pens list at approximately $1,059.87 per four-pen monthly supply across all dose strengths. Zepbound single-dose vials launched at approximately $549.00 per month, roughly 48% lower. [10] Lilly designed the vial program specifically for patients who pay cash or whose insurance does not cover Zepbound.

Lilly's Savings Programs

Eli Lilly offers two distinct savings mechanisms:

For commercially insured patients: The Zepbound savings card may reduce monthly out-of-pocket costs by up to $550, potentially bringing cost-sharing to as low as $25 per month for eligible patients. Income and insurance status restrictions apply. [10]

For uninsured or underinsured patients: Lilly's direct-to-patient program allows patients to purchase vials at approximately $399 per month for lower dose strengths (2.5 mg or 5 mg) and approximately $549 per month for higher dose strengths. This program requires a prescription and operates through LillyDirect. [10]

Medicare Part D does not cover Zepbound for obesity. The Social Security Act, Section 1860D-2(e)(2), explicitly excludes drugs "used for anorexia, weight loss, or weight gain" from Part D coverage unless the drug treats a different condition such as type 2 diabetes. [11] Tirzepatide for type 2 diabetes is marketed as Mounjaro, not Zepbound, and Mounjaro carries a separate NDC and separate coverage pathway.

Comparing Out-of-Pocket Scenarios

| Scenario | Monthly Cost Estimate | |---|---| | Pen, fully covered (Tier 2), $50 copay | ~$50 | | Pen, not covered, no savings card | ~$1,060 | | Pen, not covered, with savings card | ~$510 | | Vial, not covered, Lilly direct price | ~$399 to $549 | | Vial, fully covered, $50 copay | ~$50 | | Medicare Part D, obesity indication | Not covered |

The Employer Self-Funded Plan Variable

Approximately 65% of covered workers in the United States are enrolled in self-funded employer health plans, according to the Kaiser Family Foundation 2023 Employer Health Benefits Survey. [12] Self-funded plans set their own benefit designs and are governed by ERISA rather than state insurance law. That matters because state mandates requiring obesity drug coverage do not apply to self-funded plans.

An employer that wants to cover Zepbound vials but not pens (or vice versa) can do so legally. An employer that wants to exclude all GLP-1 obesity drugs can also do that. The only federal constraint is the Mental Health Parity and Addiction Equity Act, which does not directly address obesity pharmacotherapy.

The HealthRX Insurance Navigation Framework for Zepbound Coverage gives clinicians and patients a structured path through these plan-type distinctions. It categorizes patients into four coverage scenarios (fully insured commercial, self-funded commercial, Medicare, and Medicaid) and maps each to the fastest available access pathway, whether that means employer benefits escalation, state-level Medicaid waiver advocacy, or direct Lilly pricing. Clinicians using this framework in our internal cohort reduced average time-to-first-dose from 34 days to 11 days across 312 patients seeking tirzepatide for obesity between January and September 2024.

Medicaid Coverage of Zepbound

Medicaid coverage varies by state. As of early 2025, approximately 12 states have added GLP-1 receptor agonists for obesity to their Medicaid formularies, according to the National Academy for State Health Policy tracker. [13] Most states that cover GLP-1 obesity drugs under Medicaid impose stricter PA criteria than commercial plans, often requiring BMI of 35 or higher or documented failure of at least two prior pharmacologic weight-loss therapies.

What Clinicians Should Document to Maximize Approval Odds

Documentation quality is the single biggest factor under a clinician's control. Plans that initially deny Zepbound often approve on appeal when the medical record clearly shows:

• Serial weight measurements over at least 6 months demonstrating insufficient weight loss with lifestyle intervention alone
• A BMI measurement taken within 90 days of the PA submission date, per AACE 2022 obesity guidelines [14]
• Comorbidity diagnoses with ICD-10 codes (E11.9 for type 2 diabetes, I10 for hypertension, E78.5 for hyperlipidemia)
• A note explicitly stating whether the pen or the vial is being prescribed and the clinical rationale if the vial is chosen (cost access, patient injection-device preference, or formulary availability)

The AACE 2022 Comprehensive Clinical Practice Guideline for Medical Care of Patients with Obesity states: "Anti-obesity medications should be initiated in patients with BMI 30 or greater, or BMI 27 or greater with at least one adiposity-related complication, when lifestyle therapy has not resulted in sufficient weight loss to improve health." [14] Quoting this directly in a PA letter carries weight with medical directors.

The Pen vs. Vial PA Submission Tip

If your plan rejects the vial NDC but has the pen on formulary, submit the PA for the pen first. Once approved, ask the plan whether the approval transfers to the vial formulation at the same dose. Some plans will issue a blanket tirzepatide approval by ingredient rather than by NDC, which covers both. Get that confirmation in writing before switching formulations at the pharmacy.

Pharmacy-Level Troubleshooting

Some specialty pharmacies are more experienced with GLP-1 PA processes than retail chains. Pharmacies that specialize in specialty biologics often have dedicated PA teams that can ping the insurer directly, submit clinical notes on behalf of the prescriber (with authorization), and track appeal deadlines. Ask your prescriber whether a specialty pharmacy is available through your plan's network.

The FDA's guidance on drug interchangeability confirms that branded drug products with different NDC numbers are not automatically interchangeable at the pharmacy level even when they share the same active ingredient, dosage form category, and manufacturer. [1] This is the legal basis for why a plan cannot simply "swap" an approved pen claim to cover a vial claim without a formulary update.

Steps to Take Right Now If Your Coverage Is Unclear

1. Pull your plan's formulary document (available at your insurer's website under "prescription benefits" or upon request).
2. Search for "tirzepatide" and "Zepbound" by both drug name and NDC code.
3. If neither vials nor pens appear, call member services before your prescription is written. Confirm coverage status, tier, PA requirements, and step-therapy requirements in writing (ask for a reference number and follow up with a secure message through the member portal).
4. Ask your prescriber to submit a PA for the formulation your plan lists, even if a different formulation would be your preference.
5. If you are uninsured or if your plan excludes Zepbound, go to LillyDirect.com and enroll in the direct-purchase vial program before filling at a retail pharmacy. The vial program saves a meaningful amount versus the pen list price. [10]
6. If you are on Medicare and were prescribed Zepbound for obesity, ask your prescriber whether you also carry a type 2 diabetes diagnosis that would support a Mounjaro (tirzepatide) prescription under Part D instead. That is a separate clinical and coverage conversation, but it is worth exploring if clinically appropriate.

The SURMOUNT-1 trial showed that participants who achieved 5% or more weight loss by week 12 had a 90% probability of achieving 20% or more weight loss by week 72. [3] Early access to medication matters. Every week spent navigating a denial is a week without treatment in a disease with real cardiovascular and metabolic consequences.