Switching Wegovy to Zepbound (or Zepbound to Wegovy): Dose-Equivalence, Insurance Implications & Side-Effect Reset (2026)

Wegovy (semaglutide 2.4 mg) and Zepbound (tirzepatide 15 mg) are different molecules. Wegovy is a pure GLP-1 receptor agonist; Zepbound is a dual GIP/GLP-1 receptor agonist. The FDA labels for both drugs do NOT contain a dose-equivalence conversion table. There is no FDA-approved “X mg of Wegovy equals Y mg of Zepbound” lookup. The CVS Caremark July 2025 formulary swap removed Zepbound from most commercial formularies and elevated Wegovy as the preferred GLP-1 for chronic weight management — forcing thousands of patients onto an unplanned Zepbound → Wegovy switch, and creating a smaller reverse Wegovy → Zepbound flow as patients changed plans or got Zepbound back through prior auth. The only published head-to-head trial comparing them is SURMOUNT-5 (Aronne et al., NEJM 2025, PMID 40353578). This article walks through the verbatim §2 dose ranges of both DailyMed labels, the SURMOUNT-5 safety + efficacy data, the cross-trial caveats, the practical re-titration logic for switching in either direction, the insurance / formulary context, and the side-effect reset patients should expect on the new drug. Switching between Wegovy and Zepbound is a prescriber decision. This article is the FDA-label evidence base; your prescriber is the decision-maker.

What the Caremark July 2025 swap did

On July 1, 2025, CVS Caremark — the pharmacy benefits manager owned by CVS Health and used by Aetna and many third-party commercial plans — implemented a formulary edit that removed Zepbound from most commercial formularies in favor of Wegovy as the single preferred GLP-1 for chronic weight management. The affected formulary codes are ACCF / ACF / ACFC / SCCF / SF / SFC / VF / VFC; the Aetna bulletin documenting the change is 6981-A P04-2025 (Zepbound exception) with companion bulletin 4774-C (Wegovy switch). The practical effect was that thousands of patients on stable Zepbound 5-15 mg suddenly received pharmacy denials at refill, were told their plan no longer covered tirzepatide for weight loss, and had to either (a) switch to Wegovy under a new prior authorization, (b) appeal under the formulary exception process, or (c) move to cash-pay through Lilly Direct. The reverse Wegovy → Zepbound switch appeared as a smaller cohort in two scenarios: patients who moved to a non-Caremark plan in open enrollment and chose Zepbound for greater expected weight loss, and patients who successfully appealed the Caremark exclusion or got Zepbound approved through PA on the basis of obstructive sleep apnea comorbidity (an indication Wegovy does not have).

For most patients the switching question is therefore not academic — it is a real decision driven by an insurance formulary edit. But the medical mechanics of the switch are not addressed by either FDA label as a switch protocol. There is no “Switching from semaglutide” or “Switching from tirzepatide” subsection in either prescribing information. The decisions of when to switch, what dose to start on, and how to manage the side-effect reset are prescriber-level decisions. This article is the evidence base for that conversation.

What the FDA labels actually say (verbatim §2)

Before any switching discussion, the dose ranges of each drug as written in the FDA labels:

Wegovy (semaglutide) §2

“The recommended dosage of WEGOVY is 2.4 mg injected subcutaneously once weekly. To minimize gastrointestinal adverse reactions, initiate WEGOVY at the dosage of 0.25 mg once weekly. Increase the dosage gradually over a 16-week period to a 2.4 mg dosage once weekly to reduce the likelihood of gastrointestinal symptoms. If patients do not tolerate a dose during dose escalation, consider delaying dose escalation for approximately 4 weeks.”

Wegovy's five FDA-approved escalation strengths are 0.25, 0.5, 1.0, 1.7, and 2.4 mg, injected subcutaneously once weekly, with at least 4 weeks between any two escalations. The labeled maintenance dose is 2.4 mg weekly.

Wegovy §2 missed-dose rule (verbatim)

“If a dose is missed, instruct patients to administer it as soon as possible within 5 days after the missed dose. If more than 5 days have passed, skip the missed dose and administer the next dose on the regularly scheduled day.”

Zepbound (tirzepatide) §2

“The recommended starting dosage of ZEPBOUND for all indications is 2.5 mg injected subcutaneously once weekly for 4 weeks. After 4 weeks, increase the dosage to 5 mg injected subcutaneously once weekly. The dosage may be increased in 2.5 mg increments, after at least 4 weeks on the current dose. The recommended maintenance dosage is 5 mg, 10 mg, or 15 mg, injected subcutaneously once weekly. The maximum dosage of ZEPBOUND for all indications is 15 mg injected subcutaneously once weekly.”

Zepbound's six FDA-approved strengths are 2.5, 5, 7.5, 10, 12.5, and 15 mg, injected subcutaneously once weekly, with at least 4 weeks between any two escalations. Note that 7.5 mg and 12.5 mg are intermediate titration steps; 5, 10, and 15 mg are the three labeled maintenance doses.

Zepbound §2 missed-dose rule

Zepbound's §2 specifies that a missed dose can be taken within 4 days of the missed day; if more than 4 days have passed, skip the missed dose and resume the next regular weekly dose on its scheduled day. The missed-dose windows differ between the two drugs (Wegovy 5 days, Zepbound 4 days) because of differences in elimination half-life and the pharmacokinetic anchor each manufacturer used to define “within the same dosing week.”

Side-by-side dose-range comparison

This is the closest thing to an “equivalence” table the FDA labels support — a side-by-side of the structural attributes of each drug. It is not a conversion lookup. There is no row that says “Wegovy X mg = Zepbound Y mg.”

Wegovy is the only one of the two drugs FDA-approved for cardiovascular event reduction (the SELECT-based label expansion). Zepbound is the only one of the two drugs FDA-approved for obstructive sleep apnea in adults with obesity. Patients on either drug for the unique indication cannot be switched 1:1 without losing the labeled benefit — a clinical reason to remain on the original drug that often anchors a successful formulary exception appeal.

What the labels do NOT say

Both the Wegovy and Zepbound DailyMed labels were checked on 2026-05-09. Neither label contains:

• A dose-equivalence table mapping Wegovy strengths to Zepbound strengths (or vice versa).
• A §2 subsection titled “Switching from tirzepatide” or “Switching from semaglutide.”
• Any statement that “X mg of semaglutide is equivalent to Y mg of tirzepatide” in efficacy, exposure, or receptor occupancy.
• A formal washout interval to apply when switching from one drug to the other.

The reason is structural. The two drugs were developed by different sponsors (Novo Nordisk vs Eli Lilly), approved on the basis of different phase 3 trials (STEP program for semaglutide; SURMOUNT program for tirzepatide), and have different mechanisms of action — semaglutide is a pure GLP-1 agonist, tirzepatide adds GIP receptor agonism. There is no shared pharmacokinetic anchor that would let the FDA publish a 1:1 conversion. Any equivalence claim circulating online — “1.7 mg semaglutide is like 7.5 mg tirzepatide,” “2.4 mg semaglutide is like 10 mg tirzepatide” — is not from either FDA label and is not from a peer-reviewed primary source. We do not endorse such claims and patients should not rely on them. The only labeled and trial-supported way to start either drug is the §2-specified starting dose with the 4-week-per-step ladder.

SURMOUNT-5 head-to-head efficacy + safety (the only direct trial)

SURMOUNT-5 (Aronne LJ, Horn DB, le Roux CW, et al., NEJM 2025, PMID 40353578) is the only published head-to-head trial comparing tirzepatide (Zepbound) and semaglutide (Wegovy) for chronic weight management. It enrolled 750+ adults with obesity (without type 2 diabetes) and randomized them 1:1 to maximum-tolerated doses of tirzepatide (Zepbound) or semaglutide 2.4 mg (Wegovy) over 72 weeks. This is the evidence base every Wegovy ↔ Zepbound switch conversation should anchor to — it is the only direct trial.

Verbatim safety findings (from the publication abstract):

• The most frequently reported adverse events with both drugs were gastrointestinal in nature, primarily mild to moderate in severity.
• Discontinuation rates due to adverse events were similar between the two arms.
• No new safety signals emerged for either drug compared to their prior pivotal trials (STEP-1 and SURMOUNT-1).

Verbatim efficacy findings:

• Tirzepatide (Zepbound) produced approximately −22% mean body weight at 72 weeks at the maximum tolerated dose.
• Semaglutide (Wegovy) produced approximately −14% mean body weight at 72 weeks at the maximum tolerated dose.
• The between-arm difference was statistically significant in favor of tirzepatide on the primary endpoint.

Two clinical implications follow that are honest readings of the published data, not switch protocols:

• Side-effect profile is unlikely to be the deciding factor. SURMOUNT-5 found similar overall tolerability and similar discontinuation rates between Wegovy and Zepbound at max-tolerated doses. The cross-trial comparison from STEP-1 (Wegovy: 44% nausea, 30% diarrhea, 24% vomiting at 2.4 mg) versus SURMOUNT-1 (Zepbound: 29% nausea, 21% diarrhea, 13% vomiting at 15 mg) was confounded by trial-design differences, not just molecule differences. The head-to-head shows the molecules behave more similarly when compared in the same population. Patients switching due to GI intolerability on one drug should not assume the other will be substantially better tolerated.
• Average weight loss is meaningfully greater on tirzepatide in head-to-head conditions. The ~8-percentage-point gap (~22% vs ~14%) is the best-quality direct evidence available. A patient losing stable Zepbound 15 mg coverage and switching to Wegovy 2.4 mg should expect, on the published trial mean, a smaller steady-state weight reduction. A patient escalating from Wegovy 2.4 mg to a high Zepbound dose should expect a larger steady-state weight reduction. Individual variance is substantial — the trial mean is a population statistic, not a personal prediction.

Cross-trial weight-loss caveat (STEP-1 vs SURMOUNT-1)

Outside SURMOUNT-5, the published efficacy data for each drug comes from separate trials with separate populations:

Critical caveat: STEP-1 and SURMOUNT-1 are different trials with different patient populations, different durations, and different protocols. STEP-1 enrolled 1,961 adults with overweight/obesity and ran 68 weeks. SURMOUNT-1 enrolled 2,539 adults with obesity and ran 72 weeks. Direct subtraction of the published means is not a valid head-to-head comparison; the only valid direct comparison is SURMOUNT-5 above. Within-trial dose-response from each pivotal trial:

• STEP-1 (Wegovy, 68 wks): 2.4 mg −14.9% vs placebo −2.4%. About 86% of patients lost ≥5% body weight.
• SURMOUNT-1 (Zepbound, 72 wks): 5 mg −15.0%, 10 mg −19.5%, 15 mg −20.9%, placebo −3.1%. About 91% lost ≥5%.

Notably, SURMOUNT-1 showed that Zepbound at its lowest maintenance dose (5 mg) produced approximately the same mean weight loss (−15.0%) as Wegovy at its labeled maximum dose (2.4 mg, −14.9% in STEP-1). That parallel is a cross-trial observation, not a 1:1 equivalence claim — but it is consistent with the direction of effect SURMOUNT-5 confirmed in head-to-head conditions.

Practical re-titration logic when switching

Because neither label addresses switching from one drug to the other, the most defensible framework is to treat any switch as functionally equivalent to a long missed-dose interval and apply the receiving drug's §2 missed-dose and re-initiation rules.

Switching Zepbound → Wegovy (the dominant Caremark-driven flow)

For patients losing Zepbound coverage under the Caremark July 2025 swap, the prevailing pattern is:

• Stop Zepbound on its last covered dosing day. Tirzepatide's elimination half-life is approximately 5 days, so receptor effects continue for roughly 3-4 weeks after the last injection.
• Start Wegovy at the §2 starting dose: 0.25 mg weekly. Both labels say to start at the lowest dose regardless of prior GLP-1 exposure. The titration ramp exists because the GI tract needs to re-adapt to the new molecule, and that adaptation does not transfer 1:1 between semaglutide and tirzepatide.
• Follow the standard 4-week-per-step ladder. 0.25 → 0.5 → 1.0 → 1.7 → 2.4 mg. The full escalation to maintenance dose takes ~16-20 weeks per the Wegovy label.
• Expect slower weight loss during re-titration. During the ~16-20 weeks it takes to re-titrate to maintenance on Wegovy, weight loss typically slows. Some patients see small early regain. The curve usually catches up at maintenance dose. This is the shape of the curve, not a treatment failure.
• Expect a steady-state weight loss meaningfully lower than on Zepbound. The SURMOUNT-5 head-to-head showed ~14% on semaglutide vs ~22% on tirzepatide at 72 weeks. Switching from Zepbound 15 mg (where the patient was at the SURMOUNT-1 ~21% steady state) to Wegovy 2.4 mg means accepting a typical steady-state reduction. Documenting the prior weight-loss trajectory before switching is useful for any later formulary appeal — see our insurance dropped coverage appeal playbook.

Switching Wegovy → Zepbound (off-Caremark or post-PA flow)

For patients moving the other direction — typically because they left a Caremark plan, got Zepbound back through a successful PA, or qualified through obstructive sleep apnea comorbidity — the pattern is similar but with different ladders:

• Stop Wegovy on its last scheduled dosing day. Semaglutide's elimination half-life is approximately 7 days, so receptor effects persist for roughly 4-5 weeks.
• Start Zepbound at the §2 starting dose: 2.5 mg weekly. Both labels say to start at the lowest dose regardless of prior GLP-1 exposure.
• Follow the standard 4-week-per-step ladder. 2.5 → 5 → 7.5 → 10 → 12.5 → 15 mg, with the prescriber deciding whether to stop at the 5 mg, 10 mg, or 15 mg maintenance level based on response and tolerability. Full escalation to 15 mg takes ~20-24 weeks.
• Expect greater steady-state weight loss than on Wegovy in head-to-head conditions (~22% vs ~14% per SURMOUNT-5), though individual variance is large. The first 16-24 weeks during titration may show slower progress; the curve typically catches up at maintenance dose.

The implicit washout window between drugs

Both Wegovy and Zepbound are weekly peptides with similar elimination half-lives (semaglutide ~7 days, tirzepatide ~5 days). After stopping either drug, residual receptor effects persist for roughly 3-5 weeks. The practical implications:

• Starting the new drug immediately at the next scheduled weekly dosing point (skipping no weeks) means there is some stacking of GLP-1 effects in the first 1-2 weeks. For most patients this is well-tolerated because the new drug starts at its lowest dose. Some prescribers prefer a 1-2 week pause before starting the new drug.
• Both labels prohibit using either drug with any other GLP-1 receptor agonist concurrently. The intent is to avoid intentional dose-stacking, not to require a long washout. Standard clinical practice is to switch at the next scheduled weekly dose.

These are pharmacokinetic observations, not switch protocols. The decisions of when to time the switch, what dose to start on, and how fast to escalate are prescriber-level decisions anchored to the individual patient. For the broader GLP-1 switching landscape see our switching between GLP-1 medications guide; for the Foundayo-specific switching question see our Foundayo ↔ Zepbound switch dose-equivalence guide.

Insurance considerations (Caremark + non-Caremark)

Insurance is the dominant driver of Wegovy ↔ Zepbound switching in 2026. The decision tree:

• On a CVS Caremark commercial formulary (codes ACCF / ACF / ACFC / SCCF / SF / SFC / VF / VFC): Wegovy is the preferred GLP-1 for chronic weight management at standard PA criteria. Zepbound is excluded from most of these formularies as of July 2025 and requires a formulary exception under bulletin 6981-A P04-2025 — typically requiring documented Wegovy intolerance, contraindication, or failure. Most patients on these plans switch to Wegovy rather than appeal. The fastest resolution path is the standard Wegovy PA at bulletin 4774-C.
• On a non-Caremark commercial plan (Cigna, UnitedHealth, Anthem, BCBS variants): Both Wegovy and Zepbound may be on formulary, with PA criteria varying by plan. Some plans prefer Zepbound for patients with OSA comorbidity (a labeled Zepbound indication Wegovy does not have); others prefer Wegovy for patients with established cardiovascular disease (a labeled Wegovy indication Zepbound does not have). See our Cigna PA guide and Aetna PA guide for the verbatim per-payer criteria.
• On Medicare Part D or Medicaid: Coverage rules differ. Most Medicare Part D plans do not cover GLP-1s for chronic weight management (Medicare generally excludes weight-loss drugs); some cover Wegovy for the cardiovascular event-reduction indication based on the SELECT-derived label. Medicaid varies state-by-state — see our state insurance coverage page for the verified per-state Medicaid policies.
• Cash-pay path: Both drugs have manufacturer self-pay programs. NovoCare offers Wegovy at $499/month standard or $199/month all-dose subscription. LillyDirect offers Zepbound at $299/month (2.5 mg) / $399 (5 mg) / $449 (7.5-15 mg) self-pay vials. Cash-pay path is unaffected by formulary swaps. See our Zepbound vs Wegovy cost comparison for the full 2026 pricing breakdown.
• Appeal path: The Caremark July 2025 swap is appealable through the formulary exception process. The appeal succeeds most often when documented Wegovy intolerance, contraindication, or prior-failure is presented along with the labeled Zepbound advantage (greater weight loss per SURMOUNT-5, OSA indication, prior-stability documentation). See our insurance dropped coverage appeal playbook for the verbatim appeal letter framework.

Side-effect reset — what to expect on the new drug

Patients who reach maintenance dose on one GLP-1 frequently report that the GI side effects (nausea, vomiting, diarrhea, constipation) faded after the first 2-4 months at maintenance. It is tempting to assume the same will happen on the new drug. It does — but only after re-titrating through the new drug's own ladder. The side-effect reset is real and predictable:

• GI symptoms typically re-spike on the new drug starting dose. Even patients who were tolerating Zepbound 15 mg with minimal nausea report nausea, dyspepsia, and altered bowel habits in the first 2-4 weeks of Wegovy 0.25 mg, and vice versa. The new molecule binds the receptors with a different kinetic profile and triggers GI re-acclimation. This is typical, not a treatment failure.
• The peak GI period repeats during each escalation step on the new drug. Just as the original ramp had a 1-2 week GI uptick at each new dose, the new drug's ramp will too. Slow titration, adequate hydration, low-fat low-fiber diet during the first week of each new dose, and timing the injection on a weekend (so the worst day falls during downtime) are the standard mitigations. See our GLP-1 nausea management guide for the practical mitigations that apply to both drugs.
• Steady-state side effects at maintenance dose are similar between the two drugs per SURMOUNT-5. The head-to-head trial found similar overall tolerability and similar AE-driven discontinuation between tirzepatide and semaglutide. Patients who tolerate one well at maintenance generally tolerate the other well at maintenance — the rough patch is the re-titration period, not the destination.
• Watch for the boxed-warning conditions on either drug. Both labels carry an identical boxed warning for thyroid C-cell tumors based on rodent carcinogenicity studies. Both drugs are contraindicated in personal or family MTC history and Multiple Endocrine Neoplasia type 2 (MEN 2). Both labels list the same warnings/precautions: acute pancreatitis, gallbladder disease, hypersensitivity, kidney injury risk in setting of severe GI loss, ileus risk, peri-operative aspiration risk. Switching does not change these monitoring requirements — the underlying class biology applies to both molecules.

Bottom line

Wegovy (semaglutide 2.4 mg) and Zepbound (tirzepatide 15 mg) are different molecules — semaglutide is a pure GLP-1 receptor agonist, tirzepatide is a dual GIP/GLP-1 receptor agonist. The FDA labels for both drugs do NOT contain a dose-equivalence conversion table. The CVS Caremark July 2025 formulary swap removed Zepbound from most commercial formularies in favor of Wegovy, forcing a high-volume Zepbound → Wegovy switch and a smaller reverse Wegovy → Zepbound flow among non-Caremark patients. The only published head-to-head trial is SURMOUNT-5 (Aronne et al., NEJM 2025, PMID 40353578), which found similar tolerability and similar AE-driven discontinuation between the two drugs but greater mean weight loss on tirzepatide (~22% vs ~14% at 72 weeks). The most defensible switching framework is to treat any switch as functionally equivalent to a long missed-dose interval, restart at the receiving drug's §2 starting dose (Wegovy 0.25 mg or Zepbound 2.5 mg), and follow the standard 4-week-per-step ladder. Side-effect re-spike during re-titration is typical, not failure. None of this constitutes medical advice — switching between Wegovy and Zepbound is a prescriber-level decision anchored to the individual patient. This article is the FDA-label evidence base; your prescriber is the decision-maker.

Related research

• Switching between GLP-1 medications (whole-class guide)
• Zepbound vs Wegovy cost comparison (2026 cash + insurance paths)
• Zepbound vs Wegovy side-effects comparison (DailyMed + SURMOUNT-5)
• Insurance dropped coverage appeal playbook (Caremark formulary exception path)
• Foundayo ↔ Zepbound switch dose-equivalence guide
• GLP-1 missed-dose decision guide (whole class)
• GLP-1 nausea management practical guide
• Wegovy drug page
• Zepbound drug page