Stopping & switching

Switching From Wegovy to Zepbound: What to Know

There is no FDA-approved dose conversion between semaglutide and tirzepatide. Here is what the labels actually say, what published switching data shows, and the questions worth asking before your first Zepbound dose.

Last verified September 14, 2026·11 sources cited·Wegovy Zepbound

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People switch for four main reasons: the weight loss stalled, the side effects were too much, the insurance changed, or the price moved. All four are common, and switching between GLP-1 drugs is routine - in one analysis of 42,423 patients with more than one GLP-1 prescription, 29.7% switched agents at least once and 14.3% switched twice or more [1].

What is not routine is having a rulebook. Wegovy is semaglutide, a GLP-1 receptor agonist. Zepbound is tirzepatide, which hits both the GLP-1 receptor and the GIP receptor. They are different molecules with different receptor profiles, and no regulator has published a way to convert a dose of one into a dose of the other.

This article explains what the labels do say, what published evidence exists, and what to bring to the conversation. Every dosing passage summarizes the FDA-approved prescribing information and Instructions for Use for these products; it is not medical advice and it does not tell you what dose to take. Dose selection and switch timing are a prescriber’s job, and you should follow the prescription you are given.

Is there a dose conversion chart?

No FDA-endorsed one, and here is why that matters more than it sounds.

The Zepbound prescribing information, revised August 2026, sets one starting dosage for everyone: 2.5 mg once weekly for four weeks, for all indications. The label then adds, in its own words, that “the 2.5 mg dosage is for treatment initiation and is not approved as a maintenance dosage” [2]. After four weeks the dose increases to 5 mg, and may then be increased in 2.5 mg increments after at least four weeks on the current dose, up to a maximum of 15 mg. Recommended maintenance dosages are 5 mg, 10 mg or 15 mg for weight reduction [2].

Nowhere does that label carve out an exception for people coming off another GLP-1. There is no “if the patient was on semaglutide 2.4 mg, start at X.”

Conversion tables do circulate, and the most widely cited legitimate one is the Beth Israel Lahey Health GLP-1 RA Conversion Guide, adapted from Whitley et al. in Clinical Diabetes (2023). It is worth reading what that document says about itself:

“Assessment of equivalent dose is based on head-to-head clinical trials, when available, and/or clinical experience. This guide does not replace clinical judgment. The conversion chart is based on the relative effect on A1c and does not address the potential for side effects. If the patient experienced GI side effects on GLP-1RAs in the past, consider stepping down a dose when converting agents. Due to the risk for side effects, do not switch from a submaximal dose of one agent to the maximum dose of another.” [3]

Three things in that paragraph deserve emphasis. The table is built on A1c effect, not weight loss. It does not address side effects. And it explicitly warns against a jump from a submaximal dose of one drug to a maximum dose of another - which is exactly the move a naive “conversion chart” invites.

The only place the FDA has spelled out a switching path in this class is within the same molecule: the Wegovy label tells you how to move between Wegovy injection and Wegovy 25 mg tablets, starting the tablets one week after the last 2.4 mg injection, or starting the 2.4 mg injection the day after the last tablet [4]. That is the shape of an official conversion. Nothing like it exists between semaglutide and tirzepatide.

What about “equivalence” research?

There is a serious modeling attempt. A 2026 analysis pooled arm-level data from 48 treatment arms across the SUSTAIN, STEP, SURPASS and SURMOUNT-2 programs in type 2 diabetes (16,524 participants) and used Bayesian hierarchical spline models to estimate the probability that different dose pairs produce equivalent weight change within ±2 percentage points. It found high probabilities of equivalence for semaglutide 2.4 mg versus tirzepatide 10 mg (99.4%) and semaglutide 7.2 mg versus tirzepatide 15 mg (94.8%), while lower semaglutide doses were not equivalent to higher tirzepatide doses [5].

One limit deserves more weight than it usually gets in coverage of this paper: the analysis was restricted to trials in people with type 2 diabetes, and trials enrolling only people without diabetes were explicitly excluded. Since Wegovy and Zepbound are the weight-management labels, the population the model was fitted on is not the population most readers of this article belong to. It is genuinely useful for understanding where the two drugs land relative to each other after months of titration. It is not a starting-dose instruction, and the authors do not present it as one. The paper’s own framing is that equivalence is driven by dose rather than drug identity, and that the model gives a quantitative framework for individualized decisions when direct comparative evidence is missing.

The practical question when switching is not “what is my equivalent dose?” It is “what is a safe dose to start at, given how I tolerated the last drug?”

How long do I wait between the last Wegovy dose and the first Zepbound dose?

No label specifies a washout period. What both labels do state is that concomitant use of the two is not recommended.

The Zepbound label, under Limitations of Use: “Coadministration with other tirzepatide-containing products or with any glucagon-like peptide-1 (GLP-1) receptor agonist is not recommended” [2]. The Wegovy label says the same in reverse: concomitant use with other semaglutide-containing products or any other GLP-1 receptor agonist is not recommended [4].

That rules out finishing your last Wegovy pen while starting Zepbound, or doubling up “to be safe.”

Semaglutide has a half-life of about one week, so it clears over roughly five weeks. That means there is always some pharmacological overlap when you switch on a normal weekly schedule - which is expected, and is not what the label is warning about.

A 2026 Pharmaceutical Journal learning article for pharmacists, written for the reverse switch (tirzepatide to semaglutide), lays out the options clinicians choose between: a one-to-two-week washout, preferred for patients who had significant side effects, or a same-day switch starting the new drug on the next scheduled dose day, considered for stable patients who were tolerating treatment well and where the clinician judges the risk low. It adds that a washout should also be considered when moving from an injection to an oral, that any choice should be thoughtfully justified and documented, and that follow-up should happen at two to four weeks [6].

Your prescriber sets the timing. If you are given a date, it is reasonable to ask what it is based on.

What does the evidence say about how a switch actually goes?

Thinner than you would hope, but not empty.

The prospective switching study. The only prospective study of the first 12 weeks after switching directly to tirzepatide 5 mg - skipping the 2.5 mg initiation dose - enrolled people with type 2 diabetes who had been on a stable GLP-1 dose for at least three months (semaglutide 0.5, 1 or 2 mg; dulaglutide 0.75 to 4.5 mg; or liraglutide 1.2 to 1.8 mg). At week 12, mean HbA1c fell 0.43%, fasting serum glucose fell 7.83 mg/dL and weight fell 2.15 kg. Twenty participants (13.2%) developed gastrointestinal events and three (2%) stopped tirzepatide for adverse events. There were no severe hypoglycemic events or deaths [7].

Two caveats: this was a diabetes population, not a weight-management population, and it was single-arm over 12 weeks. But it is the closest thing to a controlled look at a direct switch, and the headline is that it went reasonably.

Real-world data in people who are already weight-reduced. A Weill Cornell retrospective cohort published in Obesity in 2026 looked specifically at six-month tirzepatide outcomes in adults who had already lost at least 10% of body weight before starting it, including those switching from therapeutic-dose semaglutide (at least 1.7 mg weekly for at least a month), and split switchers by whether the reason was non-response or something else [8]. This is one of the very few published data sets that addresses what people actually want to know: if I already lost weight on Wegovy, what does Zepbound add?

Switchers can respond more slowly at first. An Italian real-world cohort of 248 adults on semaglutide found that switchers - people previously on liraglutide, 24% of the cohort - had a reduced early anthropometric response compared with treatment-naive patients, though one-year outcomes were similar. The authors attribute the early gap partly to dose and argue for dose optimization to avoid suboptimal initial results after a switch [9]. That is a different pair of drugs, but the pattern is worth knowing: a slow first two months after a switch is not necessarily a sign the new drug will not work.

What should I expect in the first few weeks?

Honest answer: probably some backsliding on appetite control, and possibly some gastrointestinal symptoms.

If you were on Wegovy 2.4 mg and start Zepbound at 2.5 mg, you are moving from a maintenance dose to an initiation dose. The Zepbound label is explicit that 2.5 mg is not a maintenance dose [2]. Appetite suppression during that window may be noticeably weaker than what you were used to, and it takes at least eight weeks to reach 5 mg and longer to reach a full maintenance dose.

On the side-effect front, gastrointestinal events in tirzepatide trials occurred primarily during dose escalation, and the Zepbound label reflects that in its escalation schedule [2]. The BILH guidance suggests stepping down a dose when converting for patients who had gastrointestinal side effects before [3].

Weight may plateau or tick up briefly during the transition. That is consistent with what the switching literature shows and is not evidence the new drug is failing.

What do the labels say about missed doses and dose-day changes?

What follows summarizes the FDA-approved prescribing information and Instructions for Use for each product. It is a description of the labels, not instructions for any individual - follow the prescription you were given and the directions from your own prescriber and pharmacist. The two drugs describe different rules.

Zepbound. The label states that if a dose is missed, it should be administered as soon as possible within four days (96 hours) after the missed dose; if more than four days have passed, the missed dose is skipped and the next dose is given on the regularly scheduled day. It adds that the day of weekly administration can be changed, if necessary, as long as the time between the two doses is at least three days (72 hours) [2][10].

Wegovy. The label states that if one dose is missed and the next scheduled dose is more than two days away, the dose should be administered as soon as possible; if the next scheduled dose is less than two days away, that dose is not administered and dosing resumes on the regularly scheduled day. And notably, the current label states that if two or more consecutive doses are missed, prescribers should “reinitiate dosage escalation at a lower dosage to reduce the risk of gastrointestinal adverse reactions” - a dose-escalation decision that belongs to the prescriber, not the patient [4].

If you are switching because of a coverage gap and might go weeks without either drug, flag that to your prescriber. Gastrointestinal tolerance fades, and restarting at a previously tolerated dose after a long break has landed people in hospital - there is a published case report of exactly that after a five-week pause [11].

Will insurance be the thing that decides this?

The biggest forced switch in this class ran in the other direction. Effective July 1, 2025, CVS Caremark removed Zepbound from its standard, advanced control and value commercial template formularies and made Wegovy the preferred weight-management GLP-1, affecting roughly 30% of the people it covers [12]. After the change, more than 95% of prescriptions filled by affected members were for Wegovy, compared with a roughly even split before.

Some useful details from how that was handled:

Existing prior authorizations transferred. Members with an active Zepbound prior authorization did not need a new one to move to Wegovy; overrides were transitioned so access was not interrupted [12].
A formulary exception process existed for members who had already tried Wegovy and had severe or intolerable side effects or insufficient weight loss, with a case-by-case medical necessity review requiring supporting documentation from the prescriber [12].
The plan sponsor’s own guidance said the starting dose varies. In its member FAQ, the Massachusetts Group Insurance Commission wrote that the appropriate Wegovy dose when transitioning from Zepbound “depends on where the member is in their treatment journey,” that both drugs require titration, and that the choice of dose is up to the provider because “clinical data on direct transitions is limited” [12].

Then it reversed. CVS Health announced on May 28, 2026 that Caremark would add Zepbound back to its most common commercial formularies “as an additional preferred option,” effective October 1, 2026, for plan sponsors that elect to cover weight-management medications; the same announcement removed the new-to-market block on Foundayo (orforglipron) effective June 1, 2026, and said Wegovy injection and pill would retain preferred status [13]. CVS did not publish tier placement or member copay amounts for either product, and those are set by each plan sponsor rather than by the formulary listing - so check your own plan documents rather than assuming the two will cost the same.

The lesson for anyone switching for coverage reasons: formularies change in both directions, and they change on quarterly cycles. Ask what your plan’s formulary looks like for the coming plan year before you rebuild your whole regimen around it.

What should I bring to the appointment?

A prescriber choosing your starting dose is essentially reading your tolerance history. Make that easy:

Your current Wegovy dose and how long you have been on it.
How each step up went. “I was fine at 1 mg but had two rough weeks at 1.7 mg” is exactly the information that shapes the answer.
The date of your last injection.
Your weight trend over the last three months, including any plateau.
Why you want to switch - stalled loss, side effects, cost, coverage. The reason changes the plan.
Insurance details: whether Zepbound is on formulary, what tier, and any prior authorization or denial letters.

Reasonable questions to ask: Is this starting dose based on the label or on your judgment for my case? How long before I am at a maintenance dose? What should I do if appetite comes roaring back at 2.5 mg? When do we check in?

What is the bottom line?

Switching from Wegovy to Zepbound is common and generally straightforward, but it is not a swap - it is a restart on a different molecule with its own escalation schedule. The label starts everyone at 2.5 mg. No validated milligram conversion exists, and any chart offering one clean number is offering clinical judgment dressed up as a rule. Do not overlap the two drugs. Expect a transition window where appetite control is weaker. And if a coverage change is driving the switch, sort the paperwork before your last pen runs out.

Sources

Questions people ask

Is there a dose conversion chart from Wegovy to Zepbound?

No FDA-endorsed conversion exists. The Zepbound label sets a single starting dosage of 2.5 mg once weekly for four weeks for all indications, and states that 2.5 mg is for treatment initiation and is not approved as a maintenance dosage. Published conversion tables are based on effect on A1c in diabetes trials, not on weight loss, and their authors say they do not replace clinical judgment.

Do I have to restart at the lowest Zepbound dose?

The label's escalation schedule starts everyone at 2.5 mg. Whether a prescriber starts a person higher based on prior GLP-1 tolerance is a clinical decision, not a labeled instruction. The published health-system conversion guidance warns against jumping from a submaximal dose of one agent to the maximum dose of another.

How long should I wait between my last Wegovy dose and my first Zepbound dose?

No label sets a washout. Both labels do say not to use two GLP-1 products at the same time. Semaglutide has a half-life of about a week, so drug levels fall gradually. Pharmacy guidance describes both a short washout and a same-day switch as options depending on the person, and says the choice should be documented. Your prescriber sets the timing.

Can I take Wegovy and Zepbound at the same time?

No. The Zepbound label states that coadministration with other tirzepatide-containing products or with any GLP-1 receptor agonist is not recommended, and the Wegovy label carries the mirror-image statement.

Will I lose more weight on Zepbound?

In the SURMOUNT-5 head-to-head trial, tirzepatide produced greater average weight loss than semaglutide. Individual response varies, and a 2026 model-based analysis in Diabetes Therapy estimated high probabilities of weight-loss equivalence at specific dose pairs, such as semaglutide 2.4 mg versus tirzepatide 10 mg (99.4%). That analysis was fitted only on trials in people with type 2 diabetes, and it is a model of trial averages, not a dosing rule.

Will my side effects be the same?

Both drugs cause mostly mild-to-moderate gastrointestinal effects that cluster around dose increases. In a prospective study of people with type 2 diabetes switching directly to tirzepatide 5 mg, 13.2% had gastrointestinal events over 12 weeks and 2% stopped for adverse events.

Do I need a new prior authorization?

It depends on the plan. When CVS Caremark switched members from Zepbound to Wegovy in 2025, existing prior authorizations were transitioned so members did not have to repeat the process. Check with the plan before assuming either way.

What should I bring to the appointment?

Your current dose, how long you have been on it, how you tolerated each step up, the date of your last injection, your weight trend, and any prior authorization or denial letters. A prescriber choosing a starting dose is working from your tolerance history.

This article summarizes FDA labeling, published research and company information current as of September 14, 2026. It is not medical advice and does not replace a conversation with your own healthcare provider. How we research and verify.