Switching from Ozempic or Wegovy to Mounjaro or Zepbound: what do the US labels say?

Is it a switch if the brand changes but the medicine doesn’t?

Partly. The medicine stays the same, but each brand has its own doses and approved uses, so a prescriber still sets the dose. The medicine is what works in your body; the brand is the name on the box. Mounjaro and Zepbound are both tirzepatide, and Ozempic and Wegovy are both semaglutide.^1,2,3

Think of acetaminophen. It is the medicine; Tylenol is one brand of it. GLP‑1 medicines work the same way, with one medicine sold under several brands for different uses:

Source: FDA approved-drug records and the US labels, checked Oct 14, 2026.⁹

Brands of the same medicine can still have different doses and approved uses. Our Mounjaro vs Zepbound and Ozempic vs Wegovy pages explain those differences.

Why do people switch GLP‑1 medicines?

Usually for side effects, results, cost or coverage. US guidance expects that some people will need a different medicine.^6,7

• Results: NIH says that when weight loss falls short, a clinician may “consider using a different weight management medication”.⁶
• Guidelines: the American Diabetes Association’s 2026 standards added “considering alternative pharmacologic agents” when treatment needs changing.⁷
• Side effects: the Wegovy label tells prescribers to consider the Wegovy injection for people who don’t tolerate the Wegovy tablets.²
• Coverage: plans and programs cover some products and not others. Medicare’s GLP‑1 Bridge, for example, covers the Zepbound KwikPen but not Zepbound single-dose pens or vials.¹⁰

If your weight has stalled, our plateau post covers the other options NIH lists.

What do the US labels say about switching?

The labels say not to combine GLP‑1 medicines. They describe switching only between forms of semaglutide, not between different medicines.^1,2,3,4

Never two at once

The Zepbound label says use with any other GLP‑1 medicine “is not recommended.”¹ The Wegovy, Foundayo and Saxenda labels say the same about their own medicines.^2,4,5

Switches the labels do describe

These are instructions to prescribers, within one medicine. They show the doses of two forms don’t match milligram for milligram; they are not a guide to change doses yourself.

• Wegovy injection to Wegovy tablets: people on the 2.4 mg injection may move to the 25 mg tablet, starting one week after the last injection.²
• Wegovy tablets to Wegovy injection: the injection starts the day after the last tablet.²
• Rybelsus and Ozempic tablets: the label says they are “not substitutable on a mg-to-mg basis” and gives its own switching steps. It also describes moving from one Ozempic injection dose to tablets.³

Switches the labels don’t describe

We found no instructions for moving between different medicines, such as semaglutide to tirzepatide, in the Zepbound, Mounjaro, Wegovy, Ozempic, Rybelsus, Foundayo or Saxenda labels.^1,2,3,4,5,11 Each label gives only its own starting dose:

• Zepbound: 2.5 mg once a week for 4 weeks. The label says this dose “is for treatment initiation and is not approved as a maintenance dosage.”¹
• Wegovy injection: 0.25 mg once a week for weeks 1 to 4.²
• Foundayo: 0.8 mg once a day for at least 30 days.⁴

None of these labels says whether someone coming from another GLP‑1 should start at that dose or higher. That decision is left to the prescriber.

Why don’t we publish a dose conversion chart?

Because no US label or the ADA’s 2026 standards that we read gives one between different medicines. A chart would be our guess, not a source.^1,2,3,4,7

Even two tablets of the same medicine can’t be swapped milligram for milligram. The label says Rybelsus and Ozempic tablets are “not substitutable on a mg-to-mg basis.”³ Semaglutide, tirzepatide and orforglipron are different molecules, tested in separate trials.

The ADA’s 2026 standards say each person’s dose and step-up should balance “efficacy, benefits, and tolerability.”⁷ Searches for a “Wegovy to Zepbound dosage chart” are common. If you find one, ask your prescriber where it came from.

How long does the old medicine stay in your body?

Semaglutide lingers longest. Its half-life is about 1 week, so it stays in the blood 5 to 7 weeks after the last Wegovy dose. Tirzepatide’s half-life is about 5 days.^1,2

Half-life means the time it takes for half of the medicine to leave your blood. Here is what the labels give:

• Semaglutide (Wegovy, Ozempic, Rybelsus): about 1 week.^2,3
• Tirzepatide (Zepbound, Mounjaro): about 5 days.^1,11
• Orforglipron (Foundayo): about 29 to 49 hours.⁴
• Liraglutide (Saxenda): about 13 hours.⁵

This is why weekly medicines can still be working after you stop them. The labels set no waiting time between two different medicines. Ask how long to leave between your last old dose and your first new one.

Gaps matter too. If a switch is delayed, for example while insurance approves it, the missed-dose rules apply:

• Wegovy injection: after 2 or more missed doses in a row, the label says to restart the step-up at a lower dose.²
• Zepbound: a missed dose can be taken within 4 days; after that, skip it.¹
• Foundayo: after 7 or more missed doses in a row, restart the step-up at a lower dose.⁴

Will side effects come back after a switch?

They can. Stomach side effects are most common while the dose is being raised, and a new medicine usually means a new step-up.^1,12

In SURMOUNT-1, stomach effects on Zepbound occurred “primarily during dose escalation.”¹² On Zepbound 5, 10 or 15 mg, 25 to 29 in 100 people had nausea. On a dummy injection (placebo), 8 in 100 did.¹

Both labels carry a warning about severe stomach side effects. Losing fluid through vomiting or diarrhea can also harm the kidneys.^1,2

Does switching to Zepbound add more weight loss?

No trial we found has tested a switch. The one head-to-head trial, SURMOUNT-5, gave people one medicine or the other from the start.⁸

Because no one in SURMOUNT-5 switched, it can’t tell you what happens after a move from Wegovy to Zepbound. Our Zepbound vs Wegovy page covers the trial in full.

What about switching from a compounded version?

A prescriber works from the approved label, not from the compounded dose. The FDA says compounded drugs are not FDA-approved, and it has reports of hospital stays linked to dosing errors with compounded semaglutide.¹³

• Different ingredients: the FDA says the salt forms some compounders used, semaglutide sodium and semaglutide acetate, “are different active ingredients” from those in the approved drugs.¹³
• Dosing errors: the FDA lists people measuring incorrect doses, clinicians miscalculating doses, and doses beyond the approved label.¹³

So the number on a compounded vial may not match a brand’s dose. Bring the vial or its label to your prescriber. Our compounded GLP‑1 post covers the rules.

What paperwork does a switch need in the US?

A new prescription, and often a new insurance approval. Medicare’s GLP‑1 Bridge says plainly that switching from one covered drug to another needs a new prior authorization.¹⁰

• Medicare GLP‑1 Bridge: covers Foundayo, Wegovy (injection and tablets) and the Zepbound KwikPen for weight. “If you switch a patient from one GLP‑1 drug to another, you’ll have to complete a new prior authorization.”¹⁰
• Employer and marketplace plans: each plan sets its own rules, and some prefer one brand over another. Our prior authorization post and CVS Caremark page show how this works.

Ask your prescriber’s office to start the new approval before your old supply runs out. That way a paperwork gap doesn’t turn into missed doses.

Questions people ask

How we researched this

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