What the labels contain
- Zepbound®: says combining it with other tirzepatide products or any GLP-1 receptor agonist is not recommended. No section on switching to another medicine [1].
- Wegovy®: says using it with other semaglutide products or any other GLP-1 receptor agonist is not recommended. Its switching section (2.5) covers only Wegovy® injection and Wegovy® tablets [2].
- The Wegovy® starting dose and steps (section 2.2) are written for anyone starting Wegovy® [2].
Why there is no dose conversion
The two medicines have different active ingredients, and each label lists its own starting dose and steps for people starting it. No label turns a dose of one into a dose of the other, so a conversion table found elsewhere is not something the labels support. Where to start on the new medicine is set by your prescriber.
Side by side, from the labels
| Label item | Zepbound® | Wegovy® (injection) |
|---|---|---|
| Active ingredient | Tirzepatide, a GIP and GLP-1 receptor agonist | Semaglutide, a GLP-1 receptor agonist |
| Maker | Eli Lilly and Company | Novo Nordisk |
| FDA-approved uses | With diet and physical activity: long-term weight reduction in adults with obesity, or overweight plus a weight-related condition; moderate to severe obstructive sleep apnea in adults with obesity. Not established in children. [1] | With diet and physical activity: lowering the risk of major cardiovascular events in adults with cardiovascular disease and obesity or overweight; long-term weight reduction in adults and children 12 and older with obesity, and in adults with overweight plus a weight-related condition; MASH with moderate to advanced liver fibrosis in adults (accelerated approval). [2] |
| How it is taken | Once a week, under the skin of the abdomen or thigh, or the back of the upper arm, at any time of day. | Once a week, under the skin of the abdomen, thigh or upper arm. The same label also covers Wegovy® tablets, taken once a day. |
| Forms in the US | Single-dose pens, single-dose vials, multi-dose vials and the KwikPen® (four doses per pen) (section 3). | Single-dose pens (one strength sold as Wegovy® HD), single-dose syringes and the FlexTouch® multi-dose pen (section 3). |
| Dose steps | Sections 2.1–2.2 of the label: a starting dose that is not a maintenance dose, raised in steps of at least 4 weeks, then a maintenance dose that depends on the use. Not repeated here; your prescriber sets your steps. [1] | Section 2.2 of the label: a low starting dose raised every 4 weeks, then a maintenance dose that depends on the use. Not repeated here; your prescriber sets your steps. [2] |
| Half-life (section 12.3) | About 5 days (5 to 6 days in people with overweight or obesity) [1] | About 1 week [2] |
| Most common side effects (label) | Nausea, diarrhea, vomiting, constipation, abdominal pain, indigestion, injection-site reactions, fatigue, allergic reactions, burping, hair loss, reflux. | Nausea, diarrhea, vomiting, constipation, abdominal pain, headache, fatigue, indigestion, dizziness and others listed in the label. |
| Storage (label) | Refrigerated (2–8 °C). Single-dose pens and vials may be kept unrefrigerated up to 30 °C for a total of 21 days. Multi-dose vials and KwikPens® are discarded 30 days after first use or after 4 doses. | Refrigerated (2–8 °C). A single-dose pen may be kept at 8–30 °C for up to 28 days; a FlexTouch® pen for up to 56 days after first use. Not to be frozen. |
| Boxed warning | Yes: risk of thyroid C-cell tumors. | Yes: risk of thyroid C-cell tumors. |
| In the EU (EMA) | Not a separate EU product: in the EU, tirzepatide for weight management is authorised under the Mounjaro® name. [4] | Authorised since 2022 for weight management in adults and in adolescents 12 and older who weigh more than 60 kg; tablets for adults only. [3] |
Timing facts from the labels
| Label item | Zepbound® | Wegovy® (injection) |
|---|---|---|
| Half-life (section 12.3) | About 5 days (5 to 6 days in people with overweight or obesity) [1] | About 1 week [2] |
| Time to peak level (section 12.3) | About 24 hours (8 to 72) after a dose [1] | 1 to 3 days after an injection [2] |
| Steady state (section 12.3) | After 4 weeks of weekly doses [1] | The label gives steady-state levels, not a time to reach them [2] |
| After the last dose (section 12.3) | Not stated in the label [1] | About 5 to 7 weeks in the circulation after the last dose [2] |
| Missed dose (section 2) | Taken within 4 days (96 hours); after that, skipped (section 2.3) [1] | Given if the next dose is more than 2 days away, otherwise skipped (section 2.4) [2] |
| Section on switching | None [1] | Section 2.5, between Wegovy® injection and Wegovy® tablets only [2] |
Switching the other way
Moving from Wegovy® to Zepbound® is not covered by either label [2][1]. The Zepbound® starting dose (section 2.1) is written for anyone starting Zepbound®; where a person coming from semaglutide begins is your prescriber’s call.
Questions to bring to your prescriber
- When should the last Zepbound® dose be, and when the first Wegovy® dose?
- Where on the Wegovy® steps will I start, and when is the next step reviewed?
- Is any surgery or sedation planned? The Wegovy® label has a warning about it (section 5.10) [2].
- Which side effects should I report, and how quickly?
Ozempic®, Wegovy®, Rybelsus®, Saxenda®, Victoza® and FlexTouch® are registered trademarks of Novo Nordisk A/S. Mounjaro®, Zepbound® and KwikPen® are registered trademarks owned or licensed by Eli Lilly and Company; Foundayo™ is a trademark of Eli Lilly and Company. PepLabo is not affiliated with or endorsed by these companies.
