What is the same
Both are weekly injections under the skin, both are labelled for long-term weight reduction in adults with obesity or overweight plus a weight-related condition, and both carry a boxed warning about thyroid C-cell tumors [1][2].
What differs
- Active ingredient: semaglutide versus tirzepatide.
- Other approved uses: Wegovy® also covers cardiovascular risk reduction, MASH and children 12 and older; Zepbound® also covers moderate to severe obstructive sleep apnea in adults with obesity [1][2].
- Forms: Wegovy® in single-dose pens and syringes and a FlexTouch® pen, with Wegovy® tablets on the same label; Zepbound® in single-dose pens and vials, multi-dose vials and a KwikPen®.
- In the EU, tirzepatide for weight management is authorised as Mounjaro®, not Zepbound® [4].
Side by side, from the labels
| Label item | Wegovy® (injection) | Zepbound® |
|---|---|---|
| Active ingredient | Semaglutide, a GLP-1 receptor agonist | Tirzepatide, a GIP and GLP-1 receptor agonist |
| Maker | Novo Nordisk | Eli Lilly and Company |
| FDA-approved uses | 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). [1] | 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. [2] |
| How it is taken | Once a week, under the skin of the abdomen, thigh or upper arm. The same label also covers Wegovy® tablets, taken once a day. | Once a week, under the skin of the abdomen or thigh, or the back of the upper arm, at any time of day. |
| Forms in the US | Single-dose pens (one strength sold as Wegovy® HD), single-dose syringes and the FlexTouch® multi-dose pen (section 3). | Single-dose pens, single-dose vials, multi-dose vials and the KwikPen® (four doses per pen) (section 3). |
| Dose steps | 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. [1] | 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. [2] |
| Half-life (section 12.3) | About 1 week [1] | About 5 days (5 to 6 days in people with overweight or obesity) [2] |
| Most common side effects (label) | Nausea, diarrhea, vomiting, constipation, abdominal pain, headache, fatigue, indigestion, dizziness and others listed in the label. | Nausea, diarrhea, vomiting, constipation, abdominal pain, indigestion, injection-site reactions, fatigue, allergic reactions, burping, hair loss, reflux. |
| Storage (label) | 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. | 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. |
| Boxed warning | Yes: risk of thyroid C-cell tumors. | Yes: risk of thyroid C-cell tumors. |
| In the EU (EMA) | 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] | Not a separate EU product: in the EU, tirzepatide for weight management is authorised under the Mounjaro® name. [4] |
Timing facts from the labels
| Label item | Wegovy® (injection) | Zepbound® |
|---|---|---|
| Half-life (section 12.3) | About 1 week [1] | About 5 days (5 to 6 days in people with overweight or obesity) [2] |
| Time to peak level (section 12.3) | 1 to 3 days after an injection [1] | About 24 hours (8 to 72) after a dose [2] |
| Steady state (section 12.3) | The label gives steady-state levels, not a time to reach them [1] | After 4 weeks of weekly doses [2] |
| After the last dose (section 12.3) | About 5 to 7 weeks in the circulation after the last dose [1] | Not stated in the label [2] |
| Missed dose (section 2) | Given if the next dose is more than 2 days away, otherwise skipped (section 2.4) [1] | Taken within 4 days (96 hours); after that, skipped (section 2.3) [2] |
| Section on switching | Section 2.5, between Wegovy® injection and Wegovy® tablets only [1] | None [2] |
Using them together
The Wegovy® label says use with any other GLP-1 receptor agonist is not recommended [1]. The Zepbound® label says the same about other tirzepatide-containing products and any GLP-1 receptor agonist [2].
Moving between them, in either direction
Neither the Wegovy® (injection) label nor the Zepbound® label sets out a schedule for moving from one to the other [1][2]. The timing facts above describe each medicine on its own; they are not a plan for a change. If a switch comes up, in whichever direction, the gap, the first dose of the new medicine and its steps are set by your prescriber.
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.
