Mounjaro and Wegovy are prescription medicines whose names, approved uses, and formulations need careful checking. For weight management, the comparison also involves Zepbound, another brand containing the same active ingredient as Mounjaro.
This adult-focused overview uses U.S. prescribing information, UK regulatory guidance, and selected Korean MFDS product records, reviewed September 11, 2026. Country-specific information is identified below. Use the exact current local product information with your prescriber; approval does not guarantee local stock or individual eligibility.
Start with the ingredient, country, and formulation
Tirzepatide activates GIP and GLP-1 receptors; semaglutide activates GLP-1 receptors. These pathways are involved in appetite and glucose regulation. Different milligram strengths are not directly interchangeable between medicines. Mounjaro prescribing information; Wegovy prescribing information.
| Brand / ingredient | How to interpret it |
|---|---|
| Mounjaro Tirzepatide | The U.S. label covers type 2 diabetes and cardiovascular risk reduction in specified adults with type 2 diabetes. UK authorization also includes weight management for eligible adults. Check the country before describing its approved use. |
| Zepbound Tirzepatide | U.S. indications include long-term weight reduction and maintenance in eligible adults, and moderate-to-severe obstructive sleep apnea in adults with obesity. |
| Wegovy Semaglutide | U.S. weight-management labeling includes weekly injections and daily tablets, with different instructions. This article’s direct comparison evidence concerns the injection regimens used in SURMOUNT-5. |
Sources: Mounjaro U.S. label, Zepbound U.S. label, Wegovy U.S. label, and MHRA’s Mounjaro authorization. Weight-management treatment is used alongside dietary and physical-activity support.
Other familiar names: UK guidance distinguishes Ozempic, a semaglutide diabetes medicine, from Wegovy, and also lists Saxenda, containing liraglutide, for weight management. A shared drug family does not make these products equivalent. MHRA brand and indication guide.
What did the direct comparison actually show?
SURMOUNT-5 randomized 751 adults without diabetes who had obesity, or overweight with a qualifying weight-related condition. Over 72 weeks, it compared weekly tirzepatide at a maximum tolerated 10 or 15 mg with weekly semaglutide at 1.7 or 2.4 mg. Both groups received diet and physical-activity counseling. The trial was open-label and sponsored by Eli Lilly, the manufacturer of tirzepatide.
Average body-weight change at 72 weeks
Tirzepatide: −20.2%
Semaglutide: −13.7%
Read the 2025 published trial and sponsor’s detailed results. The trial does not establish a universal “best drug”; tolerability, other health conditions, and access also matter.
A 2026 formulation check: The current U.S. Wegovy label includes oral tablets and a 7.2 mg injection presentation. SURMOUNT-5 did not compare those regimens. Its results should not be presented as a head-to-head test against them. Current Wegovy label.
What happens when treatment stops?
Weight regain is an important planning issue. In the STEP 1 extension, participants regained about two-thirds of their previous weight loss during the year after semaglutide and the structured lifestyle intervention were withdrawn. This was a follow-up study in a subset of participants, not a prediction for every patient. STEP 1 extension.
In SURMOUNT-4, participants first received tirzepatide for 36 weeks. During the following 52 randomized weeks, those switched to placebo gained an average 14.0% relative to their week-36 weight, while those continuing tirzepatide lost a further 5.5%. These percentages use a different starting point from the initial-treatment comparison above. SURMOUNT-4 randomized withdrawal trial.
Discuss a maintenance plan, follow-up, and affordability before starting. These studies support planning beyond an initial weight-loss phase; they do not supply a do-it-yourself stopping or switching schedule.
For a closer look at the withdrawal studies and appointment questions, read Stopping Mounjaro or Wegovy: weight regain evidence and maintenance planning.
Side effects and circumstances to discuss first
See our dedicated side-effects guide for trial rates, urgent warning signs and updated regulatory safety information.
The following summary uses U.S. prescribing information. For treatment in Korea or another market, review that product’s local cautions as well.
Common effects include nausea, vomiting, diarrhea, and constipation. Important risks include pancreatitis, gallbladder problems, dehydration-related kidney injury, and low blood sugar when combined with insulin or certain diabetes medicines. Severe gastroparesis requires particular attention. Zepbound safety information; Wegovy safety information.
The U.S. labels contraindicate use with a personal or family history of medullary thyroid carcinoma or MEN2, and with relevant serious hypersensitivity. The thyroid warning is based on rodent findings; the human relevance remains unknown. Mounjaro boxed warning and contraindications; Wegovy boxed warning and contraindications.
- Pregnancy planning: Weight-loss treatment is not for pregnancy. For weight management, Wegovy’s label calls for stopping at least two months before a planned pregnancy; discuss the appropriate plan with your prescriber. Wegovy pregnancy guidance.
- Oral contraception with tirzepatide: The label advises a non-oral method or an added barrier method for four weeks after starting and four weeks after each dose increase. Mounjaro contraceptive guidance.
- Procedures and other medicines: Tell the care team about planned anesthesia or sedation and every medicine you take. Do not combine these treatments or switch between them without clinical guidance. Zepbound precautions and limitations.
Severe persistent abdominal pain, especially with vomiting, needs urgent medical assessment. Trouble breathing or swelling of the face or throat requires emergency help. These are not symptoms to manage by changing the dose yourself. Zepbound Medication Guide.
Using the comparison in South Korea
The Korean MFDS records linked by the local manufacturers identify both products as prescription medicines. The Mounjaro record includes adult type 2 diabetes and chronic weight management; the Wegovy record includes weight loss and maintenance. The U.S. distinction between Mounjaro and Zepbound should therefore not be copied into a description of Korean Mounjaro.
Adult weight-management criteria in the records reviewed: an initial BMI of at least 30 kg/m², or at least 27 but below 30 kg/m² with one or more qualifying weight-related conditions. Treatment accompanies dietary and activity support. Meeting a BMI threshold alone does not establish individual suitability.
Sources: MFDS Mounjaro product record and MFDS Wegovy product record, accessed through the manufacturers’ Korean product pages on September 11, 2026. These linked records are not a complete inventory of every Korean indication or presentation.
Check the actual Korean pen and package
Lilly Korea’s FAQ describes its listed Mounjaro prefilled pen as single-use, with four pens per carton. The reviewed Wegovy prefilled-pen record describes a pen for four weekly administrations at its labeled strength. Do not assume that “one pen” means the same number of doses across brands or countries. Use the supplied instructions and your clinician’s demonstration. Lilly Korea FAQ; Novo Nordisk Korea product links.
Prescription and cost questions
Arrange a local medical consultation and obtain the prescribed product through a pharmacy, with pharmacist guidance. Ask for the medicine cost, consultation charges, follow-up costs, and the exact quantity supplied. Lilly Korea describes Mounjaro as non-reimbursed in its FAQ and says prices vary between institutions; a single quoted price should not be treated as a nationwide price. Official Korean price explanation.
For current labeling, return to Lilly Korea’s Mounjaro page or Novo Nordisk Korea’s obesity-medicine page. U.S. oral or high-dose Wegovy information does not establish Korean approval or availability. Avoid treating a social-media seller as a substitute for the prescription-and-pharmacy process.
How to obtain legitimate treatment
Start with a licensed clinician who can assess eligibility, medical history, and local approved options. Fill the prescription through a licensed pharmacy. In the U.S., FDA recommends a state-licensed pharmacy; UK readers can check the pharmacy registration routes linked in MHRA guidance. FDA access advice; MHRA pharmacy checks.
Ask for the full ongoing cost, including consultations and follow-up, and confirm coverage directly. A price from another country or an introductory offer does not establish your long-term cost or eligibility. This site explains these medicines and does not supply them or arrange prescriptions.
Be cautious with “equivalent” online products: FDA states that compounded products are not FDA-approved and has reported dosing errors, fraudulent labeling, and other concerns. An unapproved preparation is not automatically interchangeable with the licensed product. Offers without a clinical assessment or prescription deserve particular scrutiny. FDA’s current warning.
Five questions for your appointment
- Which locally approved treatment fits my health conditions and goals?
- Which formulation and monitoring plan are you recommending?
- What side effects require a call, urgent care, or stopping under medical guidance?
- How will we support nutrition, activity, and long-term weight maintenance?
- What happens if cost, supply, pregnancy plans, or side effects interrupt treatment?
For general nutrition label reading, see our protein foods and powders guide. It is background information, not a substitute for an individualized nutrition plan during treatment.
Educational comparison, not personal prescribing advice. This is a selective overview; consult the full current local prescribing information.