Which one causes more weight loss?

Each label reports results from its own trials, and those are not head to head figures. A clinician comparing them for a specific person is doing something a reference page cannot do.

Are the side effects the same?

The common ones are largely digestive for both, and both carry a boxed warning about thyroid tumours seen in animals. The details are in the table and on each medicine's page.

Can you switch between them?

Switching is a prescribing decision, and neither label sets out how to do it. Anyone considering it should ask the person who prescribes.

Comparison

Mounjaro and Ozempic, compared from both labels

Two different substances, both injected weekly, both approved in the United States for type 2 diabetes under these brand names. The comparison people usually want is about weight, and that is where the labels stop being able to answer.

From the approved label

The two labels, side by side

	Mounjaro	Ozempic
Approved uses	MounjaroMOUNJARO ® is a glucose-dependent insulinotropic polypeptide (GIP) receptor and glucagon-like peptide-1 (GLP-1) receptor agonist indicated as an adjunct to diet and exercise to improve glycemic control in adults and pediatric patients 10 years of age and older with type 2 diabetes mellitus.	Ozempicas an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus.
Forms and strengths	MounjaroInjection: Clear, colorless to slightly yellow solution in pre-filled single-dose pens, single-dose vials, multi-dose vials, or single-patient-use KwikPens, each available in the following strengths.; The multi-dose vials and single-patient-use KwikPen each contain 4 doses: Single-dose Pen or Vial 2.5 mg/0.5 mL 5 mg/0.5 mL 7.5 mg/0.5 mL 10 mg/0.5 mL 12.5 mg/0.5 mL 15 mg/0.5 mL Multi-dose Vial (4...	OzempicInjection: 2 mg/3 mL (0.68 mg/mL) for 4 doses of 0.25 mg and 2 doses of 0.5 mg or 4 doses of 0.5 mg, 4 mg/3 mL (1.34 mg/mL) for 4 doses of 1 mg, and 8 mg/3 mL (2.68 mg/mL) for 4 doses of 2 mg in...; Injection: 0.25 mg, 0.5 mg or 1 mg per 0.5 mL in a single-dose prefilled syringe
How it is taken	MounjaroThe recommended starting dosage is 2.5 mg injected subcutaneously once weekly.	OzempicAdminister once weekly at any time of day, with or without meals.
Must not be used when	MounjaroMOUNJARO is contraindicated in patients with: A personal or family history of medullary thyroid carcinoma (MTC) or in patients with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).; Known serious hypersensitivity to tirzepatide or any of the excipients in MOUNJARO.; Serious hypersensitivity reactions, including anaphylaxis and angioedema, have been reported with MOUNJARO.	OzempicPersonal or family history of MTC or in patients with MEN 2.; Serious hypersensitivity reaction to semaglutide or any of the excipients in OZEMPIC.
Common side effects	Mounjaromost common adverse reactions, reported in ≥5% of patients treated with MOUNJARO are nausea, diarrhea, decreased appetite, vomiting, constipation, dyspepsia, and abdominal pain.	Ozempicmost common adverse reactions reported in ≥5% of patients treated with OZEMPIC are: nausea, vomiting, diarrhea, abdominal pain and constipation.
Boxed warning	MounjaroWARNING: RISK OF THYROID C-CELL TUMORS	OzempicWARNING: RISK OF THYROID C-CELL TUMORS
Label holder	MounjaroEli Lilly and Company	OzempicA-S Medication Solutions
Label version	Mounjaro22 April 2026	Ozempic30 July 2026

Built at page render time from the same imported label data as the medicine pages, so it cannot drift away from them.

Written by us

Different molecules, similar mechanism

Semaglutide acts on one gut hormone receptor. Tirzepatide acts on that one and a second. Both slow stomach emptying and reduce appetite, and both lower blood sugar, which is why both hold diabetes approvals.

In Europe the picture differs from the American one: the European authorisation for Mounjaro covers weight management as well as diabetes, so the same brand name carries both indications. Reading American sources about Mounjaro without knowing that is a common source of confusion.

Why this page gives no verdict

Neither label makes a claim about the other, and trial results quoted out of context are not a comparison: different trials enrol different people under different conditions.

What can be compared is what the documents state, and that is what the table above does: indications, forms, dosing, contraindications and warnings, taken from each label without interpretation.

Questions

Which one causes more weight loss?: Each label reports results from its own trials, and those are not head to head figures. A clinician comparing them for a specific person is doing something a reference page cannot do.
Are the side effects the same?: The common ones are largely digestive for both, and both carry a boxed warning about thyroid tumours seen in animals. The details are in the table and on each medicine's page.
Can you switch between them?: Switching is a prescribing decision, and neither label sets out how to do it. Anyone considering it should ask the person who prescribes.

Sources

Mounjaro, Mounjaro KwikPen: prescribing informationDailyMed, US National Library of Medicine. Label version 22 April 2026
Ozempic: prescribing informationDailyMed, US National Library of Medicine. Label version 30 July 2026