Canada · Side effects
Mounjaro and Zepbound side effects: what Canadians report.
Short answer
Mounjaro and Zepbound are both tirzepatide. The most common side effects are gastrointestinal — nausea, diarrhoea, vomiting, constipation — usually worst early on. The Health Canada labels also warn about pancreatitis, gallbladder problems and dehydration. Below: what the labels list, how to report a reaction in Canada, and what anonymous users in our archive describe. No dosing.
What the labels list
- Common: nausea, diarrhoea, vomiting, constipation, indigestion, abdominal pain, reduced appetite, injection-site reactions.
- Serious but less common: pancreatitis, gallbladder problems, dehydration-related kidney injury, low blood sugar with insulin or sulfonylureas, worsening diabetic eye disease.
- Thyroid warning: C-cell tumours in rodents; not for people with a history of medullary thyroid cancer or MEN 2.
- Oral contraceptives: absorption may be reduced after starting or increasing a dose.
Full product monographs are in Health Canada's Drug Product Database.
What tirzepatide users report
- 93 published anonymous tirzepatide confessions; 27 mention at least one side effect.
- 10 mention Mounjaro or Zepbound by name.
- Among confessions that state a weight change in pounds, the median reported is 50 lb. Self-reported, unverified.
Most-mentioned side effects (share of tirzepatide confessions):
- Heart rate or palpitations: 11.8% (11)
- Anxiety or panic: 5.4% (5)
- Burping: 4.3% (4)
- Insomnia or poor sleep: 3.2% (3)
- Libido: 3.2% (3)
Counts are phrase mentions in anonymous accounts, not diagnoses or clinical rates. Full breakdown and methodology: tirzepatide side-effects report.
Reporting a side effect in Canada
Tell your prescriber or pharmacist first. You can also report to the Canada Vigilance Program.
How common side effects were in trials
From SURMOUNT-1 (72 weeks, tirzepatide vs placebo).
| Side effect | Tirzepatide | Placebo |
|---|---|---|
| Nausea | 25% to 33% | 10% |
| Diarrhea | 19% to 23% | 7% |
| Constipation | 12% to 17% | 6% |
| Vomiting | 8% to 12% | 2% |
Most GI effects were mild to moderate and most common while the dose was being increased.
Last reviewed October 15, 2026against Health Canada's Drug Product Database and SURMOUNT-1.
Related
Frequently asked questions
- How common is nausea on Mounjaro?
- In SURMOUNT-1, 25% to 33% had nausea on tirzepatide vs 10% on placebo.
- What are the most common Mounjaro side effects?
- Gastrointestinal effects: nausea, diarrhoea, vomiting, constipation, indigestion and abdominal pain, mostly early on and when the dose is increased. Reduced appetite and injection-site reactions are also listed.
- What serious Mounjaro side effects should Canadians watch for?
- The labels warn about pancreatitis, gallbladder disease, low blood sugar with insulin or sulfonylureas, kidney problems from dehydration, diabetic eye changes and thyroid C-cell tumours in rodents. Severe ongoing abdominal pain needs urgent care.
- Does Mounjaro affect birth control pills?
- Tirzepatide can reduce how well oral contraceptives are absorbed, especially after starting or increasing a dose. Ask your prescriber or pharmacist about backup contraception.
- Are Zepbound side effects the same as Mounjaro?
- Yes. Both are tirzepatide from Eli Lilly; Mounjaro is authorized for type 2 diabetes and Zepbound for weight management.
- Is there a generic Mounjaro in Canada?
- No. As of October 2026, Health Canada's Drug Product Database lists tirzepatide only under Eli Lilly's Mounjaro and Zepbound.
- How do I report a side effect in Canada?
- Tell your prescriber or pharmacist, and you can report it to the Canada Vigilance Program (MedEffect Canada).
Sources
General information only — not medical, legal or regulatory advice. Peptide Confessions does not sell, source or recommend any product or vendor, and nothing here is dosing guidance. Speak with a licensed Canadian healthcare professional or pharmacist about any medication. Editorial process →