Staging preview: health content pending qualified review
D2C Peptides

Side effects

Tirzepatide side effects

In trials of the approved injectable, tirzepatide's most common side effects were nausea, diarrhea, vomiting and constipation, mostly while the dose was being raised.12 In the weight-reduction trials, 56% had stomach or bowel effects versus 30% on placebo.3 The labels also warn of rarer serious risks, including pancreatitis, gallbladder disease and thyroid C-cell tumors seen in rats.456

This page summarizes published sources for information only. It is not medical advice and does not tell anyone to use a product. Questions about your own health belong with a licensed clinician. For questions about an order or a product, contact us.

Most common side effects

The Mounjaro label reports rates from placebo-controlled trials in adults with type 2 diabetes, and the Zepbound label from weight-reduction trials in adults with obesity or overweight.78 Each range below spans the 5, 10 and 15 mg doses.

Side effect Type 2 diabetes trials Weight-reduction trials
Nausea 12% to 18% vs 4% on placebo7 25% to 29% vs 8%8
Diarrhea 12% to 17% vs 9%7 19% to 23% vs 8%8
Vomiting 5% to 9% vs 2%7 8% to 13% vs 2%8
Constipation 6% to 7% vs 1%7 11% to 17% vs 5%8
Indigestion 5% to 8% vs 3%7 9% to 10% vs 4%9
Abdominal pain 5% to 6% vs 4%7 9% to 10% vs 5%8
Decreased appetite 5% to 11% vs 1%7 not listed in this table

Most nausea, vomiting and diarrhea occurred during dose increases and decreased over time.1 Overall, stomach and bowel effects affected 37% to 44% of people in the diabetes trials versus 20% on placebo.10 In the weight-reduction trials the figure was 56% versus 30%.3 In those trials, 4.8% to 6.7% stopped treatment because of side effects, versus 3.4% on placebo.11

Other side effects in the label tables

Rates are from the weight-reduction trials unless noted.

  • Injection site reactions: 6% to 8% versus 2% on placebo, and 3.2% versus 0.4% in the diabetes trials.912
  • Fatigue: 5% to 7% versus 3%.9
  • Allergic reactions: 5% versus 3%, mostly skin reactions such as rash or itching.913
  • Hair loss: 4% to 5% versus 1%, reported in 7.1% of women and 0.5% of men on tirzepatide.914
  • Burping, reflux, gas and bloating: burping 4% to 5% versus 1%, reflux 4% to 5% versus 2%, gas and bloating 3% to 4% versus 2%.915
  • Dizziness: 4% to 5% versus 2%.15
  • Low blood pressure: 1.6% versus 0.1%.16
  • Faster heart rate: an average rise of 1 to 3 beats per minute, and 2 to 4 in the diabetes trials.1718
  • Low blood sugar: 4.2% versus 1.3% in a weight-reduction trial of people with type 2 diabetes.19

Serious risks and warnings

  • Thyroid C-cell tumors (boxed warning): tirzepatide caused these tumors in rats.6 Whether it causes them in humans, including medullary thyroid carcinoma, is unknown.6 The labels rule out use with a personal or family history of medullary thyroid carcinoma or MEN 2.20
  • Pancreatitis: acute pancreatitis, including fatal cases, has been seen with GLP-1 receptor agonists or tirzepatide.4 In the diabetes trials it occurred in 0.23 versus 0.11 patients per 100 years of exposure on comparators.21 The label says to stop treatment if pancreatitis is suspected.22
  • Gallbladder disease: 0.6% versus 0% in the diabetes trials.5 In the weight-reduction trials, gallstones affected 1.1% versus 1%, and gallbladder inflammation 0.7% versus 0.2%.23
  • Kidney injury: 0.5% versus 0.2% in the weight-reduction trials.24 Most reported cases occurred in people dehydrated by nausea, vomiting or diarrhea, and some cases reported after approval needed dialysis.2526
  • Severe stomach and bowel reactions: 1.7% to 3.1% versus 1% in the weight-reduction trials.27 Tirzepatide is not recommended in severe gastroparesis.28
  • Serious allergic reactions: anaphylaxis and angioedema have been reported.29
  • Low blood sugar with other diabetes medicines: the risk, including severe low blood sugar, may rise with insulin or a sulfonylurea.30
  • Diabetic eye disease: rapid improvement in blood sugar has been linked to temporary worsening of diabetic retinopathy.31
  • Anesthesia: rare cases of stomach contents entering the lungs during general anesthesia or deep sedation have been reported with GLP-1 receptor agonists.32
  • Liver: LiverTox reports few cases of raised liver enzymes during therapy and rare cases of clinically apparent liver injury.33
  • Reported after approval: ileus, intestinal obstruction and severe constipation with fecal impaction.34

Medicines, pregnancy and other groups

  • Birth control pills: tirzepatide can make them less effective. The labels advise a non-oral method, or an added barrier method, for 4 weeks after starting and after each dose increase.35
  • Oral medicines: it slows stomach emptying, so the label advises monitoring medicines with a narrow therapeutic range, such as warfarin.3637
  • Other GLP-1 medicines: the Zepbound label advises against combining it with other tirzepatide products or any GLP-1 receptor agonist.38
  • Pregnancy: animal studies suggest possible harm to a fetus, and the Zepbound label says to stop it once a pregnancy is recognized.3940
  • Breastfeeding: after one 5 mg dose in 11 breastfeeding women, tirzepatide was undetectable in 164 of 171 milk samples.41
  • Children: Zepbound's safety is not established in children, and Mounjaro's is not established under age 10.4243

Antibodies and label changes

Antibodies to tirzepatide formed in 51% of people in the diabetes trials and 64.5% in the main weight-reduction trials.4445 No clinically significant effect on drug levels or effectiveness was found, but people with antibodies had more allergic and injection site reactions.46 In February 2026, the Zepbound label removed its warning on suicidal behavior and ideation.47

Compounded and research-labeled products

These rates come from trials of the approved product. By May 31, 2026, FDA had received more than 730 adverse event reports linked to compounded tirzepatide.48 It has also received reports that may be related to compounded semaglutide or tirzepatide prescribed above the label dose.49 FDA warns that research-labeled GLP-1 products sold to consumers are of unknown quality and may be harmful.50 General precautions are in Peptide safety basics.

Back to the Tirzepatide profile. Related: Tirzepatide dosage, Tirzepatide benefits and uses and How to reconstitute Tirzepatide.

More on Tirzepatide

  • Tirzepatide dosage

    Published dosing information for Tirzepatide from labels and studies, with its source, and why it is not advice for you.

  • Tirzepatide benefits and uses

    What published sources report about Tirzepatide and its uses, with the evidence level of each finding. No promises.

  • How to reconstitute Tirzepatide

    How Tirzepatide is reconstituted, the supplies used, and the calculator, step by step. Sourced and reviewed.

Frequently asked questions

What are the possible side effects of taking tirzepatide?

The most common are stomach and bowel effects: nausea, diarrhea, vomiting, constipation, indigestion and abdominal pain.78 Nausea affected 25% to 29% of people in the weight-reduction trials, versus 8% on placebo.8 Less common effects include injection site reactions, fatigue, hair loss and dizziness.915 Rarer serious risks include pancreatitis, gallbladder disease and kidney injury after dehydration.4526

Is tirzepatide hard on your body?

Most of the burden falls on the gut. In the weight-reduction trials, 56% had stomach or bowel side effects versus 30% on placebo, and 4.8% to 6.7% stopped treatment because of side effects, versus 3.4% on placebo.311 Severe stomach and bowel reactions affected 1.7% to 3.1%, versus 1%.27 The labels also carry a boxed warning about thyroid C-cell tumors seen in rats.6

Who should not take tirzepatide?

The labels rule out use with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2, and with a known serious allergy to tirzepatide or the product's ingredients.20 It is not recommended in severe gastroparesis.28 Zepbound is stopped once a pregnancy is recognized, and safety is not established in children for Zepbound or under age 10 for Mounjaro.404243

What not to do on tirzepatide?

The Zepbound label advises against combining it with other tirzepatide products or any GLP-1 receptor agonist.38 The labels ask patients to tell healthcare providers about any planned surgery or procedure, because of rare cases of aspiration under anesthesia.5132 People on birth control pills are advised to switch to a non-oral method, or add a barrier method, for 4 weeks after starting and after each dose increase.35 A KwikPen must never be shared, even with a new needle.52

Written by D2C Peptides Editorial Team.

Pending qualified review.

Updated .

Sources

  1. MOUNJARO Prescribing Information, revised 08/2026: Gastrointestinal adverse reactions (timing). U.S. Food and Drug Administration (label for Eli Lilly and Company), 2026.
  2. SURMOUNT-1 abstract: cardiometabolic measures and adverse events (PMID 35658024). New England Journal of Medicine (via NLM PubMed E-utilities), 2022.
  3. ZEPBOUND Prescribing Information, revised 08/2026: Gastrointestinal adverse reactions. U.S. Food and Drug Administration (label for Eli Lilly and Company), 2026.
  4. Same source as 1: Acute pancreatitis.
  5. Same source as 1: Acute gallbladder disease.
  6. Same source as 1: Boxed warning.
  7. Same source as 1: Table 1 (placebo, 5 mg, 10 mg, 15 mg; % of adults with type 2 diabetes).
  8. Same source as 3: Table 1, weight-reduction trials (placebo, 5 mg, 10 mg, 15 mg; %).
  9. Same source as 3: Table 1 continued (placebo, 5 mg, 10 mg, 15 mg; %).
  10. Same source as 1: Gastrointestinal adverse reactions (incidence).
  11. Same source as 3: Discontinuations.
  12. Same source as 1: Injection site reactions.
  13. Same source as 3: Hypersensitivity reactions.
  14. Same source as 3: Hair loss.
  15. Same source as 3: Table 1 continued (placebo, 5 mg, 10 mg, 15 mg; %).
  16. Same source as 3: Hypotension.
  17. Same source as 3: Heart rate.
  18. Same source as 1: Heart rate increase.
  19. Same source as 3: Hypoglycemia.
  20. Same source as 1: Contraindications.
  21. Same source as 1: Pancreatitis incidence.
  22. Same source as 1: Highlights, acute pancreatitis.
  23. Same source as 3: Acute gallbladder disease.
  24. Same source as 3: Acute kidney injury.
  25. Same source as 1: Acute kidney injury (cause).
  26. Same source as 1: Acute kidney injury.
  27. Same source as 3: Severe gastrointestinal adverse reactions.
  28. Same source as 1: Gastroparesis.
  29. Same source as 1: Serious hypersensitivity.
  30. Same source as 1: Hypoglycemia.
  31. Same source as 1: Diabetic retinopathy.
  32. Same source as 1: Pulmonary aspiration.
  33. Tirzepatide, CID 156588324: LiverTox Summary annotation. PubChem, NIH National Library of Medicine (source: LiverTox, NIDDK), 2026.
  34. Same source as 1: Postmarketing experience.
  35. Same source as 1: Oral contraceptives.
  36. Same source as 1: Gastric emptying.
  37. Same source as 1: Oral medications.
  38. Same source as 3: Indications (OSA) and limitations of use.
  39. Same source as 1: Pregnancy.
  40. Same source as 3: Pregnancy.
  41. Same source as 1: Lactation.
  42. Same source as 3: Pediatric use.
  43. Same source as 1: Pediatric use under 10.
  44. Same source as 1: Immunogenicity (incidence).
  45. Same source as 3: Immunogenicity.
  46. Same source as 1: Immunogenicity (effects).
  47. Same source as 3: Recent Major Changes.
  48. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss (content current as of 10/01/2026): adverse event reports. U.S. Food and Drug Administration, 2026.
  49. Same source as 48: doses above the label.
  50. Same source as 48: consumer warning.
  51. Same source as 1: Procedures.
  52. Same source as 3: KwikPen sharing.