Tirzepatide side effects and risks

Reported side effects

• Nausea: 5/10/15 mg: 25/29/28%; placebo 8%., moderate. Review fluids and food intake; contact the prescriber if persistent or severe. (source)
• Diarrhea: 5/10/15 mg: 19/21/23%; placebo 8%., moderate. Review fluids and food intake; contact the prescriber if persistent or severe. (source)
• Constipation: 5/10/15 mg: 17/14/11%; placebo 5%., moderate. Review fluids and food intake; contact the prescriber if persistent or severe. (source)
• Vomiting: 5/10/15 mg: 8/11/13%; placebo 2%., moderate. Persistent vomiting or inability to drink needs prompt care. (source)
• Stomach pain: 5/10/15 mg: 9/9/10%; placebo 5%., mild (source)
• Indigestion: 5/10/15 mg: 9/9/10%; placebo 4%., mild (source)
• Injection-site reaction: 5/10/15 mg: 6/8/8%; placebo 2%., mild (source)
• Fatigue: 5/10/15 mg: 5/6/7%; placebo 3%., mild (source)
• Hair loss: 5/10/15 mg: 5/4/5%; placebo 1%., mild (source)
• Reflux: 5/10/15 mg: 4/4/5%; placebo 2%., mild (source)
• Burping: 5/10/15 mg: 4/5/5%; placebo 1%., mild (source)
• Gas or bloating: 5/10/15 mg: 3/3/4%; placebo 2%., mild (source)
• Dizziness: 5/10/15 mg: 4/5/4%; placebo 2%., mild (source)
• Low blood pressure: 5/10/15 mg: 1/1/2%; placebo 0%., moderate (source)

Stop and get help if

• Severe, persistent belly pain, especially reaching the back: Stop dosing and get urgent medical assessment for pancreatitis.
• Swollen tongue or throat, trouble breathing, collapse: Call emergency services now; do not take another dose.
• Upper-right belly pain with fever or yellow skin: Get urgent care for possible gallbladder or bile-duct disease.
• Ongoing vomiting, very little urine, inability to keep fluids down: Get urgent assessment for dehydration and kidney injury.
• Severe bloating with vomiting and no stool or gas: Get urgent care for possible bowel blockage.
• Confusion, seizure, fainting or low glucose that does not resolve: Get emergency help; severe low blood sugar needs prompt treatment.
• Sudden loss of vision or new major vision change: Get urgent eye assessment the same day.
• Chest pain, collapse or severe shortness of breath: Call emergency services now.
• New neck lump, trouble swallowing or persistent hoarseness: Arrange prompt medical assessment.

Who should avoid it

• pregnant: Stop weight-loss use when pregnancy is recognized; human safety data are inadequate and animal studies found fetal harm.
• tryingToConceive: UK guidance says stop at least 1 month before a planned pregnancy.
• breastfeeding: A single-dose study found low milk transfer, but infant effects and repeated dosing remain unknown.
• under18: Mounjaro is licensed from age 10 for type 2 diabetes; that does not authorize pediatric weight-loss use.
• mtcOrMen2: Formal US contraindication: personal or family medullary thyroid cancer, or MEN2.
• other: Do not use after a serious allergy to tirzepatide or an ingredient.
• eatingDisorderHistory: Screen for restrictive intake, bingeing and nutritional harm.
• pancreatitisHistory: Review prior pancreatitis. Stop for suspected pancreatitis; NICE says do not restart after confirmed pancreatitis.
• gallbladderDisease: Gallstones and gallbladder inflammation can occur, especially with weight reduction.
• gastroparesis: Not recommended with severe delayed stomach emptying; review persistent vomiting or severe constipation before dosing.
• kidneyDisease: No label dose adjustment, including dialysis. Vomiting or diarrhea can still cause dehydration and kidney injury.
• liverDisease: No label dose adjustment is required. Advanced illness and poor intake still need individualized review.
• diabeticRetinopathy: Rapid glucose improvement can briefly worsen eye disease. Monitor existing retinopathy and new vision symptoms.
• diabetes: Review glucose-lowering medicines and monitor sugar. Type 1 diabetes still requires insulin.
• heartCondition: Review fluid status, dizziness and blood pressure medicines; heart-failure evidence is specific to obesity with preserved ejection fraction.
• surgeryPlanned: Tell the anesthesia team; slowed stomach emptying can leave food in the stomach despite fasting. Plan dosing and fasting together.
• testedAthlete: Markers of tirzepatide are monitored in and out of competition in 2026. Monitoring is not prohibition.

Interactions

• Insulin: Low blood sugar risk rises. Insulin doses may need clinician-led adjustment; never simply stop insulin in type 1 diabetes.
• Sulfonylureas and other insulin secretagogues: Low blood sugar becomes more likely; the prescriber may reduce the secretagogue dose.
• Oral hormonal contraception: Use non-oral contraception or add a barrier for 4 weeks after starting and after each dose increase; stomach emptying changes absorption.
• Narrow-window oral medicines, including warfarin: Delayed stomach emptying can alter absorption. Review effect or drug levels; check INR when clinically indicated for warfarin.
• Other oral medicines: Review medicines that need a threshold concentration for effect. Absorption may change, especially after starting or increasing the dose.
• Another tirzepatide product or GLP-1 drug: Zepbound labeling advises against another tirzepatide product or GLP-1 drug. Overlapping effects can worsen vomiting and low intake.
• Amylin-type appetite drugs: Extra appetite suppression and vomiting are concerns. A controlled research combination does not validate a home-mixed stack.
• Diuretics and blood pressure medicines: This is a fluid and blood-pressure concern, not a proven direct drug interaction. Poor intake or diarrhea can worsen dizziness and dehydration.
• DPP-4 inhibitors: NICE guidance advises against combining DPP-4 inhibitors with tirzepatide because they act on the same pathway.

Product quality risks

• FDA reports fraudulent compounded-product labels, dosing errors and unapproved online products; counterfeit packaging can mislead.
• A 2026 analysis found a tirzepatide/B12 reaction impurity; clinical effects remain unknown.
• A purity percentage does not establish the correct dose, identity, sterility or endotoxin level.
• Poison-center data include serious outcomes, but class-wide reports do not give a tirzepatide user’s risk.