Tirzepatide Side Effects: What You Need to Know
Key takeaways:
Common tirzepatide side effects include nausea, constipation, diarrhoea, and stomach pain.
Serious side effects like pancreatitis or gallbladder issues are rare but require urgent medical attention.
Long-term tirzepatide side effects are still being studied, but research shows the medicine is generally safe for ongoing use.
Report side effects through the MHRA Yellow Card scheme, and follow your GP’s advice.
Tirzepatide is a Black Triangle medicine, requiring enhanced safety monitoring in the U.K.
If you’re prescribed tirzepatide, you might wonder what side effects to expect. Tirzepatide, sold in the United Kingdom under the brand name Mounjaro®, is used to treat obesity and type 2 diabetes.
Like all medicines, tirzepatide comes with potential side effects. Most are mild and temporary, while others are more serious and call for medical attention.
Below, we’ll discuss tirzepatide side effects and possible risks, as well as potential drug interactions.
How Tirzepatide Works
Tirzepatide is a dual GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide) receptor agonist. It’s injected into the fatty tissue under the skin (subcutaneously) once a week.
Tirzepatide works by mimicking two natural gut hormones — GLP-1 and GIP. These hormones help:
Regulate blood sugar levels
Increase insulin production after meals
Slow digestion, leading to feeling fuller for longer (satiety)
Reduce appetite and food intake
Since tirzepatide lowers blood sugar and helps you eat less, it can support weight loss in people with type 2 diabetes or obesity. It’s particularly effective when paired with lifestyle changes, such as healthy eating and regular physical activity.
In the U.K., the Medicines and Healthcare products Regulatory Agency (MHRA) authorised Mounjaro® for type 2 diabetes management and weight management in adults.
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Common Side Effects of Tirzepatide
The most common side effects of tirzepatide are gastrointestinal. These side effects often occur when starting treatment or increasing your dose. Usually, your side effects will improve within days or weeks as your body adjusts.
Common side effects of tirzepatide include:
Nausea
Constipation
Diarrhoea
Vomiting
Abdominal pain
Bloating or indigestion
Heartburn or acid reflux
Loss of appetite
Fatigue or lightheadedness
Injection site reactions (redness, swelling, or itching)
These side effects affect roughly one in 10 tirzepatide users. The effects are dose-dependent and more likely when starting treatment or increasing doses.
Tips to manage these symptoms include eating smaller meals, avoiding fatty or spicy foods, and drinking plenty of water. Non-prescription medicines may also help, but check with your GP or specialist before adding any new medication or supplements.
Serious Side Effects of Tirzepatide
Although uncommon, tirzepatide can cause serious side effects. These may include:
Inflammation of the pancreas (pancreatitis)
Rapid heartbeat (tachycardia)
Dehydration, particularly with vomiting or diarrhoea
Gallbladder problems, including gallstones or inflammation of the gallbladder (cholecystitis)
Low blood sugar (hypoglycaemia), especially when combined with insulin or sulfonylureas
Severe allergic reactions
Worsening diabetic retinopathy, an eye disease that affects people with diabetes
Kidney disease or kidney injury
Thyroid cancer risk, although thyroid tumours have only been shown in animal studies, not in humans
If you think you’re experiencing any of these side effects, stop tirzepatide immediately and seek urgent medical attention.
Tirzepatide is a Black Triangle medicine in the U.K. requiring enhanced safety monitoring. Report any side effects you experience through the MHRA Yellow Card scheme.
Tirzepatide Long-Term Side Effects
Research on tirzepatide long-term side effects is ongoing. Clinical trials so far suggest tirzepatide is generally safe and effective when used as prescribed. But data beyond a few years is limited.
Potential long-term health considerations:
Nutritional deficiencies. If your appetite loss is severe, and you don’t eat a healthy and balanced diet, you could develop nutritional deficiencies.
Muscle loss. When losing weight, you may also lose muscle mass. Strength training and adequate protein intake can help you maintain muscle.
Weight regain if treatment is stopped. If you stop using tirzepatide, you might regain some of the weight you lost, especially if you don’t stick to a reduced-calorie diet and maintain other healthy habits.
Thyroid tumours, kidney injury, or pancreatitis. While rare, these potential side effects are serious. If you’re at risk, your healthcare professional might suggest ongoing monitoring or using a different medication.
Tirzepatide is a relatively new medication. So, medical experts continue to collect safety data in real-world settings and through trials. Report any symptoms and side effects you experience through the MHRA Yellow Card scheme.
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Who Should Avoid Tirzepatide?
Tirzepatide isn’t suitable for everyone. Don’t use tirzepatide if you:
Have a personal or family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia syndrome type 2 (MEN 2)
Have had pancreatitis or severe gallbladder disease
Have uncontrolled gastrointestinal disease
Have severe kidney disease (renal impairment)
Have diabetes type 1
Are pregnant, planning pregnancy, or breastfeeding — it’s not yet clear whether tirzepatide is safe during pregnancy and lactation
Are over 75 years of age
Take other glucose-lowering medications
Always tell your GP about your health conditions and medications before starting tirzepatide. If tirzepatide isn’t suitable for you, your healthcare professional or a private clinician may be able to suggest a different approach to weight loss.
Tirzepatide Drug Interactions
Tirzepatide shouldn’t be combined with certain drugs. In some cases, it can reduce the absorption of medications. In other cases, combining tirzepatide can increase the risk or severity of side effects.
Potential tirzepatide drug interactions:
Oral contraceptives. Tirzepatide may reduce the absorption of birth control pills. Use condoms (barrier protection) as additional contraception during the first four weeks of treatment and four weeks after each dose increase.
Other diabetes medications. When combined with insulin and sulfonylureas, tirzepatide can cause numerous complications, including low blood sugar.
Other GLP-1 medications. Don’t combine tirzepatide with other GLP-1 receptor agonists, like liraglutide and semaglutide.
Before using tirzepatide, tell your healthcare professional about all the medications you take, including non-prescription medicines or supplements.
Tirzepatide Safety Tips
To make treatment safer and side effects easier to manage, keep these tips in mind:
Don’t combine tirzepatide with other medicines unless advised by a healthcare professional.
Try over-the-counter treatments and home remedies to manage mild side effects like nausea or heartburn — but check with your GP or pharmacist first.
Stay hydrated by drinking plenty of water. Consider an electrolyte mix if you’re experiencing diarrhoea, vomiting, or nausea.
Eat a balanced diet with a variety of nutrients and enough protein to prevent nutritional deficiencies or muscle loss.
Avoid high-fat foods or alcohol, as they can worsen indigestion and nausea.
Store tirzepatide pens or vials correctly — keep them refrigerated, or at room temperature if allowed, and out of the reach of children.
Never double-dose on tirzepatide, even if you’ve missed a dose.
If your side effects are severe or persistent, reach out to your GP or the healthcare professional who prescribed tirzepatide — they’re there to help you.
Tirzepatide Side Effects U.K.: In Summary
Tirzepatide is a safe and effective treatment for type 2 diabetes and weight loss. But, as with all medications, it can come with side effects.
Remember this:
The most common side effects of tirzepatide include mild stomach problems, fatigue, headaches, and injection site reactions.
These side effects are most common when you start tirzepatide or increase your dose. They usually go away within a few days or weeks.
More serious side effects may include pancreatitis, dehydration, or gallbladder problems.
For most people, tirzepatide is a safe and powerful tool for weight management.
To ensure your safety, always follow your healthcare professional’s guidance, review the patient information leaflet, report all side effects via the Yellow Card scheme (as this is a Black Triangle medicine), and attend regular monitoring appointments.
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FAQs
Find answers to commonly asked questions about tirzepatide side effects below.
What are the most common side effects of tirzepatide?
The most common side effects of tirzepatide are gastrointestinal. This includes nausea, constipation, diarrhoea, stomach pain, bloating, and loss of appetite.
What are tirzepatide long-term side effects?
Long-term side effects are still being studied. Current evidence suggests tirzepatide is generally safe, but monitoring is ongoing for risks like thyroid tumours, vision changes, and pancreatitis.
In general, the long-term side effects of rapid weight loss can include nutritional deficiencies or muscle loss. Eating a varied diet, rich in protein and nutrients, can help preserve muscle mass and maintain nutrient levels.
What should I do if I experience side effects of tirzepatide?
Contact your GP or private healthcare professional to discuss tirzepatide side effects. Seek immediate attention if you have symptoms of low blood sugar or an allergic reaction — although these side effects are less common, they’re serious. Report side effects via the MHRA Yellow Card scheme.
Are tirzepatide injection side effects different from other GLP-1 receptor agonists?
Not significantly. Like semaglutide (Wegovy®, Ozempic®) or liraglutide (Saxenda®), tirzepatide can cause nausea, constipation, and injection site reactions. Though studies suggest tirzepatide may be slightly more effective for weight loss than semaglutide.
Is tirzepatide authorised in the U.K.?
Yes, tirzepatide is authorised in the U.K. for treating type 2 diabetes and obesity. It’s authorised under the brand name Mounjaro®. Tirzepatide is sold as Zepbound® in the United States, but not yet in the U.K.
This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your GP about the risks and benefits of any treatment.