Mounjaro Side Effects: What They Are & How To Manage Them

Mounjaro is an injectable GLP-1 medication containing the active ingredient tirzepatide. Its active ingredient mimics the two hormones glucagon-like peptide 1 (GLP-1) and gastric inhibitory polypeptide (GIP) that aid weight loss by reducing appetite and slowing down the rate of gastric emptying in order to increase feelings of fullness.

Like all treatments, Mounjaro may cause side effects that occur differently from person to person. If you've recently started or are considering starting to take Mounjaro for weight management, it is important to be aware of these side effects and how to manage them. Read our clear, easy-to-understand guide to potential side effects, how long side effects might last and how to manage them, so you can get the most out of your treatment with Mounjaro.

Managing Mounjaro side effects

Very common side effects (may affect more than 1 in 10 people)

These side effects are usually not severe. They are most common when first starting your course of Mounjaro, but usually subside over time.

• Feeling sick (nausea)
• Diarrhoea
• Being sick (vomiting)
• Stomach (abdominal) pain
• Constipation
• Low blood sugar (hypoglycaemia) when tirzepatide is used for type 2 diabetes with metformin and other diabetes medications. Symptoms of low blood sugar may include headache, drowsiness, weakness, dizziness, feeling hungry, confusion, irritability, fast heartbeat and sweating. Your doctor should tell you how to treat low blood sugar.

It is important to be aware that diarrhoea or vomiting can lead to dehydration, which may be serious. Make sure to stay hydrated during your treatment and contact your GP or doctor if you experience these symptoms.

Common side effects (may affect up to 1 in 10 people)

• Allergic reaction (hypersensitivity) (e.g. rash, itching and eczema)
• Dizziness
• Low blood pressure
• Feeling less hungry (decreased appetite)
• Indigestion (dyspepsia)
• Bloating of the stomach
• Burping (eructation)
• Gas (flatulence)
• Reflux or heartburn (also known as gastroesophageal reflux disease or GORD) - a disease caused by stomach acid coming up into the tube from your stomach to your mouth
• Hair loss
• Feeling tired (fatigue)
• Injection site reactions (e.g. itching or redness)
• Increased calcitonin levels in blood
• Increased levels of pancreatic enzymes such as lipase in the blood
• Gallstones
• Low blood sugar (hypoglycaemia) when tirzepatide is used for type 2 diabetes with metformin and other diabetes medications. Symptoms of low blood sugar may include headache, drowsiness, weakness, dizziness, feeling hungry, confusion, irritability, fast heartbeat and sweating. Your doctor should tell you how to treat low blood sugar.

Uncommon side effects (may affect up to 1 in 100 people)

• Low blood sugar (hypoglycaemia)
• Injection site pain
• Cholecystitis (infection of the gallbladder)
• Changed sense of taste
• Increased levels of pancreatic enzymes such as amylase in the blood
• Fast pulse
• Change in skin sensation
• A delay in the emptying of the stomach

Serious and uncommon side effects (may affect up to 1 in 100 people)

• Inflamed pancreas (acute pancreatitis) - symptoms may include severe and long-lasting pain in your stomach (the pain may move to your back). Seek immediate medical attention if you experience any of these symptoms.

Serious and rare side effects (may affect up to 1 in 1,000 people)

• Severe allergic reactions (e.g. anaphylactic reaction, angioedema). Seek immediate medical attention and inform your doctor straight away if you experience symptoms such as breathing problems, swelling of face, lips, tongue, and/or throat with difficulty swallowing, wheezing, fast heartbeat, pale and cold skin and feeling dizzy or weak.

More information about the side effects of Mounjaro can be found in its patient information leaflet, and its prescribing information^[1,2].

Mounjaro frequently asked questions

How long do Mounjaro side effects last?

For most people, the most common side effects of Mounjaro tend to be most noticeable when starting the medication or when the dose is increased.

Your body needs time to adjust to the new medication, and this adjustment period can vary from person to person. Often, these side effects begin to subside within a few weeks of consistent use.

Some individuals might find that certain side effects, like decreased appetite, continue to persist as they are part of Mounjaro's mechanism of action.

Will the side effects worsen when increasing the Mounjaro dose?

Mounjaro is typically started at a lower dose and gradually increased over time. This approach, known as dose titration, is designed to help your body adapt and minimise side effects.

However, it's common to experience a temporary return or intensification of side effects each time your dose is increased. For information about how to inject Mounjaro safely and correctly, see our expert's guide on administering Mounjaro.

Just like with taking a first dose of Mounjaro, your body needs to re-adjust to the higher concentration of the medication when your dose increases. This period of heightened side effects is usually brief and often resolves as your body becomes accustomed to the new dose.

When should I speak to a doctor about my side effects?

You should speak to your doctor if:

• Your common side effects are severe, don't improve over time or significantly impact your quality of life.
• You experience any of the less common or serious side effects mentioned above. Seek immediate medical attention if you experience serious side effects.
• You have new or worsening symptoms that concern you.
• You are considering a new weight loss treatment or planning to stop taking Mounjaro due to side effects. Never stop taking your medication without consulting your doctor.

Your doctor can offer personalised advice, adjust your dose, or explore alternative strategies to help manage your side effects.

Will I get withdrawal symptoms when I stop taking Mounjaro?

Mounjaro doesn't typically cause “withdrawal symptoms” in the way some other medications might.

However, if you stop taking Mounjaro, the beneficial effects of the medication can wear off. If you were taking it for weight management, your appetite might increase and lead to weight gain.

If you are considering stopping your treatment with Mounjaro, it is important to discuss this with your doctor so they can advise you about the best way to transition off the medication and manage any adverse effects.

Can Mounjaro cause hair loss?

Clinical trials suggest a small proportion of patients experience telogen effluvium, disrupting the normal hair growth phase and causing hair shedding.

While hair loss is listed as a common side effect of Mounjaro, the direct cause of hair loss is the actual weight loss rather than Mounjaro.

Is it normal to lose your appetite completely?

While Mounjaro does decrease appetite, a complete loss of appetite that prevents you from eating adequately is not typical and should be discussed with your doctor.

Can I drink alcohol while taking Mounjaro?

It's generally advisable to limit alcohol consumption while taking Mounjaro, as alcohol can affect blood sugar levels and potentially worsen some gastrointestinal side effects. Always consult your doctor for personalised advice on alcohol intake.

What if I miss a dose and experience side effects?

Missing a dose doesn't typically cause side effects in itself, but it can disrupt your body's adjustment to the medication. If you miss a dose, refer to your prescribing information or contact your doctor for guidance on when to take your next dose. Do not take two doses to make up for a missed one.

For more information about taking Mounjaro safely and effectively, see our guide on How to Take Mounjaro® Injections.