Mounjaro® side effects and how to manage them

Reviewed by Dr Bhavini Shah

Like any medication, Mounjaro (tirzepatide) can come with some side effects - a few of which are pretty common. The good news is that most of them are manageable and usually ease up over time. Keep reading to learn about the most frequent and rare side effects of Mounjaro, what to expect, tips for handling symptoms, and when it's a good time to chat with a healthcare professional.

In this article, you will:

• Get to know the common side effects of Mounjaro, how they might change over time, and when to ask for help.
• Find out what the timeline looks like for Mounjaro side effects, from day one to the first week and into long-term use.
• See how side effects can differ for non-diabetics, women, or when you're upping your dose.
• Learn how to manage or reduce side effects and know when it's time to talk to a doctor if things get serious.

Mounjaro side effects timeline: when do they start and how long do they last?

Many people notice side effects shortly after their first Mounjaro injection. These can begin as soon as a few hours after your dose, especially digestive symptoms.

First starting Mounjaro

According to Mounjaro’s patient information leaflet, certain side effects are most likely to appear when first starting your treatment. These symptoms include:

• Nausea or vomiting
• Diarrhoea or constipation
• Bloating, gas, or burping
• Tiredness or body aches
• Loss of appetite

After eating

Some people feel nausea or discomfort after meals. This is a common side effect of Mounjaro due to how it slows digestion. Eating smaller, lighter meals can help reduce these symptoms.

How long do Mounjaro side effects last?

For many, these symptoms ease up after 2 to 4 weeks. However, Mounjaro long-term side effects can include ongoing digestive changes or fatigue. If side effects continue or worsen, especially after increasing your dose, speak with a healthcare provider.

"Gradual dose increases and staying well-hydrated can help reduce side effects. Don't skip meals and avoid greasy or spicy foods early on.” - Dr Bhavini Shah

Do different genders experience different side effects?

There is currently no evidence that side effects for Mounjaro will differ depending on your gender.

Common side effects of Mounjaro

Like many medications, Mounjaro can come with some side effects, but most are mild and temporary. Some of the most common Mounjaro side effects in the UK and around the world include:

• Nausea or vomiting
• Constipation or diarrhoea
• Burping, bloating or indigestion
• Loss of appetite
• Tiredness or low energy
• Mild stomach pain
• Headache

You might notice some symptoms during the first few weeks of starting treatment or if you increase your dosage, like when you move up to 5 mg of Mounjaro or more. Most people find these effects do get better as their body adjusts to the medication.

How to manage common Mounjaro side effects

The good news is that there are simple ways to help reduce or even avoid many of the common side effects of Mounjaro. Whether you're dealing with nausea, digestive issues, or fatigue, there are lots of things you can do to help. Below, we break down the most frequently reported symptoms and how to handle each one.

Mounjaro and nausea

Nausea is one of the most common Mounjaro injection side effects, especially in the early weeks or after a dose increase. This is because Mounjaro slows down digestion so that you feel full faster. This can also trigger queasiness, especially after eating large or rich meals.

Tips to manage nausea:

• Eat small portions but often
  
• Bland foods like rice, toast, bananas or crackers will help
• Avoid eating greasy, spicy or heavy foods
• Sip water or ginger tea slowly
• Try eating cold or room-temperature foods, which may feel gentler

Mounjaro and diarrhoea

Side effects like diarrhoea can start soon after your first dose and may come and go over the first few weeks. It’s often linked to changes in digestion and how your gut processes food.

Tips to manage diarrhoea:

• Stay hydrated with water or oral rehydration drinks
  
• Avoid caffeine, alcohol and high-fat foods
• Try low-fibre foods like white rice, plain chicken or dry toast
• Take note of any trigger foods and avoid them temporarily

Mounjaro and constipation

Some people experience diarrhoea, but others find Mounjaro causes constipation, especially after using it for a few weeks.

Tips to manage constipation

• Drink more water (aim for 6-8 glasses a day)
  
• Eat oats, berries or prunes and other gentle fibres
• Keep active as much as you can (even short walks can help stimulate digestion
• Consider a mild over-the-counter laxative (but check with your pharmacist first)

Mounjaro and fatigue

Feeling tired or low on energy is a common Mounjaro weight loss side effect, especially during the first week or two. This can be due to not staying hydrated, eating less or changes in blood sugar levels.

Tips to manage fatigue:

• Try to eat regularly, even if it's just small portions
  
• Don't forget to drink plenty of water
• Make sure you're getting enough sleep
• Avoid skipping meals

Mounjaro and gas / burping

Burping, gas, or bloating after starting Mounjaro is a common side effect. These happen as your digestion slows down and food stays in your stomach for longer.

Tips to help manage burping and gas:

• Eat slowly and chew thoroughly
• Avoid fizzy drinks or chewing gum
• Limit high-fibre or gassy foods like beans, cabbage or onions
• Avoid lying down immediately after meals

Mounjaro and changes in appetite

One of the goals of Mounjaro is to reduce appetite, but for some people, the drop in hunger can feel drastic or uncomfortable.

Tips to help manage loss of appetite:

• Eat small meals and often, even if you're not hungry
  
• Choose nutrient-rich foods like avocados, nuts and protein shakes
• Avoid skipping meals to support stable energy and blood sugar

Mounjaro and hair loss

A side effect reported is hair thinning or hair loss on Mounjaro, usually after several weeks or months. Although this is not directly caused by the medication, rapid weight loss or reduced calorie intake may play a role.

Tips to help manage hair loss:

• A diet high in protein and iron
  
• Talk to your GP about supplements (like biotin or zinc)
• Avoid tight hairstyles or heat styling
• Consider speaking with a dermatologist if shedding continues

Mounjaro and headaches

Headaches can happen during the adjustment period and may be related to dehydration, changes in blood sugar levels, or a decrease in food intake.

Tips to help manage headaches:

• Drink plenty of water throughout the day
  
• Eat balanced meals that include enough carbohydrates
• Avoid skipping meals
• Take a nap in a quiet, dark room if a headache begins

Rare side effects of Mounjaro

Although rare, there are some more serious Mounjaro injection side effects that may require medical attention. These are not experienced by most people, but it's important to know what to look out for.

Mounjaro and pancreatitis

Pancreatitis is an inflammation of the pancreas. Although it’s rare, it can happen while taking weight loss medications like Mounjaro.

Keep an eye out for these signs:

• Intense stomach pain
• Pain that spreads to your back
• Vomiting and fever
• Pain that gets worse after meals
• If you notice any of these symptoms, seek urgent medical care

Mounjaro and thyroid issues

In some animal studies, Mounjaro has been linked to a higher risk of thyroid C-cell tumours. There’s no real proof of this happening in humans, but it's something to keep in mind, especially if you or anyone in your family have had thyroid cancer. Watch out for:

• A lump or swelling in your neck
• Trouble swallowing
• Hoarseness or voice changes
• A sore throat that won't go away

Mounjaro and mental health side effects

Some people have mentioned feeling low, anxious, or emotional while taking Mounjaro. These are quite rare, but they can affect how you feel day-to-day, so if you find yourself feeling this way, talk to your doctor.

What to watch out for:

• Mood swings
  
• Feeling anxious or nervous
• Feeling unusually down or withdrawn

Mounjaro and vision changes

Some people have reported blurry vision after using Mounjaro. This could be linked to changes in blood sugar levels, especially for those with diabetes. GLP-1 treatments like Mounjaro can affect thirst cues as well as appetite, which can lead to dehydration, dry eyes and blurry vision as a result.

Eye problems like diabetic retinopathy, Non-arteritic anterior ischemic optic neuropathy (NAION) and Neovascular age-related macular degeneration (wet AMD) have been reported in users taking GLP-1 treatments, though these numbers were relatively low:

• In a Mounjaro clinical study ≤1% of new diabetic retinopathy events happened while treatment occurred (though the study didn’t include patients who already had moderate or severe retinopathy)
• A study of GLP-1 treatments showed NAION in 0.04% of users compared to 0.02% taking different diabetes treatment, though this included semaglutide (the main ingredient in Wegovy) alongside tirzepatide (the main ingredient in Mounjaro)
• In a clinical study, Wet AMD was diagnosed in 0.2% of GLP-1 users compared to 0.1% of non-users. However, this was a retrospective study so could not prove that wet AMD was caused by GLP-1 treatment.

What to watch for:

• Blurry or double vision
  
• Trouble focusing
• Sudden changes in eyesight

Always consult a healthcare professional if your vision is affected.

Other rare or serious side effects may include:

• Skin rash or itching, which may indicate an allergic reaction
• Gallbladder issues, including pain in the upper right side of the stomach
• Urinary changes, such as difficulty urinating or increased urgency
• Severe or persistent vomiting, which poses a risk of dehydration
• Signs of low blood pressure or fainting, particularly if you are not eating regularly

Will side effects change when I change dose?

Yes, side effects often change when you adjust your dose. According to clinical studies shared by Mounjaro’s manufacturer, Eli Lilly, most nausea, vomiting, and diarrhoea occurred during dose increases, especially when moving from lower doses to maintenance levels like 5mg, 10mg, or 15mg.

The good news? These symptoms usually become less frequent and less severe over time as your body adjusts to each dose. That's why it’s important to follow the step-up dosing plan provided by your healthcare provider, it helps minimise discomfort and improve long-term tolerance of the medication.

Mounjaro long-term side effects

So far, there is no evidence of negative long-term side effects linked to Mounjaro at its highest recommended maintenance dose, according to current data. Researchers continue to monitor long-term use as the medication becomes more widely used.

Reported long-term benefits may include:

• Sustained weight loss
• Lower blood glucose levels
• Improved insulin sensitivity
• Reduced appetite and food cravings
• Lower risk factors for heart issues like blood pressure and cholesterol

Although benefits sound great, it's also good to keep in mind that some short-term side effects can lead to longer-term health issues if not managed properly. For example:

• Ongoing vomiting or diarrhoea may lead to dehydration, so it’s important to stay hydrated
• If you’re feeling fatigued for a long time, it might be a sign that you need to focus on your nutrition or eating enough
• Noticing changes in your mood is important; ignoring them could impact your mental well-being over time

What if I get a side effect that isn't listed?

While we've covered the most common Mounjaro side effects, everyone's experience is different. If you notice a new or unexpected symptom, it's' important not to ignore it. Some reactions might be unrelated, but others could signal your body needs extra support.

You can report any suspected side effects to the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk. Always contact your GP or 111 if a symptom feels severe, persistent, or concerning, especially if it affects your ability to eat, hydrate, or carry out daily activities.

"Unusual side effects don't always mean you have to stop treatment, but they should always be taken seriously. It’s important to reach out to your healthcare provider to rule out anything more serious." - Dr Bhavini Shah

Does drinking alcohol make the side effects worse?

Drinking alcohol while on Mounjaro may increase your risk of digestive side effects like nausea, vomiting, or diarrhoea. Alcohol can also affect your blood sugar, especially if you're eating less than usual. If you choose to drink, do so in moderation and avoid it during your first few weeks or after a dose increase.

Will Mounjaro side effects go away on their own?

For most people, yes, Mounjaro side effects like nausea, bloating, or tiredness ease up over time. Your body needs a bit of time to adjust to the changes in digestion and appetite. Most symptoms improve within the first few weeks, especially if you're following recommended lifestyle tips and increasing doses gradually.

If your symptoms persist or affect your daily life, speak to your GP. They may suggest adjusting your dose, timing, or switching to a different medication.

Do you get withdrawal symptoms when you stop taking Mounjaro?

Mounjaro isn't known to cause physical withdrawal symptoms like traditional addictive substances. However, you may notice changes in appetite, digestion, or weight regulation if you decide to stop suddenly instead of gradually.

If you're coming off Mounjaro, it's best to do so under medical guidance. Your clinician can help you taper the dose gradually and support your weight and blood sugar management in other ways.

Mounjaro and cancer

At the moment, there's no confirmed evidence that Mounjaro causes cancer in humans. In some early studies on animals, some thyroid tumours were seen in rats treated with medications like Mounjaro (tirzepatide). Because of this, people with a history of certain types of thyroid cancer or multiple endocrine neoplasia syndrome type 2 (MEN 2) are usually advised not to take Mounjaro.

Research in humans is ongoing. If you have a personal or family history of thyroid conditions, speak to your doctor before starting treatment. And if you ever notice a lump in your neck, hoarseness, or trouble swallowing, get it checked as soon as possible.

Mounjaro and mental health

Although it's not spoken about often, some people taking Mounjaro have noticed changes in their mood, increased anxiety, or even feeling depressed. These emotions could be linked to changes in energy, appetite, or hormones, especially during the first few weeks of treatment or with rapid weight loss.

If you feel persistently low, anxious, or not like yourself, it's important to speak to your GP or mental health provider. There's plenty of support available, and you don't have to go through it alone. It's perfectly okay to ask for help.

"Even if mental health symptoms feel mild at first, they deserve attention. Rapid changes in weight or routine can be triggering for some people. Let your healthcare provider know if your mood starts to shift, early support makes a big difference." - Dr Bhavini Shah

When to seek medical advice regarding your side effects

Most Mounjaro side effects are mild and improve over time, but if something doesn't feel right, contact your GP, pharmacist, or call at NHS 111 if you notice any of these:

• Your side effects are severe or getting worse
• You're unable to keep fluids or food down
• You experience sudden stomach pain, blurred vision, or skin changes
• You notice signs of depression, mood swings, or anxiety
• You feel faint, dizzy, or confused

In rare cases, side effects could signal something more serious, like pancreatitis, gallbladder issues, or thyroid changes. When in doubt, always reach out.

References

https://www.medicines.org.uk/emc/files/pil.14203.pdf
https://www.lilly.com/news/media/media-kits/mounjaro
https://www.mounjaro.com/how-to-use-mounjaro#possible-side-effects
https://www.yourhormones.info/hormones/calcitonin/
https://www.nhs.uk/conditions/acute-cholecystitis/
https://www.macmillan.org.uk/cancer-information-and-support/stories-and-media/blogs/weight-loss-injections-and-cancer
https://www.ncbi.nlm.nih.gov/books/NBK555956/
https://www.sciencedirect.com/science/article/pii/S0278262618304597
https://medical.lilly.com/us/products/answers/what-is-the-incidence-of-diabetic-retinopathy-in-people-with-type-2-diabetes-t2d-receiving-mounjaro-tirzepatide-114176
https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2837377
https://www.nhs.uk/conditions/low-blood-sugar-hypoglycaemia/
https://jamanetwork.com/journals/jamaophthalmology/article-abstract/2834964