Mounjaro Side Effects

Mounjaro can cause a range of side effects. The most common ones are usually mild and temporary, but some rarer side effects can be more serious.

What are the common side effects?

‘Very common’ and ‘common’ side effects mean that they affect more than 1 in 10 or up to 1 in 10 people. They are not usually severe and should pass shortly after you have started taking Mounjaro.

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

• being sick (vomiting) – this usually goes away over time
• constipation
• feeling sick
• diarrhoea

When taking Mounjaro for type 2 diabetes, very common side effects also include signs of low blood sugar, such as:

• headache
• drowsiness
• weakness
• dizziness
• feeling hungry
• confusion
• irritability
• fast heartbeat
• sweating

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

• allergic reaction (rash, itching, eczema)
• feeling less hungry (more common in patients treated for type 2 diabetes)
• tummy pain
• indigestion and/or reflux or heartburn
• bloating
• burping and gas
• hair loss
• tiredness
• injection site redness or itching and general soreness
• fast pulse
• increased pancreatic enzymes (more for patients with type 2 diabetes)

In most patients, side effects go away or get less intense over time. They may reappear as you increase your dosage but once you’ve reached your maintenance dose they can die down. If you have any concerns about this before starting your treatment, you should speak with your doctor.

If you have any specific questions about any of the side effects listed and how they could affect you, you should also speak with your doctor or a pharmacist.

For more general information about common side effects of Mounjaro, take a look at the patient information leaflet that should come with the medication.

What are the mild side effects?

Some people experience mild side effects with Mounjaro, although this varies from person to person.

Mild, common side effects of Mounjaro include:

• injection site irritation
• feeling sick
• constipation
• diarrhoea
• heart burn

Mild side effects should get less intense over time and usually can be managed at home.

If you have any concerns about certain mild side effects that are listed, speak with your doctor or a pharmacist.

Injection site irritation

It’s common to experience irritation where you have been injecting Mounjaro, examples of this include:

• redness
• bruising
• swelling
• itching
• general pain

These flare ups should settle as your body gets used to taking the medication.

Feeling sick (nausea)

During clinical trials of Mounjaro, patients reported feeling sick typically as their dose was increased, but this usually improved over time. If you are bothered by this symptom for an extended period of time or it is starting to affect your day to day life, you should speak with your doctor or a pharmacist.

Constipation

Like with nausea, clinical trials show symptoms of constipation are typically reported by patients after an increase in dosage during weight-loss treatment with Mounjaro. This side effect should improve over time. However, if you have already tried managing your symptoms and constipation has become an issue in your daily life, speak with your doctor.

Diarrhoea

Diarrhoea is a common side effect when undergoing weight-loss management treatment with Mounjaro, and should get better after a few days. However, if your diarrhoea has lasted more than a week (7 days) or if you notice blood in your poo, speak with a doctor or pharmacist.

Heartburn

When being treated with Mounjaro you may experience heartburn, but it should be mild and temporary. Your doctor might recommend you take antacids for these symptoms. If they persist, you should speak with your doctor and they should advise according to your personal condition of health.

For information on managing mild side effects of Mounjaro, see the section on ‘How can I manage Mounjaro side effects?’.

What are the serious side effects?

Serious side effects of Mounjaro are uncommon (may affect up to 1 in 100 people) and rare (may affect up to 1 in 1,000 people).

Uncommon serious side effects:

• severe pain in the stomach and back which does not go away (acute pancreatitis)

Rare serious side effects that require immediate medical attention:

• breathing problems
• rapid swelling of lips, tongue and/or throat
• difficulty swallowing
• fast heartbeat

For more information on serious side effects, see the patient information leaflet, which should have come with the treatment.

Does Mounjaro cause hair loss?

In a clinical study for weight loss management, 4.7% of patients treated with Mounjaro reported hair loss. The events were mild and most patients recovered while they continued their treatment.

Does Mounjaro cause cancer?

In animal studies, there have been reports of thyroid c-cell tumours (a type of thyroid cancer) in mice who were given other medications in the same drug family. However, no human clinical trials have found an increased risk of cancer from using tirzepatide. If you are concerned about your risk of thyroid cancer, speak to a doctor.

Does Mounjaro make you tired?

Fatigue (feeling tired) is a common symptom of Mounjaro, but it should pass with time. If you have been taking Mounjaro and are bothered by persistent side effects such as tiredness, you must speak with your doctor.

Why does Mounjaro make you cold?

Whether or not you may experience coldness since taking Mounjaro will depend on your personal health condition. Some people who take Mounjaro experience feeling cold or having chills. If you are feeling cold since taking Mounjaro and it is bothering you or not going away, speak with your doctor. They should be able to advise you about your dosage.

Can Mounjaro cause body aches?

Body aches are not a known side effect of Mounjaro. You should speak with your doctor if you are experiencing any side effects that are not listed in the patient information leaflet.

You can report side effects not listed in your patient information leaflet via the Yellow Card reporting site.

Can Mounjaro cause depression?

There may be a link between depression and Mounjaro, however it is not known how likely Mounjaro is to cause depression.

If you already have been diagnosed with depression before starting your treatment with Mounjaro, or if you’re experiencing depression after starting your treatment, speak to your doctor. They may recommend an alternative weight-loss treatment or starting a separate treatment for depression.

Does Mounjaro cause erectile dysfunction?

Erectile dysfunction is not a known side effect of Mounjaro. If you’re experiencing symptoms of erectile dysfunction, we have a range of erectile dysfunction treatments available. Simply start a consultation and one of our doctors will review your health and symptoms accordingly. They will then prescribe you a treatment if necessary.

Does Mounjaro cause dehydration?

No, Mounjaro does not cause dehydration directly, but some gastrointestinal related side effects of Mounjaro can. In clinical studies, some patients have experienced side effects such as nausea, vomiting and diarrhoea which could lead to dehydration. Speak with your doctor if you have any concerns about the potential effects of Mounjaro.

How long Mounjaro side effects last is different for each person. There’s no set time they will last. You’re most likely to get side effects when you first begin to take Mounjaro, or when you increase the dose. This is why Mounjaro is prescribed through the process of a dosing schedule, so your body can safely get used to the medication.

Mild side effects are likely to go away between a few days to a couple of weeks as your body adjusts to the treatment.

More severe side effects can take longer to go away, so you should discuss these and any concerns you have with your doctor for advice and support.

If you stop taking Mounjaro, your side effects should go away. If you plan to stop taking Mounjaro, you should speak to your doctor first.

If you are worried about how long side effects may last before starting a treatment of Mounjaro, you should speak with your doctor and they will give you personalised advice.

When do Mounjaro side effects start?

If you experience side effects from your Mounjaro treatment, you will most likely get them when you begin the treatment or when you are increasing your dosage.

Can Mounjaro cause long-term side effects?

It is rare for Mounjaro to cause ongoing side effects. You must speak with your doctor as they may advise you to stop taking Mounjaro, if you experience:

• ongoing digestive issues
• pancreatitis (pain in the stomach and back that gets worse)
• ongoing vomiting

Side effects can get worse or come back when you increase your dose. Although you’ve already started Mounjaro, your body will still need to adjust to the next dosage level if you increase.

These side effects usually get better over time as your body adjusts. If you have any specific questions about this, you should raise your concerns with your doctor before you increase your dosage.

When starting treatment or moving onto a new higher dosage of Mounjaro, adjusting can be difficult. Fortunately, most mild side effects of Mounjaro can be managed at home.

Let’s explore some top tips to ensure you can handle your symptoms at home effectively and stay safe during your treatment.

Nausea (feeling sick) and/or vomiting

It’s fairly common to feel sick during your treatment with Mounjaro, particularly during periods of adjustment or at the very start of your treatment.

To improve your symptoms of sickness we recommend:

• staying hydrated – sipping cold drinks regularly should help with nausea and dehydration can increase side effect symptoms
• eating frequent small meals – stopping eating when you’re full and only eating small portions frequently will aid your digestive process and in turn should ease sickness
• getting fresh air – should distract you from your sickness and taking deep breaths may help you to feel the full benefit
• relaxing – do what you enjoy and try relaxing to distract yourself, for example listen to music
• avoiding fatty or greasy food – which can increase symptoms of nausea due to their richness
• eating bland foods – like crackers or toast, to help settle your stomach

If you experience nausea persistently and it begins to affect your daily life, speak with your doctor and they might recommend altering your dosage, or find an alternative to Mounjaro for the remainder of your weight loss treatment.

Heartburn

Heartburn is often experienced by patients undergoing weight-loss management treatment with Mounjaro. To ease this side effect, we recommend lifestyle changes that should ease heartburn, such as:

• avoiding certain food and drink like citrus or acidic foods, fatty or spicy foods, coffee and alcohol
• light physical exercise such as yoga, or stretching

We also recommend:

• checking in with yourself emotionally and finding ways to relax
• eating smaller, more frequent meals

When experiencing heartburn, it is best to avoid:

• eating within 3 to 4 hours of going to bed
• smoking
• wearing tight clothing

Sometimes heartburn can be related to another issue, such as stress and anxiety. Speak with your doctor or pharmacist if you are experiencing heartburn and it is not going away. They will be able to give you personalised advice. If you have already tried making lifestyle changes to alleviate your symptoms, they may recommend you take antacids.

Constipation

Constipation is a common side effect of Mounjaro, particularly for patients just starting the medication or during the stage where dosage is increased.

To manage constipation, we recommend that you make changes to diet and exercise and adjust your toilet routine.

Making changes to your diet and exercise routine

In order to be effective, Mounjaro should be prescribed in addition to a weight loss plan that includes lifestyle changes, such as adjusting your diet or following an exercise plan. These changes will also help in managing constipation as a side effect.

Speak with your doctor for more personalised advice on what approach you should take with nutrition to ensure the treatment is effective for you.

If you are experiencing constipation, these lifestyle changes may help improve it:

• eating a balanced diet (learn more on NHS Eatwell Guide)
• eating fruits containing sorbitol such as grapes, raisins, apricots, apples, raspberries, and strawberries
• gradually increasing the fibre in your diet
• including wheat bran, linseed or oats in your diet

Increasing your physical activity can help move food through your system. Even simply going for a walk can help.

If you have already made diet and nutritional changes and have not seen any effect on your constipation, speak with your doctor or a pharmacist. They may suggest a laxative, which can help.

If you have already tried laxatives and they haven’t helped with your symptoms, see your doctor if you:

• are regularly constipated
• are regularly bloated
• have blood in your stool (poo)
• feel tired all the time
• are taking medication that causes constipation (opioids)
• notice sudden changes in toilet habits
• have stomach pain

Adjusting your toilet routine

If you are struggling to go to the toilet, keep track of when you do and:

• try to go to the toilet regularly, at a regular time
• give yourself time to go
• when you need to go, do not delay it

We recommend raising your feet or putting your feet on a footstool when you are on the toilet if you are struggling to pass stools (poo).

Diarrhoea

If you are experiencing Diarrhoea, we recommend that you stay hydrated by drinking water, or another liquid if you prefer, like squash.

Try to avoid fatty or spicy foods as this may make your symptoms worse.

If your diarrhoea has lasted more than a week (7 days) or if you notice blood in your poo, speak with a doctor or pharmacist.

Headache

You may experience headaches as a result of your treatment with Mounjaro.

To help manage this symptom at home, we recommend you:

• drink plenty of fluids – to ensure you are hydrated
• avoid alcohol – which can make you more dehydrated
• speak with a pharmacist – who can advise you the right painkillers

If you find this symptom persists and affects your life, get in touch with your doctor.

Aches and pains – in the stomach, back, neck and joints

It is common to experience aches and pains in the stomach when taking Mounjaro. Especially around the sites where you are injecting.

However, less reported side effects are pain in the back, neck or joints. If you experience aches and pains in these areas and they persist, please contact your doctor.

In particular, speak with your doctor if you are experiencing:

• a lump or swelling in the neck
• pain in your back and stomach or a pain which begins in your stomach and ends at your back

Injection site reactions (e.g. bumps and itchiness)

You may find, particularly at the start of your treatment with Mounjaro, that where you have chosen to inject the medication feels sore, has bumps or it may be itchy. To help ease these symptoms, we recommend:

• ensure that you thoroughly clean the skin where you are injecting before you inject
• use an ice pack to numb the area before you inject so that you can prevent pain and irritation
• using antihistamines – taking antihistamine tablets or applying creams to the area affected
• changing where you inject – carefully read the ‘Instructions for Use’ for the Mounjaro pen to ensure you do this safely or speak with your doctor or pharmacist

If these symptoms persist, speak with your doctor.

Seek medical attention immediately, dial 999 or go to A&E, if you are experiencing serious (uncommon or rare) side effects of Mounjaro such as:

• inflamed pancreas – severe pain in the stomach and back which not go away
• symptoms of a severe allergic reactions – breathing problems, swelling of the lips, tongue and/or throat, difficulty swallowing and fast heart beat

If you have persistent but mild symptoms that are bothering you, speak with your doctor.

Some side effects of Mounjaro are often made worse by not following these lifestyle changes. When taking Mounjaro it is important you try to follow your doctor’s advice about your personal nutrition and exercise. The effectiveness of Mounjaro will also be reduced.

Two of the key things that will make side effects worse are fatty and greasy foods, and alcohol.

Fatty, greasy foods

Foods such as pizza, burgers, and chips are difficult for your digestive system to process. When taking Mounjaro, it is known that these foods can increase side effects if you have them.

Alcohol

There is no reported reaction between alcohol and Mounjaro but it is known to make side effects like indigestion, vomiting and nausea worse. Studies have shown that excessive alcohol consumption during tirzepatide treatment limits the efficacy of the medication.

Managing side effects worsened by fatty, greasy foods and alcohol can be done at home. The following should ensure swift recovery:

• keeping hydrated with water or squash
• staying active
• eating bland foods

If you have any particular questions about lifestyle changes and Mounjaro, you should speak with your doctor.

Your side effects should go away once you stop taking Mounjaro, but you should speak to your doctor first.

It takes around 25 days for Mounjaro to leave your system. The medication has a half-life of 5 days (meaning it will take your body 5 days to get rid of half of a dose).

If you are experiencing any side effects that you cannot manage at home within this timeframe, seek medical advice.