Mounjaro Side Effects

According to the patient information leaflet that comes with your medication, the side effects when taking Mounjaro (tirzepatide) for weight loss include:

Very common side effects

• feeling sick (nausea)
• being sick (vomiting)
• diarrhoea
• constipation

These side effects may affect more than 1 in 10 people but usually aren’t severe. If they become severe, speak to your doctor straight away. They may recommend stopping treatment, especially if you’re at risk of dehydration or severe constipation.

Common side effects

• allergic reactions (hypersensitivity), such as eczema, rash or itching
• dizziness
• low blood pressure (hypotension)
• stomach pain
• indigestion
• burping
• gas
• bloating of the stomach
• heartburn or reflux (gastroesophageal reflux disease or GORD)
• hair loss
• tiredness
• injection site reactions, such as redness or itching
• an increased levels of certain pancreatic enzymes, such as lipase, in the blood

These side effects may affect up to 1 in 10 people taking Mounjaro injections. If you get any of these side effects and they aren’t getting better after a few weeks, or become severe, speak to your doctor straight away.

Uncommon side effects

• fast pulse
• an increased levels of certain pancreatic enzymes, such as amylase, in the blood
• gallstones – most of the time gallstones don’t cause symptoms until they cause a blockage. Symptoms of a blockage include sudden and severe stomach pain that can last a few hours or a few minutes and confusion, fever, and chills
• pain at the injection site
• an increased level of calcitonin in the blood
• cholecystitis (infection of the gallbladder) – symptoms include a sudden sharp pain in the upper right side of your stomach that may spread towards your shoulder, fever and jaundice

These side effects may affect up to 1 in 100 people and can be more serious, so if you get any of these, speak to your doctor straight away. If you think you’ve got gallstones or cholecystitis and can’t get in touch with your GP, call 111 or get to A&E, as these usually need to be treated at the hospital.

Serious side effects

• Uncommon (may affect up to 1 in 100 people): An inflamed pancreas (acute pancreatitis) which can cause long-lasting and severe pain in the stomach and back.
• Rare (may affect up to 1 in 1,000 people): A severe allergic reaction (anaphylaxis or angioedema) which can cause problems breathing, swelling of the face and lips, and difficulty swallowing.

See a doctor straight away or go to A&E if you think you’ve got an inflamed pancreas.

Studies into taking the highest maintenance dose of Mounjaro (15mg) for 72 weeks didn’t find any negative long-term side effects. In fact, the long-term effects of taking tirzepatide included:

• reduced blood pressure for those with high blood pressure
• weight loss
• lower blood glucose (sugar) levels in people with type 2 diabetes

Still, some side effects may cause long-term health problems if not addressed early:

• acute pancreatitis – Although this can be treated, studies into acute pancreatitis show that around 25% of people may get it again. Your doctor may suggest that you stop taking Mounjaro if you get pancreatitis while taking it to prevent this.
• dehydration caused by severe vomiting and diarrhoea – If you get these symptoms, drink lots of fluids and speak to your doctor, especially if it lasts more than 48 hours. Being dehydrated could impact how well your kidneys work and in severe cases, may cause kidney failure.

There are some reports online that Mounjaro may pose a risk of developing thyroid cancer. In human clinical trials, cancer has not been found to be a side effect of taking Mounjaro.

These claims come from a study of tirzepatide on male and female rats over 2 years. This study found that tirzepatide, when injected twice weekly in rats, caused an increase in thyroid C-cell tumours (adenomas and carcinomas) in all doses. It’s important to note here that rats are highly susceptible to developing cancers and tumours and this doesn’t mean that humans taking Mounjaro are necessarily at an increased risk of cancer.

In another 6 month study on mice with twice-weekly tirzepatide injections, there were no cases of thyroid C-cell hyperplasia (an abnormal change of cells) or neoplasia (abnormal growth of cells).

In other studies, like one investigating tirzepatide and cancer rates, Mounjaro and other GLP-1 receptor agonists have been linked to a reduction in some cancers, especially ones linked to high blood glucose levels, diabetes and obesity.

You should not take tirzepatide (Mounjaro) if you don’t meet the prescribing requirements, which is either a body mass index (BMI) of:

• 30 or more (obesity), or
• at least 27 but less than 30 (overweight) and one or more weight-related health problems, including prediabetes, abnormal levels of fats in the blood, high blood pressure, obstructive sleep apnoea, or a history of stroke, heart attack or blood vessel problems

You also shouldn’t take it if you:

• have an allergy to tirzepatide, or any other ingredients in the Mounjaro pen
• are pregnant or planning to become pregnant
• are breastfeeding
• are under 18

Some health conditions could impact your use of Mounjaro, but your doctor may decide it’s still safe with closer monitoring. This depends on the severity of your condition and includes:

• severe problems with digesting food or food remaining in your stomach for longer, such as severe gastroparesis – it’s unlikely that you’ll be able to use Mounjaro as it could worsen these conditions.
• pancreatitis – if you’ve had it in the past and it’s never re-occurred, your doctor may decide it’s safe with closer monitoring. If you’ve had it very recently or have chronic pancreatitis, Mounjaro may not be suitable.
• certain eye problems, such as diabetic retinopathy or macular oedema – Mounjaro could worsen these conditions, so your doctor will let you know whether Mounjaro is suitable depending on the severity of your eye condition.
• type 2 diabetes – some medications that are regularly taken for blood sugar regulation, such as sulphonylurea or insulin, when taken alongside Mounjaro could cause low blood sugar (hypoglycaemia). Your doctor may want to change the doses of your other medications before starting Mounjaro, alongside closer blood sugar monitoring.
• liver or kidney disease – Mounjaro injections also contain benzyl alcohol*, which, in large amounts, can build up in your system and cause metabolic acidosis (too much acid in your body).

*Benzyl alcohol can also cause allergic reactions.

Most Mounjaro side effects start when you first begin your treatment. As you follow the Mounjaro dosage schedule and increase your dose, you may also get side effects when your dose is increased, as your body needs to get used to a higher dose of the medication.

That being said, some side effects could start at any time, such as injection site pain (uncommon), gallstones (uncommon) and an increased level of pancreatic enzymes in the blood (common).

Most Mounjaro side effects last a few days to a few weeks. You should let your doctor know straight away if your side effects are getting worse instead of better, are severe, or are affecting your daily life and preventing you from doing your normal activities. If they’re tolerable, there are ways to manage most side effects at home (see ‘Managing Mounjaro side effects’).

Most of the time, Mounjaro side effects will go away and get better on their own. In some patients, side effects go away when staying at a lower dose, so your doctor may recommend this. Although it’s not common, some patients don’t tolerate Mounjaro and need to switch to another weight loss medication.

If you get Mounjaro side effects, this doesn’t mean you can’t tolerate the medicine. More than 1 in 10 people may get very common side effects, like nausea or diarrhoea.

Luckily, there are ways to manage side effects at home so they don’t interfere with your daily life too much. Knowing how to manage Mounjaro side effects can help you get past them, so you can continue with your treatment and reach your weight loss goals.

Very common side effects

Mounjaro diarrhoea

Diarrhoea can be treated by:

• drinking plenty of fluids (mainly water or electrolyte drinks like Diarolyte)
• avoiding spicy, rich, fatty, and greasy foods
• avoiding caffeine, pure fruit juices, or alcohol (these could have laxative effects)
• using over-the-counter medicine, such as loperamide – most people only need it for 1 or 2 days and you shouldn’t take it for longer than 48 hours without speaking to your doctor
• resting and not over-exerting yourself

When you start to feel better, eat small portions of plain food and slowly introduce foods back if you don’t get more diarrhoea. Re-introducing food too quickly may upset your stomach, so take it slow. Just keep hydrated, as severe or long-lasting diarrhoea can cause dehydration. If you get severe diarrhoea, speak to your doctor.

Mounjaro sickness

This is a term used to cover Mounjaro nausea and Mounjaro vomiting, which are mainly treated the same way.

Nausea and vomiting can be treated by:

• drinking small amounts of fluid often (mainly water or electrolyte drinks)
• eating small, plain meals, if you can
• avoiding rich, fatty, or greasy foods
• avoiding caffeine, sugary drinks, or alcohol
• avoiding smoking, if you smoke, especially on an empty stomach
• getting fresh air
• resting
• distracting yourself when you feel nauseous to try and get your mind off of it, such as reading or watching your favourite TV show
• using over-the-counter or prescription medicines, such as anti-sickness tablets, after speaking with a pharmacist or doctor
• taking your Mounjaro dose with food, as this may alleviate some of the symptoms

As with diarrhoea, introduce foods back slowly as you start to feel better. Severe vomiting can cause dehydration, so speak to your doctor if you’re being sick frequently and can’t keep anything down.

Mounjaro constipation

Constipation can be treated by:

• eating little and often, so you aren’t putting too much into your stomach at once if you already feel uncomfortable
• eating a healthy, balanced diet
• avoiding alcohol
• choosing high-fibre foods or foods that may act as a natural laxative, such as broccoli, dried fruit, carrots or beans
• trying a stool softener or laxative which can be found over the counter
• doing stretches or other gentle exercises like walking
• trying to use a low stool while on the toilet, and if possible, raising your knees above your hips

If your constipation isn’t getting better with lifestyle changes and treatment, speak to your doctor. Severe constipation (not being able to pass a stool for longer than 3 days) can be painful and you may need prescription laxatives or another medication to help.

In rare cases, bowel obstruction could occur. This is a medical emergency and you should call 999 straight away. Symptoms include bloating, stomach pain, cramping, swelling, vomiting, difficulty passing gas, fever and loss of appetite.

Common side effects

Mounjaro burping

Burping can be treated by:

• not eating too quickly
• not using a straw or smoking, if you smoke (these can cause more air to enter your stomach)
• avoiding alcohol or fizzy drinks
• avoiding high-sugar, high-fat, or greasy foods
• drinking plenty of water
• trying mild to moderate exercise like walking, jogging, or yoga
• drinking herbal teas, such as peppermint
• taking Mounjaro with food
• using an over-the-counter remedy for indigestion, as this could be causing the gas in your stomach

Burping a lot on Mounjaro could be a sign of indigestion, heartburn, or acid reflux. If it keeps happening, speak to your pharmacist or doctor about a treatment for reflux that can be taken alongside Mounjaro. It may also help to keep a food diary, so you can see if any foods worsen your symptoms.

Mounjaro heartburn or reflux

Heartburn or reflux (GORD) can be treated by:

• eating small, more frequent meals
• avoiding foods and drinks that trigger your symptoms, which may include caffeine, alcohol, and spicy, fatty, acidic, or greasy foods
• sleeping with your head slightly raised (to stop acid travelling back up)
• avoiding laying down after eating or eating close to bedtime
• eating your food slowly and chewing thoroughly
• wearing comfortable, loose clothes
• stopping smoking, if you smoke
• trying an over-the-counter acid reflux or heartburn medication

If your symptoms don’t get better and you’re taking over-the-counter medication every day, speak with your doctor. They may prescribe a different treatment that could help more.

Mounjaro tiredness

Mounjaro may cause tiredness by itself, or other side effects may make you feel tired, especially if they’re preventing you from getting quality sleep.

Tiredness can be treated by:

• maintaining a healthy, balanced diet with plenty of nutrients
• taking multivitamins if you’re not getting all the nutrients you need from your diet and are deficient
• staying hydrated
• getting regular exercise – even though it’s hard to exercise when you feel tired, do what you can, as exercising can improve your energy levels
• maintaining a good sleep schedule (at least 8 hours each night)
• cutting down on screen time close to bed
• limiting caffeine intake, especially after midday
• avoiding alcohol
• getting plenty of rest in the day if you’re feeling run down, especially if you have other side effects

If you keep feeling tired on Mounjaro, speak with your doctor. They may want to check this isn’t caused by a lack of certain vitamins or minerals, such as Vitamin D or iron.

You can also feel tired when eating less, exercising more, and changing your diet, so being tired could be caused by these lifestyle changes.

Mounjaro dizziness

Dizziness can be treated by:

• drinking plenty of fluids
• lying down until it passes, then getting up carefully and slowly
• avoiding driving or using heavy machinery if you feel dizzy to prevent accidents
• getting enough rest
• avoiding stressful situations and finding ways to reduce your stress levels, as this could be contributing to your dizziness
• taking Mounjaro after food and drink, especially if you get dizzy right after your injection

Mounjaro is most likely to cause dizziness if your blood sugar levels are low (hypoglycaemia), although you can get dizziness as a side effect with normal blood sugar levels. If you get dizziness when taking Mounjaro, especially if you have other symptoms like headache, weakness, or irritability, speak with your doctor so they can check your levels. People with type 2 diabetes should take special care, as Mounjaro can increase the risk of hypoglycaemia if taken with insulin.

Mounjaro stomach pain

Stomach pain can be treated by:

• eating a balanced, healthy diet
• avoiding foods that could be triggering, such as oily, greasy, acidic, spicy, or rich meals
• eating little and often, instead of eating a lot at once
• using a hot water bottle or painkillers to help with the pain
• speaking with a pharmacist about other treatments that may help, as stomach pain could be caused by nausea or acid reflux

Stomach pain shouldn’t last long with Mounjaro and could be caused by other side effects. If you get severe stomach pain that isn’t going away, it could be a sign of something more serious, such as pancreatitis. Speak with your GP, call 111, or go to A&E if your stomach pain is severe and long-lasting.

Mounjaro injection site reaction

Injection site reactions can be treated by:

• using an antihistamine if the site feels itchy (a tablet or cream)
• switching up your injection site each week – either use the other side of the body or make sure you use a different area of skin each time
• making sure the area is fully clean before injecting
• always using a new, unbent needle
• using an ice pack to numb the site before injecting to reduce any pain, or afterwards to reduce inflammation

If following these instructions doesn’t help, or the reactions are severe, speak with your doctor.