You’ve probably heard of the results it can drive, but do you know much about the side effects of Mounjaro?
Of the weight loss injections currently available in the UK, Mounjaro is considered the most potent. And while it works very well, it can also bring on symptoms like nausea and diarrhoea. Most of the time though, these aren’t anything to worry about and will clear up on their own.
As with all medications, side effects are a normal and expected part of the journey, and so we anticipate that most patients will experience side effects to some degree.
The good news however, is that this doesn’t need to disrupt your weight loss journey. Studies indicate that when starting out, around 15% of people experience some nausea on Mounjaro, however, at Voy, less than 1% of our patients cancel due to side effects.
So, what might you expect when taking Mounjaro, and how should you deal with any side effects that come up? We’ve got you—read on to find out.
Most common side effects of Mounjaro
Because of the medicine’s effect on the stomach, the most common side effects are gut-related. These include:
- Burping and flatulence
- Constipation
- Diarrhoea
- Gastrointestinal discomfort
- Nausea
- Vomiting
Other common symptoms are:
- Dizziness
- Hair loss
- Low blood pressure
- Lethargy
- Feelings of malaise
- Injection site reactions like irritation, itching and bruising
Side effects tend to come on when you first start Mounjaro or increase your dose. And usually, they go away in a matter of days or weeks.
Because everyone is unique, we can’t say whether you’ll be more likely to experience symptoms than someone else—nor which ones you’ll get. But nausea, diarrhoea, stomach pain, and constipation are the most frequently reported. They may affect over one in 10 people.
FYI: whether you’re using Mounjaro for weight loss or type 2 diabetes, studies show that both groups experience side effects similarly. Gut-related symptoms had a similar incidence in either camp—while overall, just 3-7% of people with and without diabetes stopped taking Mounjaro due to side effects.
Side effects support at Voy
"At Voy, this number is significantly lower - less than 1%. We offer loads of support for managing and treating your side effects, and if you’re ever concerned, you can hop on the phone to our clinical team for advice. It’s all about finding the perfect dose that balances the benefits of treatment while keeping the side effects at bay - we can help guide you to find this sweet spot."
Mounjaro and low blood pressure
Your blood pressure might dip while you’re using Mounjaro. There’s a few possible reasons why: it could be due to the weight you’ve lost or because your blood sugar has dropped too low, for instance.
While dizziness typically goes away on its own, there are some things you can do to help:
- Drink plenty of fluids, especially water. Dehydration can contribute to dizziness
- If you can, lie down until you feel better
- Move around as slowly and carefully as possible
- Avoid coffee and alcohol as they can make you dehydrated
- Rest!
Less common or more serious side effects of Mounjaro
There are also a few more serious side effects to be aware of, including:
- Gallbladder disorders
- Very low blood sugar
- Pancreatitis
- Kidney disease
- Thyroid cancer
- Allergic reactions
- Diabetic retinopathy
While these problems are unlikely to happen, it’s really important that you can pick up on any issues that might warrant medical attention. Let’s run through them one by one:
Gallbladder disorders
If you have any pre-existing gallbladder problems, Mounjaro probably won’t be prescribed to you, as you’re at an increased risk of experiencing these from treatment. In clinical trials, 0.6% of patients developed an acute gallbladder disorder (such as inflammation of the gallbladder or gallstones).
Warning signs include high fever, yellowing of the skin, or sudden pain in the right upper abdomen or between the shoulder blades. Stop treatment and seek immediate medical attention if you experience these symptoms.
Very low blood sugar (hypoglycemia)
As well as making you feel full, did you know that Mounjaro keeps your blood sugar levels under control? In some people, these levels can drop too low and cause hypoglycemia.
Warning signs include dizziness, anxiety, sweating, shaking, and confusion. In clinical trials, mild hypoglycemia on Mounjaro was relatively common, but severe hypoglycemia was very rare.
This can happen if you’re taking another medication as well as Mounjaro that lowers your blood sugar, like the diabetes drugs insulin or sulfonylureas. The effects of these medicines can overlap with Mounjaro’s and bring your blood sugar below normal levels.
Per clinical research, 9% of people with type 2 diabetes taking sulfonylureas as well as Mounjaro experienced hypoglycemia, compared to 1-3% of Mounjaro users who were not on sulfonylureas.
Pancreatitis
Very rarely Mounjaro users can develop acute pancreatitis, a condition in which the pancreas becomes inflamed. The symptoms include severe pain in your abdomen and a high fever. It can sometimes become a chronic problem. If you experience these symptoms, seek medical attention immediately. If you have a previous history of pancreatitis, you should not take Mounjaro.
Kidney problems
A few patients taking Mounjaro have developed acute kidney injury, mostly after severe episodes of vomiting and diarrhoea. During times of diarrhoea or vomiting, it’s important to keep your fluid levels up so you don’t become dehydrated. If you experience these symptoms, please seek medical help urgently. If you have kidney impairment, you might not be able to take Mounjaro (depending on how severe it is). Speak to your clinical team to check your suitability for treatment.
Thyroid cancer
Mounjaro isn’t suitable for people with a personal or family history of medullary thyroid cancer. In studies on rats, Mounjaro and other weight loss drugs have been linked to thyroid tumours. We don’t know whether the same applies to humans, but if you experience any warning sign (think a lump in your neck, shortness of breath or trouble swallowing), don’t ignore them and seek medical help immediately.
Allergic reactions
Allergic reactions to Mounjaro are rare. But if you experience swelling of the face, rapid heartbeat, severe rash, or problems breathing, make sure to get medical help immediately. If you experience a mild skin reaction at the injection site, this is also something to mention to your doctor.
Long-term side effects of Mounjaro
Most of the time, your side effects will ease off as you adjust to the medication, or stop if you discontinue treatment. But if you are unlucky enough to experience a serious side effect, like pancreatitis or kidney damage, it might take a while before you’re better.
It’s worth noting that Mounjaro has only been on the market since 2022, with the first clinical trials taking place in 2018. That means we don’t yet have a huge trove of long-term data.
What if a side effect I’m experiencing is not listed
We’re still learning about all the different ways that Mounjaro affects the body. If you experience anything that’s bothering you which isn’t listed as a side effect, don’t panic—check in with your doctor for advice.
You can also report your side effects directly to the MHRA via the yellow card scheme. This is a government-run organisation that monitors medication for any emerging or new side effects, to ensure the safety of treatment: https://yellowcard.mhra.gov.uk/
Side effects support at Voy
As part of our weight loss programme, you’ll get one-to-one guidance and support from our team of clinicians and coaches. That includes advice on how to manage your side effects and get any treatment that you need.
Advice from Phoebe Fox - Weight Loss Specialist Clinician: "At Voy, we’re just a phone call away. If you’re experiencing side effects, we can offer advice, prescribe treatment to manage the symptoms, and adjust your dose to find the right balance. We’re always here to work with you, to make sure you get the best out of your weight loss journey."
How to manage the side effects of Mounjaro?
The good news is that Mounjaro side effects are usually mild—and can be easily managed at home. But if your side effects are more serious or don’t go away (for instance, if you have severe stomach pain or think you’re having an allergic reaction), check in with your provider right away.
Here’s some tips for dealing with mild symptoms.
For nausea:
- Eat smaller, more frequent meals
- Drink ginger or peppermint tea
- Get some fresh air
- Eat more slowly
- Steer clear of fried, greasy or strong-smelling food
- Avoid alcohol and caffeine, especially as you start treatment
- Make sure to drink lots of fluids
- Get plenty of rest
- Eat bland foods and foods low in fibre (such as dry toast) when you feel up to it
- Avoid foods and drinks that aggravate the problem (think coffee, alcohol, or full-fat dairy)
For constipation:
- Drink plenty of water
- Eat foods high in fibre (such as wheat bran and oats)
- Eat fruits containing sorbitol (apples, apricots grapes, raisins, raspberries, and strawberries)
- Get out for a brisk walk or run
For tiredness:
- Eat little and often
- Review your calorie consumption to ensure you’re eating enough
- Gradually cut down on caffeine to improve sleep, especially in the afternoon and evening
- Cut down on alcohol
- Stay well hydrated
- Do things that reduce your stress levels
- Try some gentle exercise but steer clear of extreme exercise
- Take some time to relax and wind down before bed.
- Choose a different spot for the injection each time. You can use the same area of your body (i.e. stomach, thighs, upper arms), but inject the pen into a different spot. This reduces your chance of irritation
- Apply a cold compress
- Take an antihistamine
- Take your injection out of the fridge for around 30 minutes before injecting to allow it to reach room temperature
Over-the-counter remedies may be able to help ease some of these symptoms, too. For example, Pepto-Bismol can sometimes be used for nausea or diarrhoea. Ask your provider if you’re not sure, or just pop down to your local pharmacy.
In some cases, your provider may suggest prescription medicine. They’ll advise on what’s best for you, so be sure to follow their instructions exactly.
When do Mounjaro side effects start?
If you do experience side effects, they’ll probably start soon after your first injection or when you increase the dose. According to a 2023 review of the evidence, gastrointestinal symptoms tend to appear within two weeks of beginning Mounjaro, but they are typically mild and short-lived. You may also experience side effects any time you up your dose.
But if your symptoms hang around or get worse, your provider may suggest dropping back down to a lower dose. This is because it can take time for your body to adjust to higher strengths of the medicine, and going down to a lower dose might help you adapt more gradually. Once your symptoms are under control, your provider may try to move you up again. FYI: It’s absolutely fine to be on a lower dose of Mounjaro. It will still work!
Some of the more serious side effects may appear at a later stage. For instance, kidney problems tend to arise after an episode of being very sick and dehydrated. Symptoms of gallbladder disease may come on suddenly. Allergic reactions, on the other hand, will appear very soon after you take the medicine.
How long do Mounjaro side effects last?
You’re most likely to experience side effects when you first start taking Mounjaro or increase your dose. It’s common to feel a bit queasy during the first few days, and again each time your dose goes up. However, your body typically adjusts over time, and the side effects often ease with continued use.
Usually, mild symptoms will go away within a few days or weeks. Though more serious side effects may require treatment and can take a bit longer to clear.
What should I do if my side effects don't go away after a few weeks?
If side effects continue beyond several weeks or significantly impact your quality of life, these steps could help:
- Contact your healthcare provider to discuss your symptoms.
- Keep a symptom diary to track when side effects occur and their severity.
- Consider whether specific foods or activities trigger or worsen your symptoms.
- Discuss dose adjustment options with your provider.
- Consider stopping the treatment or pausing your next dose until you’ve spoken with your prescriber.
Remember, your healthcare provider can help you safely adjust your treatment plan if needed.
Once you stop taking Mounjaro, it will be entirely cleared from your body in about 30 days. Half the medication will leave your system within five days, which should help relieve any negative symptoms.
Does everyone get side effects from Mounjaro?
Unfortunately, it’s impossible to say beforehand how your body will respond to Mounjaro. Some people experience no side effects, while others develop mild ones. And a far smaller proportion deal with something more severe. Everyone’s different, and your friend’s experience of Mounjaro may not reflect your own.
That’s why doctors will always start you on a low dose—to prevent side effects and allow your body to slowly adjust to the medication. The dose may be increased by 2.5mg every month depending on your individual needs and preferences.
However, certain medications might compound the effects of Mounjaro and make you more likely to get symptoms. We mentioned one example earlier; if you use diabetes medication that lowers your blood sugar while on Mounjaro, there’s a risk it will dip too low.
The effects of drinking alcohol can also overlap with Mounjaro symptoms and make you feel worse. For instance, both can make you nauseous or want to be sick. We’d suggest avoiding alcohol while you’re using Mounjaro.
Plus, foods that are acidic, spicy, or high in fat can upset your stomach and make gut-related symptoms more intense.
And to reiterate: If your symptoms don’t go away, are affecting your day-to-day life, or are getting worse, see your doctor asap. As well as helping you get any treatment you need, they might suggest switching up your dose or even trying a different weight loss medicine.
Are there any side effects of missed Mounjaro doses?
Did you miss a dose of Mounjaro? Don’t worry—it happens. It won’t disrupt your progress. If you’re still within four days of the missed dose, take it as soon as you can. However, you shouldn’t take two doses of Mounjaro within three days of each other. If more than four days have gone by since the missed dose, skip this one and take the next dose on your usual day.
But will a missed dose of Mounjaro cause side effects? After about a week, the effects of Mounjaro will start to dwindle. So you might notice that your appetite starts to come back, for instance. Mounjaro isn’t known to cause any sort of withdrawal symptoms, though.
Check in with your provider if you miss a few doses in a row. They might suggest that you re-start on a lower dosage, so your body can re-adjust to the medicine. There’s a chance you’ll experience side effects again when resuming Mounjaro.
Your weight loss journey
Thinking about Mounjaro’s side effects can be daunting. However, it needn’t be the end of the road for your weight loss goals! Although side effects are common, most of the time they’re short-lived and unlikely to disrupt your life.
All this said, you should never feel that you have to suffer in silence. It’s really important to work with your doctor throughout your Mounjaro journey. They will help you find a dose that’s right for you—one that delivers the best possible outcomes while keeping side effects to a minimum. And remember, always call your doctor if you do experience anything concerning.
If you just want someone to talk to, Voy includes an app to track your progress, which gives you access to our clinical team. Through the Voy app, you can easily contact your coach for personalised support, advice and understanding. You can also call our support line to speak with a clinician within minutes if you have any concerns or want to discuss your treatment in more detail.
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