If you are having chest pain right now, call 999. Chest pain that does not go away, feels like squeezing or pressure, spreads to your arm, neck, jaw or back, or comes with breathlessness, sweating, nausea or feeling faint needs urgent assessment. Do not try to work out whether Mounjaro is the cause before getting medical help.
Chest pain is not listed as an adverse reaction in the current UK Mounjaro product information. However, that does not mean new chest pain should be ignored or automatically blamed on something else. Chest pain can have many causes, including heart problems, reflux and indigestion, so new or unexplained chest pain needs appropriate medical assessment.
For everything else, this guide looks at what we actually know about Mounjaro and the heart, including its effect on heart rate and the latest cardiovascular trial data.
Key things to know
- Increased heart rate is a listed common adverse reaction with Mounjaro for adults with type 2 diabetes. Common means it can affect between 1 in 100 and fewer than 1 in 10 people. In weight management studies, increased heart rate was less frequent and classed as uncommon.
- In adult type 2 diabetes studies, the maximum mean increase in heart rate was 3 to 5 beats per minute across doses. In weight management studies, the mean increase was about 3 beats per minute. In SURPASS CVOT, the maximum mean increase was 6 beats per minute.
- Chest pain and heart attack are not listed as adverse reactions in the current UK Mounjaro product information. Palpitations are also not separately listed. A noticeable racing heartbeat can, however, be related to an increase in heart rate or to other factors such as dehydration or low blood sugar.
- SURPASS CVOT included 13,299 adults with type 2 diabetes and established cardiovascular disease. After a median follow up of 4 years, tirzepatide was not worse than dulaglutide for the main combined outcome of cardiovascular death, heart attack or stroke.
- Having an existing heart condition does not automatically mean that Mounjaro cannot be prescribed. Your prescriber needs to know about your heart condition and all the medicines you take so they can decide whether treatment is appropriate for you.
Chest Pain: What to Do
Chest pain deserves a direct answer because it is not something you should simply put down to Mounjaro.
Chest pain is not listed as an adverse reaction to Mounjaro. However, the absence of chest pain from the side effect list does not tell you what is causing your symptoms. Chest pain can come from the heart, lungs, digestive system, muscles or other causes.
Call 999 if you have sudden chest pain that does not go away, particularly if it feels tight, heavy, squeezing or like pressure. You should also call 999 if the pain spreads to your arm, neck, jaw or back, or if you have chest pain with sweating, nausea, light headedness or shortness of breath.
Mounjaro can cause gastro oesophageal reflux disease, which may feel like burning or discomfort in the chest. It is often worse after eating or when lying down. Even so, you should not try to diagnose new chest pain as reflux yourself, particularly if the pain is severe, unusual or does not settle.
If your chest pain comes and goes or goes away quickly but you are still worried, speak to your GP or seek advice from NHS 111.
Does Mounjaro Increase Your Heart Rate?
Yes. Mounjaro can increase heart rate, and this is included in the current UK prescribing information.
For adults with type 2 diabetes, increased heart rate is classed as a common adverse reaction. In pooled clinical studies, the maximum mean increase was 3 to 5 beats per minute across the different doses. In weight management studies, the mean increase was around 3 beats per minute.
That is an average change, so your own heart rate may change by more, less or not at all. A small change on its own does not necessarily mean that there is a problem with your heart.
By how much?
The current data give a clearer picture than simply saying that Mounjaro causes a small increase.
In type 2 diabetes studies, the maximum mean increase was 3 to 5 beats per minute. In SURPASS CVOT, which included people with type 2 diabetes and established cardiovascular disease, the maximum mean increase was 6 beats per minute. In weight management studies, the mean increase was about 3 beats per minute.
Individual results can be different from these averages. You may notice no change, while another person may notice their heartbeat more clearly.
It is also worth remembering that heart rate changes throughout the day. Exercise, stress, caffeine, dehydration, illness and even standing up can temporarily make your heart beat faster.
Why does it happen?
The exact reason Mounjaro increases heart rate is not completely understood. The effect has been seen in clinical studies, so it is better to acknowledge it than to give a definite explanation that has not been established.
There are also other reasons why your heart rate might increase while taking Mounjaro:
- Dehydration. Nausea, vomiting and diarrhoea can cause you to lose fluids. They can also contribute to electrolyte disturbances. This can make you feel weak, dizzy or aware of your heartbeat.
- Low blood pressure. Hypotension and related events are listed with Mounjaro. A drop in blood pressure can sometimes be accompanied by a faster heart rate.
- Low blood sugar. The risk of hypoglycaemia is higher when Mounjaro is used with insulin or a sulphonylurea. A fast heartbeat can be one of the symptoms of low blood sugar.
- Anxiety or stress. Feeling worried about your heart can itself make your heart beat faster. This can create a frustrating cycle where you notice your heartbeat, become more worried and then notice it even more.
If you take a beta blocker, it is worth telling your prescriber. Beta blockers can affect heart rate and may also change how some symptoms of low blood sugar are noticed.
Is a raised heart rate dangerous?
A small increase in heart rate is an expected effect of Mounjaro in some people. The clinical trial data do not show that these small average increases are accompanied by an increase in arrhythmia or cardiac conduction problems compared with placebo in the type 2 diabetes studies.
However, that does not mean every change in heart rate should be ignored.
Speak to a GP or your prescriber if your resting heart rate stays unusually high, keeps increasing, or you regularly feel your heart racing or pounding.
Seek urgent medical help if a fast or irregular heartbeat happens with chest pain, severe breathlessness, fainting or feeling very unwell.
If you already have an arrhythmia or take medicines that affect your heart rate, tell your prescriber before starting Mounjaro or if these symptoms develop.
What about a low heart rate?
A slowed heart rate is not listed as an adverse reaction to Mounjaro in the current UK product information.
If your heart rate has become noticeably lower, there could be another explanation, such as a rate controlling medicine, changes in fitness or another health condition.
If a low heart rate is accompanied by dizziness, fainting, unusual weakness, chest pain or severe breathlessness, seek medical advice promptly.
Is Mounjaro Safe If You Have a Heart Condition?
Having a heart condition does not automatically mean that you cannot take Mounjaro. The current UK product information lists hypersensitivity to tirzepatide or one of its ingredients as the contraindication. Other health conditions need to be considered as part of an individual prescribing decision.
This is particularly important if you have had a heart attack, stroke, heart failure, an arrhythmia, a stent or bypass surgery. Your prescriber should know about your medical history and any medicines you take before deciding whether Mounjaro is suitable.
What the large cardiovascular trial found
SURPASS CVOT was a large cardiovascular outcomes trial involving 13,299 adults with type 2 diabetes and established cardiovascular disease. Participants were treated with tirzepatide or dulaglutide and were followed for a median of 4 years.
The main outcome combined cardiovascular death, heart attack and stroke. It occurred in 12.2% of people taking tirzepatide and 13.1% of those taking dulaglutide. The result met the study's criteria for non inferiority. In simple terms, tirzepatide was not shown to be worse than dulaglutide for this main cardiovascular outcome.
A later analysis of the same trial also reported all cause mortality in 8.6% of people in the tirzepatide group and 10.2% in the dulaglutide group. However, this was a secondary analysis and should not be interpreted as meaning that Mounjaro is prescribed to prevent death or heart disease.
Gastrointestinal adverse events were reported in 42.5% of people taking tirzepatide compared with 35.9% taking dulaglutide in the later analysis.
Two important points to keep in mind
First, SURPASS CVOT compared tirzepatide with dulaglutide. It was not a trial comparing tirzepatide with no treatment. The main result showed that tirzepatide was non inferior to dulaglutide for cardiovascular death, heart attack and stroke. That is different from saying that Mounjaro is a heart treatment.
Second, Mounjaro is licensed in the UK for type 2 diabetes and for weight management in eligible adults. It is not prescribed simply as a medicine to prevent heart attacks.
Mounjaro can affect several factors linked with cardiovascular health, including body weight and blood pressure. However, those effects should not be turned into a promise that taking Mounjaro will prevent heart disease or a future heart attack.
Heart Failure, Palpitations and Heart Attack
Heart failure
Heart failure is not listed as an adverse reaction to Mounjaro in the current UK product information. The SURPASS CVOT trial also included people who already had heart failure at the start of the study.
If you have heart failure, Mounjaro still needs to be considered as part of your overall treatment. This is especially important if you take diuretics or other medicines that affect fluid balance because vomiting or diarrhoea can cause dehydration. Mounjaro's product information specifically warns about fluid loss from gastrointestinal side effects.
Tell your prescriber if you have heart failure and let them know about all your heart medicines.
Palpitations
Palpitations are not separately listed as an adverse reaction to Mounjaro. However, some people may notice their heartbeat more clearly when their heart rate increases. Other factors, such as dehydration, low blood sugar, anxiety or medicines, can also cause a racing or pounding heartbeat.
If palpitations keep happening, are new for you or are becoming more frequent, speak to your GP or prescriber.
Get urgent help if palpitations happen with chest pain, severe breathlessness, fainting or feeling very unwell.
Can Mounjaro cause a heart attack?
Heart attack is not listed as an adverse reaction to Mounjaro in the current UK product information. The SURPASS CVOT trial also found that tirzepatide was non inferior to dulaglutide for its combined outcome of cardiovascular death, heart attack and stroke in people with type 2 diabetes and established cardiovascular disease.
That does not mean a heart attack cannot happen while someone is taking Mounjaro. People taking Mounjaro can still develop heart disease or have a heart attack for other reasons.
If you have symptoms that could indicate a heart attack, treat them as an emergency rather than assuming they are related to Mounjaro.
If You Take Cardiac Medicines
There are a few practical things to consider if you take heart or blood pressure medicines alongside Mounjaro.
Mounjaro slows stomach emptying. This can change how quickly some oral medicines are absorbed, particularly when treatment is started or the dose is increased. The current product information says that most oral medicines are not expected to need a dose adjustment, but extra monitoring is recommended for medicines with a narrow therapeutic range, such as warfarin or digoxin.
Vomiting and diarrhoea can also cause fluid and electrolyte loss. This may matter more if you take diuretics or medicines for blood pressure. Tell your prescriber if you have ongoing vomiting or diarrhoea rather than simply trying to manage it yourself.
Mounjaro can also lower blood pressure and body weight in some people. If your blood pressure changes or you start feeling dizzy or light headed, your prescriber may need to review your existing medicines. Do not reduce or stop a heart or blood pressure medicine yourself.
Tell your prescriber about:
- any previous heart attack or stroke
- heart failure
- an irregular heart rhythm or other arrhythmia
- a stent, bypass or other heart procedure
- a pacemaker or implanted heart device
- all heart and blood pressure medicines
- any other regular medicines
You should also mention if you have kidney disease, particularly if you are experiencing vomiting or diarrhoea, because dehydration can affect kidney function.
There is no requirement for every person taking Mounjaro to have routine ECGs or regular heart rate checks simply because they are taking the medicine. Any monitoring you need depends on your health and should be arranged with your GP, prescriber or cardiologist.
When to Seek Medical Advice
Call 999 if you have sudden or persistent chest pain, particularly if it feels tight, heavy, squeezing or like pressure, or if it spreads to your arm, neck, jaw or back. Call 999 if chest pain comes with severe breathlessness, sweating, nausea, light headedness or fainting.
Get urgent medical help if you have severe difficulty breathing, especially if you are struggling to speak normally because of breathlessness, or if you have signs of a severe allergic reaction such as swelling of the face, lips, mouth or throat or difficulty breathing. Severe allergic reactions, including anaphylaxis, have been reported rarely with tirzepatide.
Contact your GP or prescriber if you have repeated palpitations, a persistently raised resting heart rate, unusual breathlessness, dizziness, ankle swelling or ongoing vomiting or diarrhoea.
You should also seek medical advice for persistent or severe abdominal pain. Acute pancreatitis has been reported with tirzepatide. The current UK product information advises patients to seek immediate medical attention for persistent, severe abdominal pain, particularly when pancreatitis is suspected.
Medical Disclaimer
This article is for general information only and does not replace individual medical advice.
If you have an existing heart condition, your prescriber should consider your medical history, current medicines and other health conditions before deciding whether Mounjaro is appropriate for you.
Mounjaro can cause gastrointestinal side effects such as nausea, vomiting and diarrhoea. These can lead to dehydration and electrolyte disturbances, which may be more important if you have heart or kidney problems or take medicines that affect fluid balance.
Mounjaro is also associated with gallbladder problems such as gallstones and cholecystitis. In weight management studies, acute gallbladder events were positively correlated with weight reduction. This does not mean that everyone taking Mounjaro will develop a gallbladder problem, but persistent or severe abdominal symptoms should be discussed with a healthcare professional.
Do not stop or change your heart, blood pressure or diabetes medicines without medical advice. If you take Mounjaro for type 2 diabetes, your treatment may need to be reviewed if your blood glucose, weight, food intake or other health conditions change.
If you have chest pain, severe breathlessness or fainting, call 999.