What is atrial fibrillation?
AF is an irregular and often fast heart rhythm. It happens when the upper chambers of the heart, the atria, fire chaotic electrical signals instead of beating in a steady rhythm.3
Some people feel obvious symptoms. Palpitations, breathlessness, chest tightness, dizziness, and fatigue are all common.
Others don’t notice anything, and AF is picked up incidentally during a routine check-up or as part of investigations for something else.3
The clinical concern with AF isn’t the rhythm itself. It’s the increased risk of stroke, which is roughly five times higher than for people without AF, and the increased risk of heart failure if AF is poorly controlled over time.2
Most people with AF in the UK are managed using what’s known as the ABC pathway: Anticoagulation to lower stroke risk, Better symptom control through rate or rhythm-control medication, and Comorbidity and lifestyle management, which includes weight, blood pressure, sleep, and alcohol.2
Weight management sits firmly in the C of that pathway, and it’s where Mounjaro becomes relevant.
How Mounjaro works
Mounjaro is a once-a-week injection that contains the drug tirzepatide. It mimics two gut hormones, GLP-1 and GIP, which communicate with the brain’s appetite centre to reduce hunger and food-seeking behaviour.4
It also slows down digestion, so food stays in the stomach longer. You feel full sooner during a meal and stay satisfied for longer afterwards.
In the SURMOUNT-1 trial, people taking the highest dose of Mounjaro lost an average of 20.9% of their body weight over 72 weeks, compared with 3.1% on placebo.4
In SURMOUNT-4, continued tirzepatide treatment over 88 weeks led to a mean total weight loss of approximately 25%.5
For someone with AF, the relevance isn’t a direct effect on heart rhythm. It’s that meaningful, sustained weight loss is one of the few interventions with strong evidence for reducing AF burden over time
.1
Weight and atrial fibrillation
The link between body weight and AF is one of the more clearly established relationships in cardiology.
Higher body weight increases the risk of AF developing, makes existing AF harder to control, and increases the risk of AF returning after ablation.1
Excess body fat raises blood pressure and inflammatory markers, contributes to obstructive sleep apnoea, and, over time, enlarges the left atrium. The bigger the atrium gets, the more likely AF episodes become..2
LEGACY showed what happens when this is reversed. Among people with AF who lost 10% or more of their body weight, 45.5% were free of AF symptoms at five years without rhythm-control medication or ablation. In people who lost less than 3%, that figure was 13.4%.1
Weight loss in LEGACY also reduced left atrial size, blood pressure, and the burden of AF episodes on monitoring.
Mounjaro, on its own, doesn’t deliver the structured support that LEGACY tested, but it does make sustained weight loss easier for many people to achieve.
Sleep apnoea and AF often go together
Obstructive sleep apnoea, where breathing repeatedly pauses during sleep, is one of the strongest reversible triggers for AF.
It’s also heavily underdiagnosed, particularly in people who don’t sleep with a partner who notices it.2
Untreated sleep apnoea is one of the leading reasons for AF returning after ablation. Weight loss reduces apnoea severity in most people, and even modest weight loss can make a measurable difference.
If you snore heavily, wake unrefreshed, or feel sleepy during the day, it’s worth asking your GP about a sleep study.
Treating sleep apnoea alongside weight loss tends to yield better AF outcomes than either approach alone.
Mounjaro and heart rate
Tirzepatide modestly increases resting heart rate. A 2024 systematic review found that, on average, tirzepatide raised resting heart rate by around 1.8 beats per minute compared with placebo, with a slightly larger effect at the 15 mg dose.6
This effect is similar to what’s seen with other GLP-1 medications, like Wegovy (semaglutide).
Why these medications increase heart rate isn’t fully understood, but it’s thought to involve modest changes in the part of the nervous system that regulates heart rate, rather than any direct electrical effect on the heart.6
In the SURMOUNT trial programme, this small increase in heart rate didn’t translate into more major adverse cardiac events. SURMOUNT-1 and SURMOUNT-4 both reported overall cardiovascular safety in line with placebo.4,5
It’s still worth flagging with your cardiologist. For well-rate-controlled AF on a beta-blocker, a few extra beats per minute rarely affect how you feel.
For symptomatic, fast AF, your cardiologist may want to review rate-control medication after a few weeks on Mounjaro.
Tirzepatide isn’t contraindicated in AF. The 2024 European Society of Cardiology AF guidelines and NICE NG196 both treat weight management as a positive lifestyle intervention.2,7
What to look out for in the first few weeks
Most people on Mounjaro don’t notice any heart-related issues, particularly if their AF is well rate-controlled.
The early weeks and the period after each dose increase are when any heart rate effect is most likely to show up. Here are a few symptoms worth flagging to your GP, AF nurse, or cardiologist:
- New or worsening palpitations, especially if episodes feel longer or more frequent than usual
- A faster-than-usual resting heart rate, if you check it
- Light-headedness or dizziness, especially when standing up
- Increased breathlessness on exertion compared with your baseline
- An AF episode that’s harder to break than usual or doesn’t respond to your usual rescue plan
None of these is an emergency on its own, unless symptoms are severe. They’re conversations worth having with your AF team, not reasons to stop Mounjaro.
Anticoagulation considerations
Most people with AF in the UK are on an anticoagulant to reduce stroke risk, usually a direct oral anticoagulant (DOAC) such as apixaban, rivaroxaban, edoxaban, or dabigatran. Some are still on warfarin.2
There’s no direct chemical interaction between tirzepatide and any of these. The points to be aware of are indirect, and they centre on weight loss and reduced food intake.
Apixaban dosing depends partly on body weight. The lower 2.5 mg twice-a-day dose applies when two of the three criteria are present: age 80 or older, weight 60 kg or less, or reduced kidney function.
If your weight exceeds 60 kg, your prescriber may want to review the dose.
Rivaroxaban needs to be taken with food at the doses used in AF. Mounjaro reduces appetite, so it’s best to take rivaroxaban with a proper meal rather than a small snack.
Warfarin is the most sensitive to dietary change. Reduced vegetable intake can lower vitamin K levels and raise your INR.
Your anticoagulation service will usually want to check INR more often during the first few months on Mounjaro.
For a fuller breakdown of how Mounjaro affects each anticoagulant, see our guide on Mounjaro and anticoagulants.
For specific guidance on rate- and rhythm-control drugs such as beta-blockers, calcium channel blockers, amiodarone, and flecainide, see our guide on Mounjaro and heart rhythm medications.
If you’re taking other medications alongside Mounjaro, our GLP-1 medication compatibility checker covers the most common combinations.
Foods to focus on with atrial fibrillation
There’s no specific ‘AF diet’. The strongest dietary evidence in AF supports a Mediterranean-style pattern, both for general cardiovascular outcomes and as part of the structured weight management approach used in trials like LEGACY.1,2
Build meals around vegetables, lean meat, lean and oily fish, beans and lentils, olive oil, nuts and seeds, and fibre-rich complex carbohydrates. Limit ultra-processed foods, refined grains, and added sugars.
The balanced plate model (half vegetables, a quarter protein, a quarter complex carbohydrates, plus a serving of fat) is a useful framework when your appetite is lower than usual on Mounjaro.
There are three areas that need extra attention if you have AF: alcohol, potassium, and caffeine.
Alcohol
Alcohol is one of the most consistent AF triggers. Even moderate drinking can provoke episodes in some people, and binge drinking is well-recognised enough as a trigger to have its own term, ‘holiday heart’.2
UK guidelines suggest staying under 14 units a week, spread across several days with alcohol-free days in between.
For people with symptomatic AF, your cardiologist may suggest cutting back further or stopping altogether to see whether episodes become less frequent.
Tirzepatide can also reduce tolerance to alcohol because of its effects on the gut. Many people find they want to drink less anyway.
Potassium-rich foods
Adequate potassium supports normal heart electrical activity. Most people get enough from a balanced diet, but reduced food intake on Mounjaro can lower overall intake.
Potatoes (with skin), beetroot, spinach, beans, bananas and yoghurt are good sources to include. If you’re on a potassium-sparing diuretic or an ACE inhibitor, don’t add supplements without your prescriber’s input.
Caffeine and stimulants
Moderate caffeine isn’t a clear AF trigger for most people. Pre-workout supplements, energy drinks, and high-dose caffeine pills are a different category, and worth avoiding if you have AF, especially if your AF is symptomatic.
Movement with atrial fibrillation
Regular physical activity is part of standard AF management. Observational studies suggest that moderate-intensity exercise reduces AF burden and improves quality of life, alongside the broader cardiovascular benefits.1,7
Building a small, regular habit works better than aiming for a weekly target you might miss.
Research on habit formation suggests it takes an average of 66 days for a new behaviour to become automatic.8
The most reliable approach is to start small and link the habit to something you already do, like a 10-minute walk after dinner.
Once that small habit feels natural, you can gradually do a little more as it feels manageable.
Aerobic activity
Walking, cycling, swimming, and gentle jogging are all good options. Moderate intensity is generally well-tolerated in AF and is the level most consistently linked to lower AF burden in observational studies.1
If you use a heart rate monitor, readings can be erratic during AF episodes. Perceived effort is a more useful guide; aim for the level where you can talk in short sentences between breaths.
Resistance training
Resistance training, using bodyweight, resistance bands, free weights, or machines, helps preserve muscle during weight loss.
Mounjaro doesn’t selectively reduce fat, so without active resistance work, some of the weight lost can come from muscle.
Two sessions a week covering the main muscle groups is a reasonable target to build towards. Start with shorter sessions and lighter loads, and progress gradually.
A note on high-intensity exercise
Very high-intensity training, such as HIIT or competitive endurance work, can occasionally trigger AF episodes in people who are already symptomatic. This doesn’t mean intense exercise is off the table forever, but if you have symptomatic AF, it’s worth discussing with your cardiologist before stepping up to that level.
The NHS recommends 150 minutes of moderate activity per week for general health. That’s a useful taget to aim for, not where you need to start.
Aim for whatever feels manageable today, then add a few minutes each week as your symptoms allow.
Looking after your mental health
Anxiety is common in AF, and it often goes unrecognised.
A 2024 meta-analysis of studies covering people with AF found pooled prevalence estimates of around 14.5% for anxiety and 24.3% for depression.
Among older adults with AF, the figures were higher, at 33.6% for anxiety and 40.3% for depression.9
These rates are well above the general population and tend to cluster among those most affected by symptoms.
The AF-anxiety cycle
AF involves an unpredictable, irregular heartbeat that you can sometimes feel. Many people with symptomatic AF describe a heightened awareness of their heartbeat, which can become self-reinforcing.
Noticing palpitations leads to anxiety, which raises sympathetic activity, which can, in turn, make episodes more noticeable or more frequent.
The fear of stroke sits underneath all of this. AF is one of the few conditions where most people are told, explicitly, that they’re at higher stroke risk and that anticoagulation is what’s holding that risk down. That’s an accurate framing, but it can be hard to live with.
Talking therapy and practical steps
Cognitive behavioural therapy (CBT) has reasonable evidence for helping people manage AF-related anxiety.
Your GP can refer you, and in England, you can usually self-refer to NHS Talking Therapies (formerly IAPT).
Searching ‘NHS Talking Therapies near me’ will bring up your local service.
Practical steps that often help include tracking episodes, agreeing on a clear plan with your cardiologist for what to do during an episode, limiting caffeine and alcohol, and prioritising sleep.
Sleep apnoea is both an AF trigger and a driver of low mood, so it’s worth raising with your GP if you suspect it.
If low mood, anxiety, or thoughts of self-harm last for more than a couple of weeks, speak to your GP.
Mention if anything has changed recently with your AF, your medication, or your sleep, since these can all feed into mood.
Mounjaro clinical data
The table below summarises Mounjaro alongside the other GLP-1 medications most often used for weight management in the UK.
It’s general data, not AF-specific, since none of these has been studied in AF cohorts directly.
| Measure |
Mounjaro (tirzepatide) |
Wegovy (semaglutide) |
Saxenda / Nevolat (liraglutide) |
| Mechanism |
Dual GLP-1 and GIP receptor agonist |
GLP-1 receptor agonist |
GLP-1 receptor agonist |
| Administration |
Once a week, subcutaneous injection |
Once a week, subcutaneous injection |
Once a day, subcutaneous injection |
| Average weight loss |
Up to 20.9% at 72 weeks (SURMOUNT-1, 15 mg)4 |
Around 14.9% at 68 weeks (STEP 1) |
Around 8% at 56 weeks (SCALE) |
| Effect on heart rate |
Modest rise of around 1.8 bpm vs placebo6 |
Modest rise (similar GLP-1 class effect) |
Modest rise (similar GLP-1 class effect) |
| Direct interaction with AF medications |
None reported |
None reported |
None reported |
| Cardiovascular safety in trials |
No increase in major adverse cardiac events in SURMOUNT-1 to SURMOUNT-44,5 |
Reduces cardiovascular events in people with established CVD (SELECT) |
Neutral to slightly favourable in people with type 2 diabetes (LEADER) |
| UK availability |
Available privately and through NHS for selected patients |
Available privately and through NHS for selected patients |
Branded Saxenda discontinued; generic liraglutide (Nevolat) available privately |
Frequently asked questions
Does Mounjaro cause atrial fibrillation?
There’s no evidence that Mounjaro causes AF. Tirzepatide raises resting heart rate by around 1.8 beats per minute on average, but the SURMOUNT trial programme didn’t show an increase in arrhythmias or major adverse cardiac events compared to placebo.4,5,6
Will Mounjaro make my AF episodes more frequent?
This isn’t expected. The opposite is more likely over time, since meaningful weight loss reduces AF burden in trials like LEGACY.1
If you do notice more episodes after starting Mounjaro, it’s worth discussing with your cardiologist rather than stopping the medication on your own.
Can I take Mounjaro if I’m on apixaban or rivaroxaban?
Yes, with appropriate monitoring. There’s no direct interaction between tirzepatide and DOACs.
The points to watch are weight crossing the 60 kg threshold for apixaban dosing, and taking rivaroxaban with a proper meal, even when your appetite is lower. Our anticoagulants guide covers this in detail.
What about beta-blockers, amiodarone, or flecainide?
None of these has a direct interaction with tirzepatide. As you lose weight, the dose of rate-control medication you need may change, especially for beta-blockers and calcium channel blockers. Our heart rhythm medications guide covers each drug class in more detail.
Should I tell my cardiologist if I’m starting Mounjaro?
Yes. Your cardiologist needs to know about any new medication, and Mounjaro is one that can affect your AF management plan over time. They may also want to repeat blood pressure, heart rate, and ECG checks as you progress.
Is it safe to exercise on Mounjaro if I have AF?
For most people, yes, and exercise is part of standard AF management. Moderate intensity is generally well-tolerated.
Very high-intensity training can occasionally trigger episodes in symptomatic AF, so build up gradually and discuss with your cardiologist if you’re aiming for that level.
How quickly might my AF improve on Mounjaro?
The largest reductions in AF burden tend to occur once weight loss reaches around 10%, based on LEGACY data.1
On Mounjaro, that level of weight loss usually takes several months.
Earlier wins often show up sooner. Blood pressure, sleep, breathlessness, and exercise tolerance can improve at 5% weight loss or less.
If you have obstructive sleep apnoea, even modest weight loss can reduce its severity, which can in turn reduce your AF burden.
Can I take Mounjaro if I’m planning a pregnancy?
Mounjaro isn’t recommended in pregnancy. If you’re planning to conceive, your prescriber will usually advise stopping it ahead of trying.
AF medications often need review in pregnancy too: some anticoagulants and anti-arrhythmics aren’t safe in early pregnancy, and others need dose changes. Talk to your cardiologist and GP early so any medication changes can be coordinated safely.
Is Mounjaro available on the NHS for people with AF?
NHS access to tirzepatide is limited by specific BMI and comorbidity criteria, with eligibility that may vary by area.
AF alone isn’t a qualifying condition, but it’s often considered alongside other cardiovascular and metabolic factors. Your GP can clarify whether you’d qualify locally.
Take home message
You can take Mounjaro if you have AF. There’s no direct interaction with tirzepatide, no signal of increased arrhythmia in the SURMOUNT trial programme, and good evidence that the kind of weight loss Mounjaro supports reduces AF burden over time.
The practical points are working closely with your cardiologist, monitoring blood pressure and heart rate as your weight changes, and adjusting anticoagulant or rate-control doses if needed.
The lifestyle pieces, eating well, moving consistently, limiting alcohol, addressing sleep apnoea, and managing anxiety, are what sustain the changes over time.
Second Nature’s Mounjaro programme combines medication with support from registered dietitians and a structured habit-change programme.
It’s built around the balanced plate model (half vegetables, a quarter protein, a quarter complex carbohydrates, plus a serving of fat) and focuses on sustainable changes rather than restrictive dieting.
In a published study of Second Nature’s semaglutide-supported programme, active subscribers lost an average of 19.1% of their body weight at 12 months, with 77.7% achieving at least 10% weight loss.10
Second Nature's Mounjaro and Wegovy programmes
Second Nature provides Mounjaro or Wegovy as part of our Mounjaro and Wegovy weight-loss programmes.
Why choose Second Nature over other medication providers, assuming you're eligible?
Because peace of mind matters.
We've had the privilege of working with the NHS for over eight years, helping people across the UK take meaningful steps toward a healthier, happier life.
Our programmes are designed to meet people where they are, whether that means support with weight loss through compassionate one-to-one health coaching, or access to the latest weight-loss medications (like Mounjaro and Wegovy) delivered alongside expert care from a multidisciplinary team of doctors, psychologists, dietitians, and personal trainers.
At the heart of everything we do is a simple belief: real, lasting change comes from building better habits, not relying on quick fixes. We're here to support that change every step of the way.
With over a decade of experience, thousands of lives changed, and a long-standing record of delivering programmes used by the NHS, we believe we're the UK's most trusted weight-loss programme.
We hope to offer you something invaluable: peace of mind, and the support you need to take that first step.
References
- Pathak, R.K. et al. (2015). Long-term effect of goal-directed weight management in an atrial fibrillation cohort: a long-term follow-up study (LEGACY). Journal of the American College of Cardiology, 65(20), 2159-2169.
- Van Gelder, I.C. et al. (2024). 2024 ESC Guidelines for the management of atrial fibrillation developed in collaboration with the European Association for Cardio-Thoracic Surgery (EACTS). European Heart Journal, 45(36), 3314-3414.
- NHS. (2024). Atrial fibrillation.
- Jastreboff, A.M. et al. (2022). Tirzepatide once weekly for the treatment of obesity. New England Journal of Medicine, 387(3), 205-216.
- Aronne, L.J. et al. (2024). Continued treatment with tirzepatide for maintenance of weight reduction in adults with obesity: the SURMOUNT-4 randomised clinical trial. JAMA, 331(1), 38-48.
- Yang, Y. et al. (2024). Impact of a dual glucose-dependent insulinotropic peptide/glucagon-like peptide-1 receptor agonist tirzepatide on heart rate among patients with type 2 diabetes: a systematic review and pairwise and network meta-analysis. Diabetes, Obesity and Metabolism, 26(2), 548-556.
- National Institute for Health and Care Excellence. (2021). Atrial fibrillation: diagnosis and management (NG196).
- Lally, P. et al. (2010). How are habits formed: modelling habit formation in the real world. European Journal of Social Psychology, 40(6), 998-1009.
- Zhang, S. et al. (2024). Global epidemiology of mental disorder in atrial fibrillation between 1998-2021: a systematic review and meta-analysis. World Journal of Psychiatry, 14(1), 179-193.
- Richards, R. et al. (2025). A remotely delivered GLP-1RA-supported specialist weight management program in adults living with obesity: retrospective service evaluation. JMIR Formative Research, 9(1), e72577.
