The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
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Heart Palpitations On Mounjaro — What You Need To Know
Palpitations (feeling your heart racing or beating irregularly) are not listed as a common side effect of Mounjaro in UK clinical trials, but some people report experiencing them. If you develop palpitations after starting tirzepatide, it's important to understand what's happening, when to contact your GP, and how this fits within NHS prescribing guidance. This guide covers the facts, what the evidence shows, and practical next steps if you're experiencing this on Mounjaro.
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Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
Palpitations On Mounjaro — What The Evidence Shows
Palpitations are not listed as a common or very common side effect in the SURMOUNT clinical trials that led to Mounjaro's UK approval. The most frequently reported side effects are nausea, diarrhoea, vomiting, and constipation. However, palpitations can occur occasionally and may be related to several factors:
- gradual weight management: Losing weight quickly can temporarily increase heart rate and cause palpitations, particularly if you're restricting calories significantly alongside tirzepatide
- Dehydration: GLP-1 agonists like Mounjaro can reduce appetite, sometimes leading to reduced fluid intake — dehydration triggers palpitations
- Electrolyte imbalance: gradual weight management and changes in eating patterns can affect sodium and potassium levels, affecting heart rhythm
- Underlying cardiovascular risk: People with existing heart conditions or risk factors may be more susceptible to palpitations when on tirzepatide
- Anxiety or stress: Some people report anxiety-like symptoms on GLP-1 medications, which can cause palpitations
If you experience palpitations on Mounjaro, contact your GP or NHS 111 for guidance — do not ignore persistent symptoms.
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
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When To Seek Urgent Medical Attention
Seek immediate medical help (call 999 or go to A&E) if you experience:
- Chest pain or pressure alongside palpitations
- Severe shortness of breath
- Fainting or dizziness with palpitations lasting more than a few minutes
- Palpitations accompanied by confusion or weakness
For less urgent concerns, contact your GP or call NHS 111 for advice. They can assess whether your palpitations are related to Mounjaro or another cause, and discuss whether continuing tirzepatide is safe for you. Your prescriber may adjust your dose, pause treatment, or investigate further depending on the cause. Calculate your BMI using our free tool above to discuss your weight management options with your GP if you need to stop Mounjaro.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
Are palpitations a known side effect of Mounjaro?
Palpitations are not listed as common or very common in SURMOUNT clinical trials, though they can occur occasionally. They're more often related to gradual weight management, dehydration, or electrolyte changes than to tirzepatide itself. Always report them to your GP for proper assessment.
What should I do if I develop palpitations after starting Mounjaro?
Contact your GP or NHS 111 for guidance. Do not ignore persistent symptoms. Your prescriber will assess the cause and decide whether to continue, pause, or adjust your Mounjaro dose. In the meantime, ensure you're drinking enough water and eating balanced meals.
Can gradual weight management on Mounjaro cause palpitations?
Yes. Losing weight very quickly can increase heart rate and trigger palpitations. The NHS recommends losing no more than 0.5–1 kg per week for safe, sustainable weight loss. If you're losing faster, discuss with your GP — you may need to adjust your calorie intake.
Should I stop taking Mounjaro if I get palpitations?
Do not stop without consulting your prescriber. Some causes (like dehydration) are easily fixed and don't require stopping the medication. Others may require a pause or dose adjustment. Your GP will advise based on the cause and severity.
What's the difference between normal heart racing and dangerous palpitations on Mounjaro?
Brief palpitations after exercise or anxiety are usually normal. Concerning signs include palpitations at rest, lasting minutes, accompanied by chest pain, shortness of breath, or dizziness. If in doubt, contact NHS 111 — it's always better to get assessed than worry.
Ready to take control of your weight loss journey?
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