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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Does Mounjaro Increase Heart Rate? Mounjaro vs Wegovy
Heart rate changes are a potential side effect with weight loss injections, but they're not equally common with all medications. If you're considering Mounjaro (tirzepatide) or Wegovy (semaglutide) in the UK, understanding how each medication may affect your heart rate is important. Both are prescription-only GLP-1 receptor agonists (Mounjaro is also a GIP agonist), and both can influence cardiovascular function differently. This guide compares the clinical evidence on heart rate effects and helps you understand what to expect.
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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.
Clinical Trial Evidence: Heart Rate Effects in SURMOUNT vs STEP
Heart rate changes were monitored differently in the SURMOUNT and STEP clinical trials. In SURMOUNT-1 (Mounjaro/tirzepatide), average heart rate increased by approximately 2–3 beats per minute across treatment groups, though this was typically modest and not considered a safety concern for most participants. In the STEP-1 trial (Wegovy/semaglutide), heart rate increases were similarly modest, averaging around 2–4 beats per minute.
Both medications can increase heart rate slightly because they may enhance metabolic rate and appetite suppression, particularly during rapid initial weight loss. However, neither drug directly stimulates the heart — the increases observed were generally mild and reversible. Individual responses vary significantly. Your GP or prescriber will monitor your heart rate and overall cardiovascular health before and during treatment to ensure safety.
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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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Who Should Be Cautious About Heart Rate Changes?
If you have a pre-existing heart condition — such as arrhythmia, tachycardia, or a history of heart attack or stroke — you should inform your prescriber before starting either Mounjaro or Wegovy. Some cardiovascular conditions may make heart rate monitoring more important. Adults with uncontrolled high blood pressure should also discuss this with their GP before starting weight loss injections.
The good news is that both medications are often prescribed specifically to adults with cardiovascular risk factors or existing conditions, because weight loss itself significantly reduces cardiovascular strain and disease risk. However, individual suitability must be assessed through a clinical consultation. Your prescriber will take a full cardiovascular history and may recommend more frequent monitoring if needed.
- 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.
Does Mounjaro increase heart rate more than Wegovy?
Clinical trial data shows both medications cause similar modest heart rate increases of 2–4 bpm on average. Mounjaro's dual GIP/GLP-1 mechanism doesn't appear to increase heart rate more than Wegovy's GLP-1-only mechanism. Individual variation is significant — some people experience no change, others a slight increase. Your prescriber will monitor your personal response.
Is an increased heart rate dangerous with Mounjaro or Wegovy?
Mild heart rate increases (2–4 bpm) observed in clinical trials were not considered dangerous for most adults. However, rapid or persistent tachycardia (elevated heart rate) should always be reported to your GP. This is why cardiovascular monitoring is part of the assessment and ongoing care with these medications.
Can I use Mounjaro if I already have a fast heart rate?
Yes, many people with tachycardia or arrhythmia use Mounjaro safely — but you must disclose this to your prescriber during the clinical assessment. They may recommend additional monitoring, dose adjustment, or exploration of underlying causes. Never start without discussing your cardiovascular history.
How does weight loss itself affect heart rate?
Losing weight typically reduces resting heart rate over time because your heart doesn't need to work as hard to pump blood. Initial weight loss can cause brief heart rate increases due to metabolic changes, but sustained weight loss generally improves cardiovascular health. This is why weight loss injections can benefit people with cardiovascular risk factors.
Should I monitor my heart rate while taking Mounjaro or Wegovy?
Your GP or prescriber will monitor your heart rate at appointments. You don't need to obsessively track it, but being aware of significant changes — like persistent rapid heartbeat, palpitations, or chest discomfort — is important. Report any concerning symptoms to your healthcare provider immediately.
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