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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Mounjaro and Increased Heart Rate — What You Need to Know
An increased heart rate (tachycardia) is not listed as a common side effect of Mounjaro (tirzepatide) in clinical trials, but some people using GLP-1 and dual GIP/GLP-1 receptor agonist medications report heart palpitations or a faster heartbeat. If you experience a noticeably elevated heart rate while taking Mounjaro, it's important to understand what might be causing it and when to contact your GP. This guide explains the connection between Mounjaro and heart rate changes, how to monitor your symptoms, and what your prescriber needs to know.
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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.
Heart Rate Changes and Mounjaro — What the Evidence Shows
Heart rate elevation is not reported as a very common or common side effect in the SURMOUNT clinical trials for tirzepatide (Mounjaro). However, some individuals do report palpitations or increased heart rate when using GLP-1 receptor agonist medications, including semaglutide (Wegovy) and liraglutide (Saxenda). Several factors may contribute to heart rate changes during Mounjaro treatment:
- Dehydration — GLP-1 medications can cause nausea and vomiting, leading to fluid loss and a compensatory increase in heart rate
- Blood sugar regulation — As blood glucose stabilises, heart rate patterns may change temporarily
- Dose escalation — Heart palpitations may occur during the dose titration phase (weeks 1–20) as your body adjusts
- Anxiety or stress response — Weight loss medication use can trigger psychological responses that elevate heart rate
- Underlying cardiovascular conditions — Pre-existing heart conditions may react differently to medication
If you notice a sustained increase in resting heart rate or frequent palpitations, contact your GP or prescriber promptly rather than stopping the medication suddenly.
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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 Medical Advice and How to Access Support in the UK
You should contact your GP or prescriber urgently if you experience chest pain, severe shortness of breath, fainting, or a very rapid heartbeat (over 120 beats per minute at rest). These may indicate a more serious condition requiring immediate assessment. For ongoing heart rate concerns, your GP can arrange an ECG (electrocardiogram) or Holter monitor test to check your heart rhythm and rule out complications. Document your resting heart rate for a few days before your appointment — this information helps your prescriber assess whether the heart rate change is related to Mounjaro or another cause. Many people successfully manage Mounjaro while monitoring heart health through regular check-ups and lifestyle adjustments like staying hydrated and managing stress.
- 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.
Is increased heart rate a known side effect of Mounjaro?
Tachycardia is not listed as a common side effect in clinical trials, but some people report palpitations. Dehydration, dose escalation, and underlying health conditions may contribute. Always report heart rate changes to your prescriber.
What's a normal heart rate while taking Mounjaro?
Normal resting heart rate for adults is 60–100 beats per minute. If your resting rate increases by 10–20 bpm from your baseline or exceeds 100 bpm consistently, mention it to your GP, especially if accompanied by symptoms.
Can I use our free BMI calculator to track my progress while monitoring heart health?
Yes, tracking your BMI and weight loss progress using our BMI calculator and progress tracker can help you see overall health improvements. Share these records with your prescriber during health assessments.
How does Mounjaro access work in the UK if I have heart concerns?
Whether you access Mounjaro via NHS specialist services or private prescription following an online consultation, your prescriber will review your full health history, including heart conditions, before issuing a prescription. Always disclose cardiovascular concerns.
Should I stop taking Mounjaro if my heart rate increases?
Do not stop suddenly without medical guidance — abrupt cessation may cause other complications. Contact your prescriber instead. They can adjust your dose, investigate the cause, or discuss alternative weight management options if needed.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.