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 Palpitations — A UK Health Guide
Palpitations (a fluttering or racing heartbeat sensation) are not listed as a common side effect of Mounjaro in the UK product information, though some people using GLP-1 and GIP/GLP-1 medications report noticing changes in heart rate or rhythm. This guide explains what the evidence shows, when to contact your GP, and how palpitations may relate to Mounjaro use. Always discuss any heart concerns with a healthcare professional before, during, or after starting any weight management medication.
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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.
What Does the Evidence Show About Mounjaro and Palpitations?
Palpitations are not listed as a very common or common side effect of Mounjaro (tirzepatide) in UK clinical data, though individual experiences vary. During the SURMOUNT clinical trials, palpitations were not reported as a primary concern. However, because Mounjaro affects heart rate regulation through GIP and GLP-1 pathways, some users report noticing their heartbeat, particularly during the initial dose escalation or when increasing doses.
Important context: Palpitations can occur for many reasons — anxiety, caffeine intake, dehydration, or underlying heart conditions — not just medication. If you experience new or persistent palpitations after starting Mounjaro, contact your GP rather than assuming they are medication-related. Your prescriber needs to assess whether the symptom is connected to the injection or another cause entirely.
- Report palpitations to your GP even if mild or infrequent
- Do not stop Mounjaro without medical guidance
- Keep a brief log of when palpitations occur and what you were doing
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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 Should You Seek Medical Advice About Palpitations?
Contact your GP or call NHS 111 if you experience new palpitations after starting Mounjaro, especially if accompanied by chest pain, shortness of breath, dizziness, or fainting. These symptoms warrant urgent evaluation. If palpitations are brief, isolated, and you feel otherwise well, note them and mention them at your next appointment — but do not delay if symptoms feel concerning or are worsening.
Be honest with your prescriber about all symptoms, including when they started and how often they occur. Your medical history matters: if you have any pre-existing heart conditions, irregular heartbeat, or high blood pressure, your GP needs to know this affects how Mounjaro may be managed for you. Use our free BMI calculator and GLP-1 weight loss calculator to track your overall health metrics alongside any symptoms you experience.
- 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 palpitations a common side effect of Mounjaro?
Palpitations are not listed as a very common or common side effect of Mounjaro in UK product information. However, individual experiences vary. Some users report noticing their heartbeat, particularly during dose escalation. Always report any new symptoms to your GP rather than assuming they are medication-related, as palpitations can have many causes.
Can Mounjaro cause heart problems?
Mounjaro affects heart rate regulation through its GIP and GLP-1 mechanisms, which is why heart rate changes are theoretically possible. However, serious heart problems are not a known primary risk. Clinical trials did not highlight heart problems as a major concern. If you have pre-existing heart conditions or high blood pressure, your GP will assess whether Mounjaro is suitable for you.
What should I do if I develop palpitations while taking Mounjaro?
Contact your GP, especially if palpitations are new, frequent, or accompanied by chest pain, shortness of breath, or dizziness. Do not stop Mounjaro without medical guidance. Your GP will assess whether palpitations are related to the medication or another cause, and will advise whether to continue, adjust, or change your treatment.
How does Mounjaro affect heart rate?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist. GLP-1 activation can influence heart rate through multiple pathways, including effects on blood pressure and glucose control. In clinical trials, mean heart rate changes were modest and not considered a safety concern, but individual responses vary based on overall health and existing conditions.
Should I avoid Mounjaro if I have heart palpitations already?
Not necessarily — but you must inform your prescriber. If you already experience palpitations, your GP will take this into account when assessing whether Mounjaro is suitable for you. Some people with existing palpitations use Mounjaro safely with close monitoring. Others may need a different approach. Always have this conversation before starting treatment.
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