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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How to Monitor Mounjaro Safely in the UK
If you're taking Mounjaro (tirzepatide) in the UK, regular monitoring by your healthcare provider is essential to ensure the medication is working safely and effectively for you. Whether you're prescribed through NHS specialist services or a private online clinic, understanding what monitoring involves and what to watch for helps you get the most from your treatment. This guide explains NHS monitoring standards, what your GP will check, and when to seek urgent medical attention.
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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.
NHS Monitoring Standards and Follow-Up
The NHS requires regular clinical monitoring for all patients taking Mounjaro, typically every 4 weeks initially and then every 8–12 weeks once stable. Your GP or specialist will check your weight, blood pressure, and how you're tolerating the medication. Blood tests may be arranged to monitor blood sugar levels (if you have type 2 diabetes), kidney function, and pancreatic health — particularly important given the gastrointestinal side effects Mounjaro can cause.
During each appointment, your healthcare provider will discuss:
- Weight loss progress and how it compares to your treatment goals
- Any side effects you're experiencing — nausea, vomiting, constipation, or stomach pain
- Dose adjustments if needed (Mounjaro is typically escalated over 16+ weeks from 2.5 mg to a maximum of 15 mg weekly)
- How well you're managing diet and physical activity alongside the injection
- Any changes to other medications you take
This structured approach ensures your safety while optimising the effectiveness of your tirzepatide treatment. Your prescriber will also discuss what to do if you miss a dose or experience concerning 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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
What to Watch For and When to Seek Urgent Help
Most Mounjaro side effects are mild to moderate and settle over time, but certain symptoms require urgent medical attention. Seek emergency care immediately if you experience severe, persistent stomach pain spreading to your back (possible pancreatitis), serious allergic reactions with facial swelling or breathing difficulty, or changes in your vision. Contact your GP within 24 hours if you develop signs of gallbladder problems (sharp pain in the upper stomach), severe vomiting lasting more than a few hours, or signs of dehydration.
Between appointments, use our free BMI calculator and progress tracker to log your own weight loss journey — this helps you spot patterns and prepares you for your monitoring appointments. Keep a brief diary of any side effects or concerns to discuss with your GP, as this information helps your prescriber make informed decisions about dose adjustments or alternative treatments 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.
How often will my GP monitor me on Mounjaro in the UK?
Initial monitoring is typically every 4 weeks while your dose is being increased (weeks 1–16+), then every 8–12 weeks once you're on a stable maintenance dose. Your NHS specialist service or private prescriber will arrange these appointments. The exact schedule depends on your individual health needs and how well you're tolerating the medication.
What blood tests might my GP arrange while I'm taking Mounjaro?
Your GP may check blood sugar levels (HbA1c if you have diabetes), kidney function (creatinine, eGFR), liver function, and pancreatic enzymes (amylase, lipase) — particularly if you report stomach pain. These tests help detect any medication-related changes early. The frequency depends on your health profile and any existing conditions.
What stomach symptoms should I report to my GP immediately?
Seek urgent care for severe, persistent stomach pain spreading to your back (possible pancreatitis), vomiting lasting more than a few hours, or signs of gallbladder problems (sharp upper stomach pain). Mild nausea, constipation, and indigestion are common but should still be mentioned at your monitoring appointment so your dose can be adjusted if needed.
Can I monitor my own weight loss between GP appointments?
Yes — tracking your own progress helps you prepare for appointments and spot any concerning patterns. Use our free progress tracker to log weekly or fortnightly weights, or keep a simple record. However, this cannot replace professional monitoring — your GP needs to check blood pressure, arrange blood tests, and assess side effects regularly.
What happens if I miss a dose of Mounjaro?
If you miss a dose within 4 days, take it as soon as you remember and continue your normal weekly schedule. If it's more than 4 days late, skip that dose and take your next dose on your usual day. Never double-dose. Inform your GP at your next monitoring appointment so they can advise on whether to adjust your schedule.
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.