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
Free tracker included with every download this week
What to Monitor While Taking Mounjaro
If you're taking Mounjaro (tirzepatide), regular monitoring helps ensure the medication is working safely for you. Monitoring involves tracking your weight, side effects, how you're feeling, and certain health markers with your GP or prescriber. This guide explains what to check, how often, and when to seek medical advice during your Mounjaro treatment in the UK.
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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.
Key Health Markers to Track
While taking Mounjaro, your prescriber will want you to monitor several important health markers alongside your weight:
- Body weight: Weigh yourself weekly at the same time of day. Log your progress using a free progress tracker to spot trends across weeks and months.
- Blood pressure: If you have hypertension, check your BP regularly. Weight loss often improves blood pressure, but your GP may need to adjust medications.
- Blood sugar levels: If you have type 2 diabetes or prediabetes, continue monitoring as directed by your GP — Mounjaro may improve glucose control.
- Cholesterol and lipids: Your prescriber may recommend periodic blood tests to check lipid profile improvements.
- Waist circumference: Measure around your waist at the level of your navel monthly. This tracks visceral fat loss, which matters for health even if weight loss plateaus.
Your GP or prescriber will advise which markers are most relevant to your personal health situation.
Clinically BackedWeight Loss
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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.
Side Effects and Symptom Tracking When to Contact Your Prescriber or GP
Monitor for common side effects, especially in the first 4–8 weeks as your body adjusts to each new Mounjaro dose. Nausea, diarrhoea, constipation, and stomach pain are common — most improve over time. Keep a simple log of which symptoms occur, when, and how severe they are; this helps your prescriber decide whether to increase your dose or adjust timing. Seek urgent medical advice if you experience severe, persistent stomach pain (possible pancreatitis), changes in vision, severe vomiting that prevents you eating or drinking, or signs of allergic reaction (swelling of face, lips, or throat). Contact your GP within a few days if side effects are affecting your quality of life or if you're concerned about any aspect of your treatment.
- 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 should I weigh myself while taking Mounjaro?
Weekly weighing at the same time of day is ideal for spotting trends. Daily weighing can be misleading because weight fluctuates naturally. Use our free progress tracker to log weekly weights and visualise your progress over weeks and months, which is more meaningful than day-to-day changes.
Will my GP monitor my Mounjaro automatically?
If you're prescribed Mounjaro through NHS specialist services, you'll have regular follow-up appointments where they check your weight, blood pressure, and general health. If you're prescribed privately, your prescriber will give you a monitoring schedule. Either way, you should report new symptoms or concerns between appointments.
What blood tests do I need while taking Mounjaro?
Your prescriber will advise which tests are needed based on your health conditions. If you have diabetes, they may check HbA1c (blood sugar control). If you have high cholesterol, lipid panels may be monitored. Liver and kidney function may also be checked periodically, especially if you have existing conditions.
How long does it take to see weight loss on Mounjaro?
Most people notice initial changes within 2–4 weeks, though this varies. Average weight loss in clinical trials was approximately 15–21% of body weight over 72 weeks, but individual results vary significantly. Weight loss typically continues as your dose increases and plateaus after several months.
Should I stop Mounjaro if I develop side effects?
No — contact your prescriber first. Many side effects are temporary and improve as your body adjusts. Your prescriber may recommend taking your injection at a different time of day, adjusting your diet, or delaying a dose increase. Never stop Mounjaro without medical guidance.
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.