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 Is a Weight Loss Plateau and How Do You Break Through It?
A weight loss plateau occurs when your weight stops decreasing despite continuing your diet and exercise routine. This is completely normal and happens to most people during their weight management journey. Plateaus typically last between 2 to 8 weeks, though some last longer. Understanding why plateaus happen — and knowing practical strategies to overcome them — helps you stay motivated and continue making progress towards your health goals.
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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.
Why Weight Loss Plateaus Happen
When you first start losing weight, your body adapts to the calorie deficit. Your metabolic rate gradually decreases because your body requires fewer calories to maintain a smaller mass. Additionally, as you lose weight, you lose both fat and muscle tissue — muscle burns more calories at rest than fat, so losing muscle reduces your overall energy expenditure.
Other factors contributing to plateaus include:
- Hormonal changes: Reduced leptin (fullness hormone) and increased ghrelin (hunger hormone) can make you feel hungrier and less satisfied
- Water retention: Fluid shifts can mask fat loss on the scales for weeks
- Adaptation: Your body becomes more efficient at your current exercise routine, burning fewer calories
- Inconsistent adherence: Gradual increases in portion sizes or reduced activity often occur unconsciously
The good news: plateaus are temporary and indicate your body is adjusting, not that weight loss has stopped permanently.
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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.
Proven Strategies to Break Through a Weight Loss Plateau
Reassess your calorie intake: Use your free progress tracker to log food for 3–5 days and check whether portion sizes have crept up. A small additional deficit of 100–200 kcal per day may help restart progress.
Increase physical activity: Add strength training to preserve muscle mass during weight loss. Even 20 minutes of resistance work 2–3 times weekly helps. Alternatively, increase daily movement through walking or cycling.
Consider prescription weight management: If lifestyle changes alone aren't breaking the plateau, your GP can assess whether prescription weight loss medication — such as GLP-1 injections — might support your efforts. These work through appetite regulation and may help when combined with reduced-calorie diet and exercise.
Be patient: If your plateau has lasted less than 4 weeks, continue your current approach. Many plateaus resolve naturally.
- 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 long does a typical weight loss plateau last?
Most weight loss plateaus last 2 to 8 weeks. Some may persist longer, especially if you've already lost a significant amount of weight. During this time, your body is adjusting metabolically — fat loss may still be occurring even if the scale isn't moving. If a plateau extends beyond 12 weeks without any progress, it's worth speaking to your GP about your approach.
Should I worry if my weight plateaus during Wegovy or GLP-1 treatment?
No. Plateaus are normal even with prescription weight management medication. GLP-1 medications like Wegovy work by reducing appetite and supporting calorie deficit — they don't prevent the biological adaptation that causes plateaus. Continue your diet and exercise routine, stay hydrated, and speak to your prescriber if the plateau lasts beyond 8 weeks. Many people see renewed progress after a brief pause.
Can I break a weight loss plateau by eating less?
Not always. Eating too little can slow your metabolism further and make plateaus worse. The NHS recommends a sustainable calorie deficit of around 500 kcal per day for 0.5kg weekly loss. If you're already at this level, focus on increasing activity and checking protein intake (which preserves muscle) rather than cutting calories further. Your GP can advise on safe approaches.
Does water retention cause weight loss plateaus?
Yes — water retention can mask fat loss on the scales for 1–4 weeks, especially after increasing exercise (which causes temporary muscle inflammation and fluid retention). This is not fat regain. Continue your healthy habits, stay hydrated, and the scale will usually catch up. Using our free progress tracker alongside body measurements (waist, chest) helps you see progress beyond weight alone.
When should I speak to my GP about a plateau?
Contact your GP if you've hit a plateau for more than 12 weeks with no progress despite consistent diet and exercise, or if you're losing weight very rapidly (more than 1kg per week), which can indicate muscle loss. Your GP can check for underlying health issues (thyroid problems, medications affecting weight) and discuss whether NHS weight loss support or prescription weight management medication might help you break through.
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.