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
Why Has Your Weight Loss Stalled?
Weight loss plateaus are common and frustrating, but they are not permanent. When your weight stops changing despite effort, your body may be adapting to calorie reduction, or your current approach needs adjustment. Understanding why plateaus happen—and what to do about them—can help you restart progress. This guide covers evidence-based strategies used in NHS weight management and practical steps to overcome stagnation.
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Calculate Your BMI Instantly
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.
Common Reasons Weight Loss Stalls
Weight loss plateaus typically happen for several reasons:
- Adaptive thermogenesis: Your body adjusts to lower calorie intake by burning fewer calories at rest. This is a normal metabolic response.
- Loss of lean muscle: gradual weight management without resistance exercise can result in muscle loss, which lowers your resting metabolic rate.
- Reduced calorie deficit: As you lose weight, your daily calorie needs decrease—the same deficit that worked at your starting weight may no longer create progress.
- Hormonal changes: Prolonged calorie restriction can affect hormones like leptin and cortisol, which influence appetite and fat storage.
- Medication tolerance: If using GLP-1 weight loss medication like Wegovy or Mounjaro, your body may adapt over weeks or months, requiring dose adjustment by your prescriber.
- Adherence drift: Over time, portion sizes may gradually increase or physical activity may decrease—small changes that plateau weight loss.
The good news: plateaus are normal, temporary, and manageable with the right adjustments.
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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.
Practical Steps to Restart Weight Loss
Increase physical activity: Add resistance training 2–3 times per week to preserve muscle mass and increase your resting metabolic rate. Even 20–30 minutes of brisk walking daily can help.
Reassess your calorie intake: Recalculate your daily calorie needs based on your current weight—you may need to reduce calories slightly, but avoid dropping below 1200 kcal/day without GP supervision.
Vary your routine: Change your exercise type, meal timing, or macronutrient balance to prevent metabolic adaptation.
Check medication dosage: If taking prescription weight loss medication, speak to your prescriber about whether a dose adjustment might help restart progress.
Review lifestyle factors: Ensure you're sleeping 7–9 hours nightly, managing stress, and staying hydrated—all affect weight management. Calculate your personal BMI using our free BMI calculator to track your progress from where you are now.
- 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 weight loss plateau typically last?
Plateaus usually last 2–4 weeks, but can extend longer depending on the cause. If you see no change for more than 4 weeks despite consistent effort, it's time to adjust your approach. Keep a progress record using our free progress tracker to distinguish true plateaus from normal weight fluctuation.
Should I eat fewer calories to break a plateau?
Not necessarily. Eating very little often backfires—it increases hunger, muscle loss, and metabolic slowdown. Instead, focus on adding exercise, changing meal timing, or checking protein intake. Never drop below 1200 kcal/day without your GP's guidance.
Can GLP-1 medication like Wegovy or Mounjaro help restart weight loss after a plateau?
If you're already on prescription weight loss medication, a dose increase might help—Wegovy ranges from 0.25mg to 2.4mg weekly, and Mounjaro from 2.5mg to 15mg weekly. Your prescriber can assess whether adjustment is appropriate. If not on medication, eligibility for GLP-1 treatment depends on your BMI and health factors—your GP can advise.
Is weight loss plateauing a sign my body weight is "set"?
No. The set point theory is not supported by current evidence. Plateaus reflect metabolic adaptation and are temporary. Changing your calorie intake, exercise routine, or medication dose can restart progress. Sustainable weight loss requires patience and adjustment, not dramatic restriction.
What role does the NHS play in managing weight loss plateaus?
Your GP can refer you to NHS weight management services (Tier 2 or 3), where dietitians and behaviour change specialists help break plateaus through tailored strategies. For prescription weight loss medication like Mounjaro or Wegovy, NHS specialist services can manage adjustments. Private online prescribing is also available in the UK. ```
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.