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
How Long Do Weight Loss Plateaus Last?
Weight loss plateaus are a completely normal part of the weight management journey — your body adapts to dietary and activity changes, and progress temporarily slows or stops even though you're doing everything right. Most plateaus last between 4 to 8 weeks, though some can persist longer depending on your individual circumstances, starting weight, and metabolism. Understanding why plateaus happen and what you can do about them helps you stay motivated and keep progressing 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 lose weight, your body adapts metabolically. Your basal metabolic rate (the calories your body burns at rest) decreases as you weigh less — simply because a smaller body requires less energy to function. Additionally, as you lose weight, you may need to further reduce your calorie intake to maintain the same deficit, because that 500 kcal deficit that worked at your starting weight may no longer be sufficient at your new, lower weight.
Your nervous system also adapts. Hormones like leptin (which signals fullness) and ghrelin (which signals hunger) fluctuate, and your body may increase appetite signals to try to restore its previous weight. Fluid retention, hormonal cycles, and even gut bacteria changes can mask fat loss on the scales, making it seem like progress has stopped when it hasn't. This is why the NHS recommends looking beyond the scales — measuring waist circumference, how clothes fit, and energy levels are equally valid measures of progress during a plateau.
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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.
Breaking Through a Plateau
If your plateau lasts longer than 8 weeks, consider these evidence-based strategies: increase physical activity (adding strength training helps preserve muscle mass during weight loss), adjust your calorie intake downward by 10–15% (not drastically), or vary your exercise routine to challenge your body differently. Some people find success with intermittent fasting or changing their meal timing.
For those using GLP-1 weight loss medication like Wegovy or Mounjaro, a plateau may signal that your current dose has reached its effectiveness — your prescriber can assess whether a dose increase is appropriate. Track your progress with our free progress tracker to spot trends beyond daily weight fluctuations, and use our BMI calculator and weight converter to monitor changes in context.
If your plateau lasts longer than 8 weeks, consider these evidence-based strategies: increase physical activity (adding strength training helps preserve muscle mass during weight loss), adjust your calorie intake downward by 10–15% (not drastically), or vary your exercise routine to challenge your body differently. Some people find success with intermittent fasting or changing their meal timing. For those using GLP-1 weight loss medication like Wegovy or Mounjaro, a plateau may signal that your current dose has reached its effectiveness — your prescriber can assess whether a dose increase is appropriate. Regular monitoring using our free progress tracker helps you spot trends beyond daily weight fluctuations and stay motivated through plateaus.
- 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 a weight loss plateau normal?
Yes, completely normal. Your body adapts metabolically to dietary changes, hormone levels fluctuate, and fluid retention masks fat loss. Most plateaus last 4–8 weeks. Consulting your GP or a registered dietitian can help you determine whether your plateau is metabolic adaptation or whether you need to adjust your approach.
Should I eat less if I hit a plateau?
Not drastically. If you're already in a calorie deficit, dropping calories too low is unsustainable and can harm muscle mass. The NHS recommends a 500 kcal deficit for steady loss, but as you weigh less, you may need to reduce this further. A small 10–15% adjustment is often enough — your GP or dietitian can advise.
Does exercise help break a plateau?
Yes. Adding strength training preserves muscle mass and increases metabolic demands. Even increasing daily movement (more walking, stairs) can help. Varying your exercise routine challenges your body differently and may reignite progress. Combined with dietary consistency, exercise is most effective for breaking plateaus.
Can weight loss medications help with plateaus?
If you're taking GLP-1 weight loss medication like Wegovy or Mounjaro, a plateau may mean your current dose has reached its effectiveness plateau. Your prescriber may assess whether increasing your dose is appropriate — this requires clinical judgment based on your individual response and health status.
How do I know if my plateau is temporary or permanent?
Track more than just weight — measure waist circumference, track energy levels, and how clothes fit. Weigh yourself weekly at the same time, not daily (water retention causes daily fluctuations). If no progress appears for 12+ weeks despite consistent effort, speak with your GP. Most plateaus resolve within 8 weeks with patience and minor adjustments.
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.